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Discussion Starter #1
One of my upcoming projects is to tackle the A/C system on my '92 Bronco.

I bought the truck this past summer and the A/C although complete does not work. Not worried about why really the current system does not function as probably no A/C charge. Never even bothered to check it out. This system is still a freon 12 system and has never been upgraded to the 134a.

Considering that my plans are to keep this truck long term (10+ years) when I redo the system I will do a 134 system due to how scarce and expensive it is to source any r12 even today. I can still get r12 right now but you are looking at about 25.00 per 12oz can!

In the past I have "converted" 12 systems to 134 and they work great running down the road but in heavy stop and go traffic and only being able to use about an 80% charge on the 134 due to system pressures the performance of such converted systems seems to leave a lot to be desired as far as maintaing adequate cooling in those excessive sitting at stoplights in heavy traffic situations so I am looking for a better upgrade path.

So what I have been considering as a possible option is to install a complete new system but buying parts for say a 95 or so where the 134 was the factory installed refrigerant and then the cooling performance in theory should be good in all situations.

I am talking about new compressor, condensor, drier, hoses, evaporator, pressure switches, orifice basically the entire system. Just doing some parts specs comparing it does seem as if the newer factory 134 systems evaporator is slightly larger than the older R12 systems.

What I am wondering is if anyone knows whether the underhood evaporator box is different on the newer 94+ systems or whether the newer evaporator would possibly still fit in the '92's box?

I am just speculating but considereing the trucks changed very little in the last years I am hoping that it may be fairly easy to adapt the later model pieces to the slightly earlier truck.

Is my logic correct that by upgrading to the complete newer factory system that is designed for the 134a that I should be able to duplicate the newer vehicles ac performance including heavy traffic situations?

I have a '94 Dodge Dakota that came with the factory 134 system and that system performs extremely well in all situations.

Any way I go will probably be about the same cost wise as I will be replacing all the componants in the system as I want to do this once and have dependable, basically leak and trouble free ice cold AC for some time

Anybody that can shed some light your response is appreciated. Thanks
 

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One of my upcoming projects is to tackle the A/C system on my '92 Bronco.

I bought the truck this past summer and the A/C although complete does not work. Not worried about why really the current system does not function as probably no A/C charge. Never even bothered to check it out. This system is still a freon 12 system and has never been upgraded to the 134a.

Considering that my plans are to keep this truck long term (10+ years) when I redo the system I will do a 134 system due to how scarce and expensive it is to source any r12 even today. I can still get r12 right now but you are looking at about 25.00 per 12oz can!

In the past I have "converted" 12 systems to 134 and they work great running down the road but in heavy stop and go traffic and only being able to use about an 80% charge on the 134 due to system pressures the performance of such converted systems seems to leave a lot to be desired as far as maintaing adequate cooling in those excessive sitting at stoplights in heavy traffic situations so I am looking for a better upgrade path.

So what I have been considering as a possible option is to install a complete new system but buying parts for say a 95 or so where the 134 was the factory installed refrigerant and then the cooling performance in theory should be good in all situations.

I am talking about new compressor, condensor, drier, hoses, evaporator, pressure switches, orifice basically the entire system. Just doing some parts specs comparing it does seem as if the newer factory 134 systems evaporator is slightly larger than the older R12 systems.

What I am wondering is if anyone knows whether the underhood evaporator box is different on the newer 94+ systems or whether the newer evaporator would possibly still fit in the '92's box?

I am just speculating but considereing the trucks changed very little in the last years I am hoping that it may be fairly easy to adapt the later model pieces to the slightly earlier truck.

Is my logic correct that by upgrading to the complete newer factory system that is designed for the 134a that I should be able to duplicate the newer vehicles ac performance including heavy traffic situations?

I have a '94 Dodge Dakota that came with the factory 134 system and that system performs extremely well in all situations.

Any way I go will probably be about the same cost wise as I will be replacing all the componants in the system as I want to do this once and have dependable, basically leak and trouble free ice cold AC for some time

Anybody that can shed some light your response is appreciated. Thanks
I'm no expert so don't take what I have to say as gospel. I don't think that the components are different at all as far as function goes. There might be differences in mounting. The evaporator would have to mount in the 92's box on the firewall, and the dryer, hoses and compressor are all the same. I have heard that there is a different style of condensor, but I'd have to go back and find out where I read about that.

As far as poor cooling in stop and go traffic, I think that the 2 speed e-fan is the answer for that.

Here's what I did. Replace hoses, filter, dryer, compressor and condensor. Flush and vacuum test the evaporator, and if it holds vacuum reuse it. It's just a pita to replace if it's not leaking. Dryer, condensor, hoses and filter cost about $200. Add the compressor with clutch and your ready to go. Oh, and the r12 to r134 valve conversion kit.
 

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Check out my A/C Rebuild thread here.
http://www.fullsizebronco.com/forum/showthread.php?t=200136

I replaced every component of my system. I still have 2 pieces left though, the High and low Switch and the respective pigtails.

I beleive the 92 system uses the same components other than the hose. Im pretty sure the hose is slightly different. Pressure sensors probly are as well.
The difference is, you have to flush the piss out of it to get every drop of the R-12 oil out of it as its not compatible with the 134a.
I would just replace everything. Its easy, and you know it will be 100% correct. My A/C just about blows snow out the vents now.
 

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The condenser is different between the R12 and R134a systems. Factory R134a systems use a physically larger condenser as well as construction. Everything else is pretty much the same. Factory R134a systems use a high pressure cut-off switch whereas a R12 system does not. Depending on the condition of the hoses I would seriously consider a R12 equivalent replacement refrigerant versus a R-134a conversion based on your criteria of long term ownership.
 

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Discussion Starter #6
Check out my A/C Rebuild thread here.
http://www.fullsizebronco.com/forum/showthread.php?t=200136

I replaced every component of my system. I still have 2 pieces left though, the High and low Switch and the respective pigtails.

I beleive the 92 system uses the same components other than the hose. Im pretty sure the hose is slightly different. Pressure sensors probly are as well.
The difference is, you have to flush the piss out of it to get every drop of the R-12 oil out of it as its not compatible with the 134a.
I would just replace everything. Its easy, and you know it will be 100% correct. My A/C just about blows snow out the vents now.
I have looked at your build and you did a nice job. As far as componants are concerned comparing part numbers the only part number that is the same between the 92 model system and a 95 model system is the replacement compressor itself which list as being used on the 90 thru 97 systems.

The rest of the system seems to change part numbers in the 94 model year which probably is the year that Ford switched over to the 134 systems. (my Dakota is a 94 and was a first year 134 system for Dodge)

Now whether those changes are a result of the hose ends or connections changing styles or something of that nature I am not really sure at this point. I think the condensor is also thicker but need to research that a bit more. But I do know that the evaporator is of a slightly bigger physical size.

This is where my biggest question is does anybody know if the underhood box that holds the evaporator changed or if the later evaporator will fit in the 92 box?

My thoughts on this is that from doing previous 134 conversions that because of the higher operating pressures of the 134 vs the r12 that when you recharge a system with 134 that was designed for r12 refrigerant that you only use about an 80% charge volumn as compared to the r12 volumn to keep the operating pressures within a safe range for the system.

Now from what I have experienced on a day in the 80's everything works fine and feels great but when the temps start creeping up into the mid 90's then running down the road it works fine but sitting in city traffic there is a noticeable rise in temps coming out of the vents until you get rolling again. I just speculate that this is partly from the result of needing to use a smaller amount of refrigerant to charge the system.

As it seems the condensor is slightly larger and the evaporator is also slightly larger on the factory 134 based systems then it seems that increasing the system capacity to be able to get a slightly larger charge volumn using the 134 refrigerant may be all that was required to get the 134 to perform as well in all conditions like the r12 in the slightly smaller capacity systems.

My plans are that when I replace the system regardless of which way I go that all componants in the system will be replaced new. So as far as cost this will be within a very few dollars difference either way.

I know some people will consider this a waste of dollars but as I do things I want to be able to do the job one time and hopefully be done needing to perform service in that area for a long time. This is for a couple of reasons actually as I have gotten older I do not mind spending the money to get something right and no longer want a vehicle that I constantly have to go back and work on the same systems over and over.

Also I have some health issues that as of now I can still perform the services myself and my cash outlay is basically a parts only at the present time but in the future a few years from now I will probably not be in the condition I can do the work myself any longer and at that point needing to start paying for the labor as well repair cost will escalate greatly so the more thorough my repairs and replacements are done now the cheaper they will be be in the long run.
 

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Discussion Starter #7
The condenser is different between the R12 and R134a systems. Factory R134a systems use a physically larger condenser as well as construction. Everything else is pretty much the same. Factory R134a systems use a high pressure cut-off switch whereas a R12 system does not. Depending on the condition of the hoses I would seriously consider a R12 equivalent replacement refrigerant versus a R-134a conversion based on your criteria of long term ownership.
Hoses will be replaced either way so that really will not be a concern.

I can actually still obtain r12 at the present time although the cost is not really cheap. Would cost about a 100.00 to fill an empty ac system.

My concern going this route though would be that although I could put a little extra r12 back to "have in stock" that down the road I could end up back where I am now if the system developed a leak or had to be opened for some reason and there was no more r12 to be had.

The 134 system in my 94 Dodge works fantastic, blows super cold in all conditions and the entire system is still the original componants on the truck as it came with from the factory. I do have to add a can of 134 about once a season now though but for a system this old not bad.

If I can get my Bronco system to work as well as the one on my Dodge with the 134 I will be a happy camper.
 

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Discussion Starter #8
Check out my A/C Rebuild thread here.
http://www.fullsizebronco.com/forum/showthread.php?t=200136

I replaced every component of my system. I still have 2 pieces left though, the High and low Switch and the respective pigtails.

I beleive the 92 system uses the same components other than the hose. Im pretty sure the hose is slightly different. Pressure sensors probly are as well.
The difference is, you have to flush the piss out of it to get every drop of the R-12 oil out of it as its not compatible with the 134a.
I would just replace everything. Its easy, and you know it will be 100% correct. My A/C just about blows snow out the vents now.
One thing I just noticed was that your build was for a '94 model Bronco, until now that just sort of went over my head for some reason. Was your system 134a from the factory?
 

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The condenser is different between the R12 and R134a systems. Factory R134a systems use a physically larger condenser as well as construction. Everything else is pretty much the same. Factory R134a systems use a high pressure cut-off switch whereas a R12 system does not. Depending on the condition of the hoses I would seriously consider a R12 equivalent replacement refrigerant versus a R-134a conversion based on your criteria of long term ownership.
Aren't the O-rings made of a different material and come in a different color. Green I believe. Is the high pressure switch an actual switch or a sensor? And, how does it work to control the high pressure of a r134 system?

Am I correct that your BKO came with R12? If so, did you upgrade to a post-92hose with the high pressure switch? And, since earlier models don't have a wiring harness for the high pressure sw, how did you wire it up?:whiteflag
 

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This is where my biggest question is does anybody know if the underhood box that holds the evaporator changed or if the later evaporator will fit in the 92 box?
Im not sure if it is different or not, but looking at some pictures on here, it might be possible to pull the box out of an f150 and stick it right in your truck.

1994 was the first year of 134a on the Bronco I believe, so yes mine came from the factory that way.
When I was shopping for the truck I had several things I HAD to have....
94-95 years ONLY.
5.0 L with Mass Air
r-134a A/C
No Rust
New Tires
EB Edition
Leather and Interior in Very Good condition
Little or no engine and transmission problems

I got my wish for the most part. I must have looked at 30 Bronco's before I found this one. It had everything I was looking for. I didnt know about the transmission problems till I got it home. I probably still would have bought it if I knew, just would have beat him down on price a little more. I ended up paying about $4000 or so for it with tax and everything.

It was a good buy around here. I know other parts of the country you could have found one like this for 2000 but not in Flawda.
 

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Aren't the O-rings made of a different material and come in a different color. Green I believe.

Yes - 134a O-Rings are green.

Is the high pressure switch an actual switch or a sensor? And, how does it work to control the high pressure of a r134 system?


Im trying to figure the same thing out myself. Im having a problem with the compressor not cycling at all. It just runs till it freezes up. My old hose looked like the relief valve was blown, and I dont want this to happen again. If the HP Switch/Sensor was bad, it might have caused this, but I need to know more about how the 2 switches work on this system.
 

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Discussion Starter #13
Aren't the O-rings made of a different material and come in a different color. Green I believe.

Yes - 134a O-Rings are green.

Is the high pressure switch an actual switch or a sensor? And, how does it work to control the high pressure of a r134 system?


Im trying to figure the same thing out myself. Im having a problem with the compressor not cycling at all. It just runs till it freezes up. My old hose looked like the relief valve was blown, and I dont want this to happen again. If the HP Switch/Sensor was bad, it might have caused this, but I need to know more about how the 2 switches work on this system.
Okay I may be off base here but I do not believe the systems on these trucks was available with an "automatic temp" control like found on the higher end luxury cars that cut the system on and off. Those controls though are not to safe guard the system but to regulate the interior comfort for the passengers and operator.

Another question is the freeze up occurring when using the max a/c setting? Perhaps try using the normal setting on somewhat cooler days and the system will draw outside air instead of recirculating the colder inside air.


The systems on the Bronco's is a manual system and the switches or sensors actually only work as pressure safeguards both on the low end to ensure adequate oil flow to the compressor and the high end to prevent a dangerous situation that could cause a part to blow from the pressure.

A correctly fully charged system will run all the time when it is turned on, generally there should be enough underhood heat generation from the engine and exhaust manifolds that freezing of the system really should not be a problem.

If I remember correctly from your build the original orifice tube was pretty gunked up and blocked and that probably caused excessive high side pressures which tripped the high pressure cut out.
 

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Okay I may be off base here but I do not believe the systems on these trucks was available with an "automatic temp" control like found on the higher end luxury cars that cut the system on and off. Those controls though are not to safe guard the system but to regulate the interior comfort for the passengers and operator.

Another question is the freeze up occurring when using the max a/c setting? Perhaps try using the normal setting on somewhat cooler days and the system will draw outside air instead of recirculating the colder inside air.


The systems on the Bronco's is a manual system and the switches or sensors actually only work as pressure safeguards both on the low end to ensure adequate oil flow to the compressor and the high end to prevent a dangerous situation that could cause a part to blow from the pressure.

A correctly fully charged system will run all the time when it is turned on, generally there should be enough underhood heat generation from the engine and exhaust manifolds that freezing of the system really should not be a problem.

If I remember correctly from your build the original orifice tube was pretty gunked up and blocked and that probably caused excessive high side pressures which tripped the high pressure cut out.

No there is no Automatic Temp Control on a Bronco, wish there was.
Looks like the Low pressure switch cuts the compressor off below 40 psi and the high pressure switch cuts it off above 400 psi. I will have to look at broncolinks.com and see if I can find where these switches wire to.

My old orifice tube was VERY clogged. Also the evaporator was very clogged. it had only about40% of the surface area able to pass air thru it. I probably blew out 2 cups of leaves and dirt inside the evaporator compartment.
When we charged the system, we found the low pressure switch pigtail had a short. If you moved it around the compressor would kick off. I found in another post where apparently you can change the high and low switch without draining the system. This is a really good thing. I thought you could because I remember seeing a Schroeder valve on the dryer port and on the hose port for the switches.

My other problems are vacuum related. My White vacuum line is badly corroded and could be leaking. Also, when I replaced the heater core, the cable for the blend door popped off and I have not been successful in getting it back on there. So im taking a trip to the junk yard next week. Theres an F-150 there with the dash pulled. Im going to see what condition the vacuum lines are in. If they are good I might snag them and all the vacuum valves. If not, I will just buy some new vacuum valves. They are pretty cheap.

I will have to pull the dash to change them, but I have several issues I need to pull the dash for anyway, it will give me the opportunity to fix it all at once. Sure would be nice to find a donor Dash somewhere too, parts of mine are cracked. I might have to have a look at a few yards this week to see if I can find one.
 

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R12 to 134?

I have done 2 conversions
1) My compressor siezed up. So I took a chance that no bad stuff went into the system. Used the o-ring and fitting kit and just put in the 134. Much to my surprise it worked just fine and in spite of the dire predictions that I would have inferior cooling - that did not happen
2) Another R12 system quit because it was low on R12. Turned out to be a bad fitting so I cobbled up a new end for the bad fitting at the compressor and had the new fitting TIG welded. Put the thing together added lube and Redtek 12. Same result worked fine with no reduction in cooling. Made me happy. Did not change the o-rings or fittings for R12, Cheap.
Redtek is a freon subsitute that you buy at the farm store or on the Internet. Its some kind of green hydrocarbon stuff. Farmers do not use 134 but do use the subsitute.
PaulW
 

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Excerpt from Fordinstallersupport.com AC Manual...

R-134a and R-12 Material Differences (Cont'd.)
CONDENSER
R-134a condensers have more fins per inch and more tubes than most of the condensers used on R-12
vehicles. The changes made to the condenser allow the R-134a system to reduce condensing temperatures,
yet maintain equal or better performance levels as R-12 systems.
FIXED ORIFICE TUBE
From a design standpoint, there is no change to the fixed orifice tube for 1994 and after R-134 vehicles except
for the use of the new O-rings. However, it’s important to note that some R-134a model vehicles may use orifice
tubes that are a different size than the same prior model vehicles with R-12 systems. As orifice tubes are color
coded to indicate sizes, make sure you refer to the orifice tube application chart located in the service tips
portion of the catalog.
LOW PRESSURE SWITCHES
The threads on the clutch cycling pressure switch fitting have been changed to metric. This change was made
to avoid the connection of an R-12 clutch cycling pressure switch to an R-134a system. Some R134a CCOT
systems no longer use A/C Cycling switches, instead using an Evaporator Discharge Air temperature sensor to
cycle the compressor and prevent evaporator core freeze up. These systems may also use a Low Charge
Protection Switch to protect the A/C compressor against low refrigerant charges. TXV systems may use a
thermostatic switch, low charge protection switch, and/or evaporator discharge air temperature sensor.
HIGH PRESSURE SWITCHES
New types of refrigerant containment devices have been added to R-134a refrigerant systems. These devices
include the refrigerant containment switch (RCS), dual function Pressure switch (DFPS), and the A/C pressure
transducer (ACP). These devices are included to disable the A/C compressor before excessive refrigerant
pressures are reached.
SUCTION ACCUMULATOR/RECEIVER-DRIER
A change in desiccant material was necessary for R134a refrigerant systems. Replacement suction
accumulators and receiver-driers use a desiccant material that is compatible with both R12 and R134a
refrigerant systems.
EVAPORATOR
No major changes have been made to evaporator core for R134a systems.

REFRIGERANT HOSES
New refrigerant hoses provide improved containment of R-134a. The main difference between the new R-134a
hoses and most of the hoses used on past R-12 systems is the nylon barrier that improves refrigerant
containment within the hose.
CHARGE PORTS
To avoid using R-12 special service equipment on R-134a systems, the R-134a system employs new high and
low service charge ports. The new charge ports are designed to prevent the connection of R-12 service hoses
and allow only for the connection of R-134a quick-connect fittings that are used on R-134a service hoses. The
unique design eliminates the possibility of using R-12 equipment on an R-134a system. The charge port caps
must be replaced after servicing to aid in refrigerant system sealing.
 

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Discussion Starter #17
jowens, interesting and informative information that you posted. I see that they have indeed incorporated a temperature sensing switch on some systems to combat the problem you have been experiencing.

I wonder exactly where they are installing the sensor? I guess that best bet would be to try to source an A/C wiring diagram that would show exactly how these systems are wired.

Appreciate the information concerning the evaporator, guess I will have to do some research and as long as the evaporator connection fittings to the newer hoses is the same then I could still use the earlier evaporator with no loss of performance. Worse case would be have a shop that makes up A/C lines to change the hose fittings to match up to the older model evaporator.

I still wonder in your case if running the system in normal mode versus Max mode untill you can figure out the newer sensors would perhaps help aleviate your freezing up problems as you would still be drawing in the warmer outside air over the evaporator rather than the colder reculated interior air.

Guess that dealing with a system that is to cold beats the alternative of a system that will not cool adequately though.
 

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Im pretty sure its all in the LP/HP switches. Im going to browse the local junk yards this week. Theres a yard near here that has tons of 90's f-150's. I should be able to find a decent hp and LP switch and pigtail there. Might just take the whole harness if it looks better than mine.

I also have issues under the dash that could be contributing, so im holding final judgement till that is fixed as well. Im going to rip the dash out soon and take apart all the system and clean it if I can do it without destroying it. I also want to replace the foam connections at the vents as well. all my foam is rotted.
 

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Aren't the O-rings made of a different material and come in a different color. Green I believe. Is the high pressure switch an actual switch or a sensor? And, how does it work to control the high pressure of a r134 system?

Am I correct that your BKO came with R12? If so, did you upgrade to a post-92hose with the high pressure switch? And, since earlier models don't have a wiring harness for the high pressure sw, how did you wire it up?:whiteflag
Yes the o-rings are different, I was pointing out the biggest difference between the R12 and R134a system is the condenser. The hoses are barrier type and the o-rings as mentioned previously. R134 molecules are smaller than R12, hence the need to have better hoses to keep them inside the system.

The High Pressure switch is an actual switch that opens the power circuit to the compressor clutch. It is wired in series with the clutch cycling/low pressure switch.

If you are asking me if MY Bronco came from the factory with R12 the answer is no. My F350 is a factory R12 truck.:haha

I am not a fan of R-134 conversions, so I use R146a. It's a drop in replacement for R12. The pressures are very similar between R12 and R146a, no need to install a high pressure cut-off switch. If I were to re-do a R12 system today I would use Freeze12 or one of the more readily available replacements. I had a bunch of the R146a leftover from a project I did about 8 years ago.

Whenever I have a hose that I suspect is leaking I take them to a shop that makes custom hoses. They can put barrier type hoses on my existing fittings.
 

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Seriously, go spend $30 a Walmart, blow the charge, add 134a with oil mixed in. It's a car, not your house. I see no point wasting hundreds of dollars on driers and hoses and coils. All this "do it right" A/C talk is usually from people with little to no A/C experience. I've changed many R-12 systems in the parking lot at Wally World and never had any issues. Do what you want, but that's just my 2cents.
 
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