Electrical issues help needed

[patrick1151]

Bare with me as my knowledge of electrical is mostly limited to turning lights on and off. I appear to have a serious short as no matter what size fuse I put in my fuse box for the taillights/rear defogger/gauges/dash lights spot it blows. Ok yeah the idle stop solenoid is on that circuit as well meaning the car isnt running that great. Also meaning I have none of the above and cannot drive my wagon at night. ARGHHHH. Seeing how with one of my employers my shifts start at 6am meaning I leave home at 5 I have a problem.

Ok, I suspect the short is in the wiring to the rear defogger as it never worked well and the other day when this majorly flared up I breifly had some blue smoke come out of where the wiring for the rear defogger comes out of the headliner at the rear of the car. I dont currently have a test light which is part of my problem. Anyways I tore my dash apart to disconnect the relay hoping to kill power to the defogger but I am still blowing the fuse. There are 3 wires going to the rear defogger, 1 purple,1 brown and 1 black. Only the purple one goes through the relay. I am guessing the black is a ground. I am friggin tempted to cut the wires behind the A pillar trim and kill them seeing how the defogger never worked well anyways but I want to make sure that will solve the issue.

Suggestions please.

[cjbiagi]

I have seen the wires deteriorate going to the rear defroster in exactly the area you described. You can remove the metal cover by the rear of the headliner where the wires come out and see what they look like. Isn't the defogger on its' own fuse? That thing draws a lot of current, I thought it was by itself and not tied in with any other circuits?

[patrick1151]

it isnt amazingly enough, the circuit is simply marked tail lights but everything else goes out when the fuse does. I have that cover off right now and thats how I saw the blue smoke. Interestingly enough I also lost my signal lights this weekend but simply changing their not blown fuse with a good one solved that. I do have brake lights which is a different circuit. If the short was in the rear taillights, wouldnt the brakes lights be affected as well? I guess I could see if I could kill the power somewhere to the taillights and see what that does. I did put a tester light across the fuse for the taillights and it did light up.

There is no fuse in my fuse box labelled rear defogger either.

[spencerforhire]

Unfortunately the Monza/Sunbird wiring diagram does not show a rear defrost, but it should not be on the tailight fuse anyway. The rear defrost circuit should have a timer relay in it somewhere that you could disconnect to isolate it from the rest of the wiring.
For clarification, the taillights and brake lights are on 2 separate fuses, both work without the key, and the signal lights are on another fuse fed only when the ignition is on.

[marco_1978_spyder]

There's that breaker thing on the firewall, It's a little square thing mounted above the fuse block.

It has 2 terminals. I know disconnecting this eliminates the rear defroster, maybe other things too. Might want to poke around there, or see if the short is somewhere around there? Just a shot in the dark.

[Len]

Hi all , I do believe Shannon is referring to his Safari wagon and not the sunbird.
But dang if I can remember the year .
Len

[patrick1151]

It is my 77 Astre wagon thats the problem. Maybe the rear defogger isnt the problem then . But I know when that fuse blows, I lose it as well as the taillights and all. I hae unplugged the harness to the relay but there is a second wire that I think is a power wire that does not go through the relay. my relay has only the one 4 wire harness and a ground wire on it.

Shouldnt the blue smoke indicate the bad spot or could I have made things worse by running to high of a rated fuse?

[cjbiagi]

Haven't you heard the old saying "put a bigger fuse in and look for the smoke"? Seriously, the smoke is a obvious culprit. You may have more than one problem though.

[patrick1151]

thats why I blamed the defogger and was trying to kill power to it. I guess I will just cut the wires behind the A pillar trim and wrap them up and see what happens. I can live without the rear defogger long term but not the rest.

Part of the problem now is that no matter what size fuse I put in there it blows immediately. On what hopefully will be my parts car for my v6/power brakes/power steering upgrade it has good electrical so if its the rear taillights harness I will just swap it over and make it work.

[patrick1151]

ok well I can conclusively say the main problem isnt the rear defogger. I guess I need to check my taillight wiring next. The only thing is that a new fuse doesnt blow quite as quickly now.

[spencerforhire]

The big question is whether the fuse blows when you stick it in the fuse box or when you turn on the lights. If it blows when you stick it in, the problem is NOT in the taillights. There should be nothing else on that circuit anyway; if this is the case, I suspect some previous owner may have tapped something into the orange wire that feeds the taillights by way of the headlight switch(orange in, brown out). If it doesn't blow until you turn on the lights, it may be as simple as a tail/signal light bulb installed crooked.

[patrick1151]

I blows almost immediately when I turn the key doesnt matter if I turn the car on or not. I didnt change anything bulb wise recently. As for whats on the circuit, all the other stuff stops working as soon as the fuse blows so I figured it was all on that circuit.

[spencerforhire]

Whatever fuse is blowing, it's not the for the taillights; they are not hooked to the key. You must be reading the label on the fuse box wrong.

[patrick1151]

Well its definitely labelled taillights/gauges. And when that fuse blows I lose my dash, taillights, gauges and idle stop solenoid. They were all working previously. At this point I think I will just strip all the wiring out of my parts car and use it all in the wagon when I do the swap. Its a 78 Monza S hatchback which is the same as a 77 Vega. I know the taillights are different but hopefully I can make them work.

[my79monza]

Patrick, As Spencerforhire said the rear window defogger is fed from the circut breaker at the fuse panel.
It (power)comes from the starter thru a fuseable link to the circut breaker (red wire) then on to the relay( Orange wire) then purple back to the window.
Once you unplug the relay the power cannot go further than the harness you unpluged.
I believe you will fing a melted harness by the back window at the source of the smoke and you will have the tailight wire going to ground.
I don't think you need to look any further than the source of the smoke.
Its worth a try anyway.

Merle