[Doug_I]

86 Tbird electrical problem some things work some don't (only drive during daylight)

Hello everyone
I bought this car in 1992 with 52,000 miles on it, and just turned 150K it has the 5.0 engine with AOD
Long story short it sat in the driveway for a few months, but started every two weeks or so. Some things work some don't. Re-seated all the fuses in the fuse block which made it possible to start with the key,,,, Re-seated the headlight switch with no change......still have some "minor" glitches..Hoping it's a loose connection somewhere

Question is where to start,,, heading under the car to clean starter and ground...
Just finished checking fusible links OK

DOES WORK...
Fuse 1,2,5,10,14,18

Directionals front and back
Brake lights with cyclops
hazard lights
power windows
Wipers
horn

DOESNT WORK
Fuse 4,6,8,12,13,15,17

Clock
power door locks
Power mirrors
power seats
odometer does not show numbers (digital) but does light up
Headlights high or low beam
dome lights ( center and spots)
driving lights

 

[PSIG]

I don't have a wiring diagram to assist with, but the best general tip I can give is GROUNDS. Poor or intermittent grounds are by far the number-one source of automotive electrical issues. Get your hands on an electrical schematic for your car, and find all the grounds (there are many) and clean 'em up first. Then everything else (fuses and connectors) clean and tight as you'd expect. Good luck!

David

 

[Arabian454]

Re: 86 Tbird electrical problem some things work some don't (only drive during daylig

Question is where to start,,, heading under the car to clean starter and ground...
Just finished checking fusible links OK

DOES WORK...
Fuse 1,2,5,10,14,18

Directionals front and back
Brake lights with cyclops
hazard lights
power windows
Wipers
horn

DOESNT WORK
Fuse 4,6,8,12,13,15,17

Clock
power door locks
Power mirrors
power seats
odometer does not show numbers (digital) but does light up
Headlights high or low beam
dome lights ( center and spots)
driving lights

The fuses that don't work, have you tested them with a test light?
I would test the bad ones with a test light attached to a good ground.
Pull the fuse and test the 2 sockets for fuse in fuse box with test light 1 should have power. I would test all the bad ones.
If they have no power I would think you got bad feed/power wire somewhere.
Does the car have fusible link? Maybe a animal ate through a wire while it was sitting? Corrosion? If you have a wiring schematic look and see where the bad fuses get their power from and start there. Would think problem would be before fuse box.

If the bad fuses have power when you test them then your problems would be after fuse box. A wiring schematic would make it easy.

 

[Doug_I]

fusible links checked out, and tested the fuses with a test light the ones that didn't work mentioned before have no power at the fuse block. The chilton wiring diagram isn't very helpful. they seem to have left out quite a lot. the lighting circuits aren't on the diagram at all.

 

[Arabian454]

fusible links checked out, and tested the fuses with a test light the ones that didn't work mentioned before have no power at the fuse block. The chilton wiring diagram isn't very helpful. they seem to have left out quite a lot. the lighting circuits aren't on the diagram at all.

Without a wiring diagram kind of hard to diagnose. I didn't see any posted online either. If you could scan and send the diagram you have may help if it is big enough to read.

But you need to find where the power comes from to feed the bad fuses. You could remove fuse boxe and look at back to see color of wires that supply the power to the bad ones and backtrack them from there.

Sometimes a bunch (4 or 5) of fuses share the same supply and sometimes only 1 or 2 share supply again you should be able to see this from back of fuse box.

Also the supply could be hot all the time or only hot when key is on. For example the one for your power door locks should be hot all the time so they work with key off or on. Wipers would only be hot when key is on.

Hot all the time the power supply would come from starter relay or sometimes headlight switch. Something that is only hot with key on, power would come from ignition switch.

As for your bad ones, clock, power door locks, and lights, I would think are hot all the time. Power mirrors and power seat could also be hot all the time but not sure.

When you checked your fusible links did you check power on both sides of link, power going in and coming out? Also I would check the connection where the wires pass thru the firewall maybe some corrosion or bad connection there.

The first thing I would do is unbolt fuse box so you can see the back of it. Then test the power/supply wires for your fuses with key on and key off to see which ones are dead and go from there.

If you could scan and send the wiring diagram for your car or find one online I could look at I could be more help. Hope this helps you some.

Lou

 

[Doug_I]

Hi Lou, Here are the diagrams for the 86-88 tbird. The size of the file was to big to post on the thread. The first thing I see is the diagram only shows one wire coming off the battery other than the battery cable itself. My car has fusible links coming off the starter solenoid four coming off the stud that split into 7 fusible links

engine wiring
https://docs.google.com/open?id=0B38bcrGEMDigOWtMOHJ2bFVuWTg

Chassis wiring—1986–88
https://docs.google.com/open?id=0B38bcrGEMDigUTlHaW5Na1VtUHc

Chassis wiring—1986–88 continued
https://docs.google.com/open?id=0B38bcrGEMDigeGN2U3Q4NkZsSjg

 

[Arabian454]

Doug, you are correct the wiring diagrams are missing a lot. Where did you get those?
Yesterday I went to the Ford Dealership I use to work at to see if they had a diagram. They didn't have anything older than 1990.

The diagram you posted didn't have fuse box and they only showed 3 wires on ign switch which is little help.

What you need is something like these. This link shows diagram for fuse box, now this is for 86 truck not your car, just using as example.

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If you look at the bottom 4 fuses in fuse box you can see they all get power from once source. Looks like headlight switch but writing is a little small for these old eyes.

Here is a diagram of a ign switch, look part way down page. This is also just a example and not correct for your car, 90 mustang I think.
Key lock cylinder or ignition switch?? - Page 2 - MustangForums.com

You can see here ther are a few wires that feed the fuse box. They tell you what fuses they feed.

Now since you have a few fuses that have no power and all the fusible links are good I would think you have a problem with the feeds to the fuse box.

I would pull the fuse box loose and look at the back of it to see what color the wires are that feed power to your bad/ dead fuses and see where they go to. Ign switch, headlight switch, etc. One wire could feed multiple fuses as seen in the one diagram. So one or two wires/ connections could solve a lot of your problems.

If you wanted to throw some parts at it instead of taking it all apart and back tracing the and testing the wires I would replace ignition switch and maybe headlight switch, seems they supply many of the fuses with power.

You said you reseated? Bunch of stuff and that helped some. Was that just pulling apart the connector cleaning and reconnecting? Maybe do the ignition switch?

If you do loosen the fuse box, test the feed wires to your bad fuses with a test light, prob no power. Look at the color of those wires and see if same color wires go to ign switch or headlight switch. If they do then test wire coming out of switch for power. If it has power then wire is broke somewhere in between switch and fuse box. If no power then I would replace switch.

Hope this helps ya

Lou

 

[Doug_I]

spent some time on it and concluded all good to firewall, My neighbor who is a mechanic by trade came over and stuck his head in for a look. the high low directional arm on the column was what we found to be a problem. when the arm was pulled back (flash to pass) the battery/voltage light would go out and the fuel pump would run, when released light would come back on and the fuel pump would stop.......now there is some power to ignition but that curcuit is now dead. I took the switch from the column apart cleaned all connections made sure females were tight reassembled with no change

 

[Doug_I]

The diagrams came from Chilton Manual online Sad isn't it

10-15-2012
spent the morning looking for a directional switch that was $75 in the local boneyard, but waiting till the morning for a $50 new one (figure that one out) started testing the ignition switch after the second test the car started 3 times then nothing again....took out and tightened the female connectors in the ignition switch and still nothing