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Discussion Starter #1
My 93 was an R12 a/c system that didnt work when I got it. The front pump seal leaked all the oil and refrigerant out and the pump got trashed due to no lubrication.

I got all the R134 parts swapped in full of PAG oil and charged with freon. But when I turn on the a/c the pump will only engage for about 1 second then disengage for several minutes then engage for 1 second again.

What is the problem here? Could the pressure sensor be bad? I have a working r134 truck and the pressures are the same between the two at rest. I do not have to much refrigerant or oil in the system. Its not running the pump long enough to pull pressure down to think its low on refrigerant.

Thanks for any help I need it bad!
 

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There is a sensor on the accumulator that keeps the compressor from running with no or low Freon. I have seen BKO's that did not have one. If you know you're system; evacuated (pull vacuum with pump) filled with R-134 and you are good to go...do what (not the professional mechanic fix, but it works great) I did...I ran a fused wire from the battery to the dash, where I wired a simple on off switch, back to the compressor. I did it because my dashboard AC control would not fire the compressor. Remember to shut it off when you stop. But it does sound like the switch on the accumulator is preventing the compressor from staying on. Do you have the gauges and a vacuum pump? This is important! I learned from mistakes. If there is a lot of AIR in the system and freon was put in, it might not ever work. Good luck.
 

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Invest in a manifold gauge set, that will tell you exactly what is going on. If the clutch cycle switch was bad typically the compressor will never engage assuming the charge/pressures are in range. Re-reading your post I see you do mention pressure....are you using a manifold gauge set to monitor the low and high side pressures at the same time?
 

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Discussion Starter #4
I dont have a high side gauge but I do have a low side one. When the comp is disengaged it has 80 psi of low side. When I jumper the low side switch the comp comes on and stays on so I think the low side switch is bad. I ordered a new one and it will be here tomorow.

In other news when I jumper it and get the pump running the front a/c unit blows hot air but the rear unit that runs off the same comp blows nice and cold.
 

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what are you working on? cause that aint no bronco! does that thing have 2 condensors and 2 blower motors?
 

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Discussion Starter #7
got er nailed down. The low side switch was bad so changing it out helped. Then with that working correctly made it possible to get it full of freon. Blows nice and ford cold now front and rear. :thumbup
 

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Great news! Thanks for the feedback.
 

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got er nailed down. The low side switch was bad so changing it out helped. Then with that working correctly made it possible to get it full of freon. Blows nice and ford cold now front and rear. :thumbup
Where did you get the switch? Mine stays on for more than a second but not much. maybe 3-5 seconds on then 3-5 seconds off, repeat. It wasn't doing that until today. I attempted to refill it but doesn't seem to be doing anything. The guage that came on the can shows pressure build to about 35 then when the compressor kicks on down to 25, when off builds back up to 35.
 

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Discussion Starter #10
Where did you get the switch? Mine stays on for more than a second but not much. maybe 3-5 seconds on then 3-5 seconds off, repeat. It wasn't doing that until today. I attempted to refill it but doesn't seem to be doing anything. The guage that came on the can shows pressure build to about 35 then when the compressor kicks on down to 25, when off builds back up to 35.
Its is still low on freon. The cut out switch shuts the compressor off at 25 psi then re-engages the compressor at 35. So add one more can and see how it does then. It should run at about 35 psi as the lowest when all is working right.


My bad switch was cutting the compressor out with 50 psi and back on at 75 psi.
 

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its the fuller full size bronco and yes two condensors and two blower motors like a van

sorry i blew up. Nice Rig:thumbup:beer
 

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I broke down and bought the manifold guage set to measure low side and high side and it will enable me to use that to refill it too. Based on the readings it does just appear to be low still but the crappy guage that came with the fill can I initially bought sucked. I bought a plan old can without the trigger and will use the manifold thing to refill when I get a chance.
 
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