T/L CTSY fuse keeps blowing

[ONEARMEDBANDITT]

I had a radio put in my 1987 c10 and after the install it blew my T/L CTSY fuse I put a 25 amp fuse in it and it keeps blowing the second I turn on my lights. I have head lights just no tail lights or dash lights. Any help is much appreciated

 

[HotRodPC]

You've got a dead short somewhere. Try to eliminate some of the things on that circuit and help narrow down where to look for the short. For example, unplug your harness to the taillights. Replace the fuse, turn the headlights on and see if it still blows. If so, then you know it's not the taillights. If it doesn't blow, then you know the problem is at the taillights.

IIRC, the taillights, side marker lights, dash lights and dome light operate off that fuse.

 

[ONEARMEDBANDITT]

You've got a dead short somewhere. Try to eliminate some of the things on that circuit and help narrow down where to look for the short. For example, unplug your harness to the taillights. Replace the fuse, turn the headlights on and see if it still blows. If so, then you know it's not the taillights. If it doesn't blow, then you know the problem is at the taillights.

IIRC, the taillights, side marker lights, dash lights and dome light operate off that fuse.

Do you know which harness is to the tail lights and dash lights I'll start with those tomorrow

 

[HotRodPC]

I think you can unlplug the taillights near the back of the truck. I'd start at the back, easily locate that harness and work towards the fusebox looking for a plug. I recently worked on a GMT400 truck with taillight issues, so it's possible I'm confusing the 2 different models. Hopefully someone else can step in and confirm for us.

 

[Georgeb]

I think you can unlplug the taillights near the back of the truck. I'd start at the back, easily locate that harness and work towards the fusebox looking for a plug. I recently worked on a GMT400 truck with taillight issues, so it's possible I'm confusing the 2 different models. Hopefully someone else can step in and confirm for us.

This is corect. There is a round 4 wire plug in the rear crossmember. A recent radio install has me thinking they tapped into the instrument lamp circuit thinking it was a ground. Perhaps the light for the climate control. Just a thought because I have seen it before. Otherwise you need to go by process of elimination starting in the back and working up the line.

 

[HotRodPC]

I agree with George. Start at the back and work forward. Not only because it's the easiest way to start, but because the problem is more likely to be back there.

I'll also suggest, I've seen this problem several times before and the problem ended up being in the trailer lighting pigtail grounding out. So if you have a trailer light plug, check those wires closely too.

 

[ONEARMEDBANDITT]

I agree with George. Start at the back and work forward. Not only because it's the easiest way to start, but because the problem is more likely to be back there.

I'll also suggest, I've seen this problem several times before and the problem ended up being in the trailer lighting pigtail grounding out. So if you have a trailer light plug, check those wires closely too.

I think I'm gonna check wires they hooked my radio up to because before they put it in I had zero issues and it's not going back to them bc obviously something wasn't done correct lol

 

[HotRodPC]

For sure. If you recently had a system installed, then the problem occured shortly after, that would make perfect sense.

 

[jetman]

If you have a short that is blowing fuses, the easiest/cheapest way to troubleshoot is to stop blowing fuses. Place an old car horn, using a wire harness w/ male spade connectors in place of the fuse. (stuff rags in horn to save hearing)
Move things around on the suspect wiring till fixed. Just listen to the horn, it will tell you what is going on..

 

[smoothandlow84]

If you have a short that is blowing fuses, the easiest/cheapest way to troubleshoot is to stop blowing fuses. Place an old car horn, using a wire harness w/ male spade connectors in place of the fuse. (stuff rags in horn to save hearing)
Move things around on the suspect wiring till fixed. Just listen to the horn, it will tell you what is going on..

Now that's a great idea !

 

[ONEARMEDBANDITT]

If I'm not getting any power to the dash lights fuse what would be the next thing to check