Head Scratchin Electrical Issues

[Thewespaul]

So some of yall may have seen some of the electrical gremlins Ive been fighting with the ambulance project but Id like to devote a seperate thread to see what yall may think.

So little background, this is a 1991 f350 cab and chassis that was upfitted by a seperate company with a hefty amount of wiring and electrical work to setup the ambulance parts, we know everything worked several years ago when it was originally inspected and registered, it no longer needs and inspection since it is registered as a military vehicle, but I want to see these issues fixed.

Since then, the column has been replaced and converted to a tilt unit. With the non tilt turn signal switch, turn signals work as they should, but with the tilt signal switch in I get hazards coming on when left turn signal is engaged. Why do yall think this would make a difference? Looking at schematics for this truck with a tilt and non tilt harness I am seeing zero differences in how it is configured, but maybe Im mistaken?

As of now after the truck drove two hours to Austin it has no brake lights now, have not had a chance to confirm if the fuse is blown, but I had that fuse blow earlier in the year but didnt have an issue since then, so Im suspicious of that.

Historically, this truck also had intermittent reverse lights but has zero reverse lights currently. MLPS adjustment didnt fix this and I havent pulled schematics for ahead the MLPS but where would yall think I should be looking next? (aside for looking for a 4x4 zf5)

Any help is appreciated with wrangling these angry pixies!

 

[no mufflers]

Any chance a wire got mixed up on the plug from the column switch to the truck side?

The brakes all go through that plug with the turn signal.

 

[Thewespaul]

Well theres always a chance for my own error, wouldnt be the first. But with it having the same issue carried over with different switches in the column, I sure hope I didnt get it wrong that many times, but definitely something to take a look at

 

[laserjock]

I think you may be fighting multiple issues but the first question is the switch new? Like no mufflers said, all of that goes through the turn signal switch and the tilt and non-tilt are a bit different. I seem to remember on difference being the hazard switch. I don’t have them with me but I think there’s a reason the tilt and non are different besides the tilt mech.

Here are the wire color positions.

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I fought a similar issue with no brake lights. The no reverse lights is interesting. Auto or manual? I’d be tempted to say check your fusible links. You may have a bad one and it’s feeding backwards through the hazard switch causing to act funny. Hazard and brakes are on a separate circuit (link) from most everything else. I finally deleted all my link wires.

 

[chillman88]

I had a similar issue blowing brake lights that was cured when I changed out my steering column. Is it possible you have TWO bad tilt column switches?

 

[no mufflers]

if it were me i would work from the column down and power each wire to see if you can make the lights work one at a time.

really the only thing i can think of to help ya out.

 

[Thewespaul]

Thanks for helpful comments guys, the switch is new and has had three new switches so far connected up to it, the only one that seemed to have no issues was the non tilt switch that was incorrectly packaged as a tilt switch. Under the dash the harness is no where close to factory ford schematic, theres 5 wires coming out of the brake switch iirc, so its pretty challenging tracking issues with all the ambulance wiring in there. The back feeding fusible links is an interesting idea, Im gonna do some research and see what I can dig up there, the truck has an e40d with a banks transcommander. Trans has no issues and shifts great, just no reverse lights. I got word last night the low range 4x4 light is staying on now
These electrical issues...

edit. Looking at some pics from when I repinned the switch harness to run it down the column the wiring looks correct, hmmm

 

[no mufflers]

the 4x4 light, would it be the one that started to melt the plastic in the cluster? maybe an ongoing thing?

 

[Thewespaul]

Could definitely be. Never noticed it being on until last night which is odd, this truck has a ton of parasitic draws, I fixed a couple but I’m sure there’s more

 

[Thewespaul]

Update, fuse was blown for brake lights and now replaced. Overdrive on off is not working and low range 4x4 light is not on.