1990 XLT 5.8 auto- On my way back from Florida to Colorado, all of the sudden the heater (ac/heater) has no power, then I notice that the turn signals don't work either. I checked the fuses, they were goo but I replaced them anyway. The fuses in question are the 30 amp for the ac/heat, and the 15 amp that goes to the turn signals/backup lamps/rear defroster/od on off switch. None of this stuff works now. I removed the fusebox and noticed that the two fuse holders for these fuses seem to share a common wire, if I recall it was a thick brown or grey one with a yellow stripe. Do you think this is the hot for these, or even better, the ground? I really do not want to disassemble the dash and cut all the wires apart to try and trace this. Does anybody have any suggestions?
I really need to fix this, I have no heat in Colorado, and no turn signals.

 

Have to tried using a test light on both sides of the fuse to check for power ?

This is where you start.


Dennis

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I will do that - I won't have time until Saturday. I have to return to work tomorrow. I was on the road with no test light when it happened. It was a long, cold drive home! I do have a fundamental knowledge of auto wiring and I do understand the procedure for tracing these things down. Wwhat I really do not want to do is rip the dash apart and cut all the wiring up if
I don't have to. Let's say for the sake of argument that I find that the common wire for the two fuse holders has no power. I have a feeling that this will be the case, otherwise why would two, and only two, unrelated fuses not be working? Does it have to be repaired to its source, or can I just run power to it from somewhere else? And if anyone else has had this happen, please share your experiences. Thanks

 

j,
on our 96, the power distr. box fuse #15 (50 amps.) is in-line to the heater/ac blower fuse in the cab (#1) and the r/w defroster and turn signal fuse (7).
Maybe someone else who has a '90 can confirm this is the same for that yr.

 

I'm not sure what you mean by "in line," but they share one of the wires that goes to the fuse box. In other words, there are two fuses there that are affected by my problem, and they have a total of three wires. One of the terminal spades for the two fuses is shared. So I am thinking that it may be the wire that goes to the shared spade terminal. If it is bad, can I just run any hot line to it? Or does it have to be the same line? As I said, I have a fundamental knowledege of troubleshooting this stuff, but i am not an expert and don't want to fry the truck.

 

Yes One Power SUPPLY wire should look after two circuits through a metal power Bar.

You will probably have to check behind the fuse box for this.

Dennis

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Yes - it's like you say. I had already pulled the fusebox and saw this. Would this one wire be the power SUPPLY, as opposed to being the power going back to the accessories? If it is the supply, then couldn't I just run any power lead to it if it has no power, rather than trying to trace it and find a break etc.? As long as I use a suitable guage wire, could this cause problems? Also, where would be the best place to get a power supply that is controlled by the key, instead of just taking one off of the battery?

One more thing - does anyone know if there is a place where a wire like this might commonly fail, like a fusible link or maybe one of those many connectors that are located under the hood on the driver's side wheelwell?

 

[updated:LAST EDITED ON 02-Jan-03 AT 02:20 PM (EST)]yo J,

..."the power distr. box fuse ..." - (PDB) is under hood, driver's side, between air filter box and master brake cylinder...
It looks like this (Thanks to Ken for his outstanding site!):
http://froggmann.3iii.net/Tech/ABS.htm

..."in-line".. - Battery power goes to this Power Distribution Box fuse then on to the in-cab fuse in the fuse box.

I went through Haynes and see that the fuses (number) are changed iaw with my 96 Bronco's Power Distr. Box and in-cab fuse block.

Update...see below on the Ignition Switch!

 

I did not see any power distribution fuse box on my 1990. That was the first thing I looked for, as sometimes a fuse blows there and I have seen these on other vehicles. There are just a whole bunch of connectors mounted on the top of the wheel well, where you say the box would be. They are not marked or anything, nor can I just pull fuses from them to see if any are blown.

 

Just looked at Haynes again (an older edition) and see that another possibility other than a short ckt. or open in the PDB/Fuse Block/Harness, etc. is the ignition switch. Nice, huh?
I can't trace the directional signal ckt in the Haynes to confirm commonality to the ign. switch.
As Dennis advised, ck for power to the fuse block for the 2 fuses. Try the test in "Run" key sw. position (w/out eng. running) as well as with engne running.

 

Follow-Up Info


OK, I tested the power lead to those fuses, and sure enough, there was no power. Then, I took a jumper and went from one of the "empty" spades on the fusebox that was hot, and jumped it to where the no power wire went, and bingo! everything worked again. So what I did was to cut the wire that was bad, I left it attached to the fusebox, and connected the other end where I cut it to the hot empty spade on the back of the fusebox. Like a jumper, in other words. Everything is working now. My question now is, it is ok to leave it like this? I believe that the empty spade also connects to a 15 amp speed control fuse. Everything is still protected by a fuse, as far as I can tell, by doing this.