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85 No eletrical power at all

10391 Views 9 Replies 3 Participants Last post by  Northernguy
Well, I pulled the idiot move the century tonight. My bronco has a weak battery, so I was going to jump it as it sat for a bit. Well it was dark, and I managed to cross the +/- cables. I didnt notice right away as it was dark. I the truck fired, started and then went dead. At this point I still wasnt sure what happened as it was dark, and I didnt see the smoke coming from the battery. I got it unhooked after about 45 seconds , luckly the battery didnt blow. But now I dont have anything. No eletrical what so ever. I know Im an idiot but where should I start looking to fix it? I cant find my chiltons at the moment either. I went and got a spare starter solenoid thinking I might have burned that up, but it didnt work.

Any help (besides calling me stupid, which is well deserved)

The truck is an 85 bronco

I would think I burned at least one (several) fusible links up
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It happens.

Wiring Diagram for 84 Bronco & F-Series; "...Similar to 80-91 Bronco & F-Series..."
Source: by Steve83 (Steve, That dirty old truck) at

Check Fusible Links:connected to the battery side of the starter relay to da Alternator

Ignition Switch (think it's a Yellow wire)

Fusible Link at Ignition Switch and Alternator to Battery Wiring Diagram in an 86
Source: by Xris at
Location pics in an 85 & 89 the first two pics are of an 89 5.0. because of the loom i wasnt able to trace the wires...The second pic is at the starter relay to show you a fusible link wire (the green wire in my fingers you can see at the eyelet there is a black plastic block). the third pic is of my 85. i think that big block is another style fusible link ford used on older stuff (but im not sure)..."
Source: by shift1313 (Matt) at

Hopefully the relay &alt's diodes are still good.
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I was rushing so I didn't ask if you have a multimeter, etc. ahd have you checked batty voltage yet?
Static testing : With a good digital voltmeter check the static voltage. If it is above 12.6 remove the surface charge by operating the headlights for 15 to 30 seconds and then recheck. A reading of 12.6 or higher indicates a full charge. A reading of 12.4 indicates 25% discharge. A reading of 12.2 indicated 50% discharge. A reading of 12.0 indicates 75% discharge. A reading lower that 12 .0 indicates almost complete discharge.

Also, when you can run the engine, verify that no-load voltage is 13.8 - 15.3V @ BATTY

Diode Leakage Test; "...To check alternator diode leakage, connect the multimeter in series with the alternator output terminal when the car is not running. Leakage current should be a couple of milliamps at most; more often, it will be on the order of 0.5 milliamps. Use care when disconnecting the alternator output wire; make sure the battery is disconnected first..."
Source: by ==== I'd pull it and take it to NAPA or an Auto Electric Shop.

You can test the st relay; pull cables and apply 12 v dc to small post with relay metal body as the ground.. se if you have continuity between large terminals.
Try to start it @ relay

Sewiw shows a remote start switch's RED & BLACK insulated Jumpers; you can use a reg. small jumper wire between those 2 terminals to bump the starter

Chilton; many local library's offer free online access for their members; just log-in w/your library Card # and password; incl. all Broncos, & many MAKES! 1951 to 2009; some years (85-96, I believe) include: FULL Technical Service Bulletins and Recalls, Labor Hours per repair (plug in appl info); Wiring Diagrams, Vacuum Diagrams (in DRIVEABILITY AND EMISSIONS CONTROLS Section), Specifications (torques, etc.) & Maintenance Intervals

Repair Guides & Wiring Diagrams (click vehicle, year range) & go to Chassis Electrical & scroll for Wiring Diagrams...(under license from Delmar Publishers, comb of Chilton/Nichols/Delmar & Haynes); some may be incorrect, as reported by Seabronc, thanks Seabronc! NEW SITE URL!!! MUST REGISTER TO VIEW; select year, make, model, engine size and go to appropriate section
Source: by Chilton via Autozone @
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I jumped it with my DD truck. I didn't have my multi meter on the farm, plan going back today with it. I have no lights/horn at all, going to check the ground strap. Ive never blown a fusible link before. You can tell when there burnt right? I looked at the several that were hooked up to the starter solenoid last night, and they all looked normal. Nothing looked charred/melted
It would be nice if they showed damage when they are blown but they do not.
I have a similar problem in my truck.My battery was put in backwards and when the battery cables were placed in position sparks started to fly like crazy.It hurt like hell but managed to remove them.
I have trouble starting my truck at times.I changed a few of the fusable links near the solonoid(also new) and it helped but I still have other wiring issues caused by it.When I turn the key to start I have to wait a second or two for the connection to work.I wish I knew where to keep looking or what else to replace.
Note I am not the dumbass that put the battery in backwards.:goodfinge
I also think that is why my gauges are always pinned to the right.All except fuel.

Figure 21 Most fusible links show a melted, charred insulation when they burn out.
See this & other info @
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I also think that is why my gauges are always pinned to the right.All except fuel.
Instrument Voltage Regulator (IVR) in 78-86; Best indication of a bad IVR is that gauges perform radically at the same time since the constant voltage side of the gauges were receiving wrong or intermittent voltage

Instrument Voltage Regulator (IVR) Location & Causes of Erratic Gauges in 78-86; "...The cluster "voltage regulator" is going bad, and staying on too long, sending too much current through the gauges & sensors. It has finally locked on, and is burning out your sensors every time you turn your key on. :( Remove the instrument cluster and then pop the VR off the film circuit - it's a metal box with 2 brass snaps. They're available at most parts stores for a few bucks. The hardest part will be getting the headlight & wiper knobs off, so post again if you need instructions on that.In this photo, counting from the RIGHT, it's between the 2nd & 3rd black bulb holders along the top of the cluster. You can see the hex screw holding the mounting tab, and just below that, you can see the 2 brass snap terminals..."
Source: by Steve83 (Steve, That dirty old truck) at FSB

Instrument Voltage Regulator (IVR) Pic in 78-86; "... MOTORCRAFT Part # GR513 {D1AF10804AA, D1AZ10804A}..."
Source: by @

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Thank you for the info miesk5!
I have never seen the fusable links look that bad when they went on my truck.Thank you for clearing that up and thanks for the info.
I do feel like I Hi-jacked the thread though.:smilie_slap
Sorry mjs408 but I thought it might help your prob as well!
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yo, YW pal!
Try this temperature gauge/sender test first;
"...If you take that single wire that Seabronc is talking about (that is the sender's wire) and ground it to the block the guage will imediately go to HOT; that will tell you if its the guage or the sender . There is another mounted back farther in the intake and that is for the EEC to determine timing curves and injector pulse time..."
Source: by BLADE262US & Seabronc
Testing; "...Pull the R/Wh wire straight off the sender & ground it to the block, intake, or head. Then turn the key to RUN. If the needle pegs, replace the sender. If not, diagnose the circuit.. by Steve83

The IVR can fail two different ways. it will quit working altogether, thus none of the gauges will work...

Or two, it will stick, and the gauges will peg to the extreme right, then it will unstick and fall back to normal.

The IVR is a pulse type. The voltage is regulated by how fast the pulses are. When it sticks, it doesn't pulse, etc...
Try tapping on it.
Make sure the cluster ground is in good shape. If the IVR isn't grounded or has an intermittant ground, it wont pulse like it should
Locations in an 84; G203 RH side of engine; G208 near TPS; G209 forward of RH side of dash panel; G701 behind IP near LH side of radio; G757 front of engine near distributor
Source: by Seabronc
Locations in an 86 ; G701 Behind IP near RH side of radio; G801 On LH inner fender behind headlights; G802 On RH inner fender behind headlights; G903 At LH side of rear crossmember; G909 at lower LH cowl access hole; G1003 On LH side of frame behind front crossmember; G1006 Rear LH side of frame at rear crossmember; G1303 at LH radiator support
Source: by Seabronc

Suggest getting one from a Yard;
Since there are about 12 different types, make sure to take the old one with you
1971/86 F100/350
1971/91 Econoline
1978/86 Bronco

1977/79 LTD II/Ranchero/Cougar/Thunderbird without Tachometer.
1972/76 Thunderbird/Continental Mark IV
1971/72 LTD/Mercury Marquis

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I lowered my steering column and did a continuity test on my Ignition switch.

I would like to test it exactly the way the Haynes manual says but I can't!lol
The wires are in a different order in the switch then they are in the book.Imagine that! I got some of it figured out but I sure would like to be sure.
My truck is an 81 but the wiring is 80 with a few different colors thrown in for fun.
In the book all the plug areas are filled using 11 wires.Mine has 11 wires but in different spots.I have 3 empty spots on the plug so I am not sure how to do a proper continuity test.

This is how its wired in my Haynes manual.

mjs408 I suggest you check yours out too!lol I also have no computers in my truck to fry.
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