Blowing dash and tail light fuses

[macdodd]

Hummm,,,,when it rains,,,it pours,,,LOL. As long as I don't pull on the headlight switch,,,,all my lights work,,,stop lights, left and right turn. But the minute I pull the switch,,,it slowly melts the fuse. The headlights stay on,,turn signals work,,,but no dash/ tailights or brake lights. Any suggestions?

[franken]

Figure out which fuse, get a wiring diagram from the electrical section, and start looking for trouble.

[macdodd]

I have a schametic of the wiring for that year truck I bought. I'm gonna order a new switch as I'm sure its the original one in it,,,,like I said,,,luckily as long as you don't pull out the knob, as to turn on the head and running lights,,,,theres no problem. So I can drive it during the day. Thanks for your input,,,,Bill

[macdodd]

Its the tailight/dash fuse that keeps blowing,,,,,

[Jurassic-1]

I would start by unplugging the tail lamp harness in the cab. If it does not blow then reconnect and disconnect at rear frame. It is likely there is a pinched wire under the truck. I always try the easier things first then you could check under the dash and the headlamp switch. Good luck

[macdodd]

Morning,,,,,where exactly is the plug at in the cab,,,,also at the rear of the truck. I'm not familiar with their locations,,,,I'm going to replace the on/off switch in the dash too. I know I sound dumb about the locations,,,,but I've only had the truck since the first of the year,,,,no problems otherwise. Thanks for your input,,,,,Bill

[BMERDOC]

I think Jurrasic-1 may have had a typo. If you disconnect the rear harness at the cab (just above the gas pedal) and the fuse doesn't blow then reconnect it and disconnect the same harness on the rear crossmember and see if it blows the fuse. If it does blow check for wire insulation damage that would be causing a short to ground at the rear harness. Many of these trucks had/have cheap trailer light harnesses and may have multiple damage points.

[macdodd]

Ok,,,,well I went out to pull the switch and found it to be loose, when resprayed the dash,,,I put it in,,,,but,,apparently didn't tighten it down. DUDDDDD,,,,operator error. So far everything works well,,,we'll see,,,,again, thanks for all input,,,,Bill

[Jurassic-1]

Nice, It is always a good day when you get the problem solved .

[macdodd]

Oppps,,,,that didn't do it,,,,LOL,,,,,but found that when I put a new fuse in,,,,turn everything on,,,it holds,,,,,except when I go to the rear of the truck and bounce it up and down,,,,poooof,,,,it blows it. It was on a rack the other day,,,must have moved something. Now to find it,,,,LOL. Do you know the wires run?,,,along the side on the frame on one side,,,then split in the back?

[BMERDOC]

The harness runs inside the driver's frame rail and to the rear crossmember then to the back and right side.

[macdodd]

Cool,,,,yea,,,just checked the LMC book,,,it shows a line going from up under the dash,like you said, down the left side to the rear,,,it shows it then plugs into another line which goes across the back,,,runs the two tailights. If I can,,,I'll unplug the one across the rear,,,put a new fuse in,,,and try it,,,if not,,,then its in the line running from the dash plug to the cross-over line.

[Jurassic-1]

You may want to check it at the frame clips also. It is easily traced down the frame . Also check for burns from the exhaust. It should not be near it but there is always the possibility.

[macdodd]

Yea,,,I'll do that when I jack it up,,,,I'll jack up the left side, put jackstands under it and go from there,,,,

[macdodd]

Whats the best thermostat,,,temp wise , to put in a 350 engine? I'm gonna dump the anti-freeze thats in there and put new in,,,simply because I have no idea how old it is. Took it out for a run yesterday,,,,temp outside was around 97, heat index 107. Temp gauge said it went up to around 210,,that was running at 65mph. When slowing down,,,so did the temp.,,,,thanks for the input,,,,Bill

[7tee]

Originally Posted by macdodd

Whats the best thermostat,,,temp wise , to put in a 350 engine? I'm gonna dump the anti-freeze thats in there and put new in,,,simply because I have no idea how old it is. Took it out for a run yesterday,,,,temp outside was around 97, heat index 107. Temp gauge said it went up to around 210,,that was running at 65mph. When slowing down,,,so did the temp.,,,,thanks for the input,,,,Bill

My 350 has 180* thermostat and also a shroud, all's good...

[MARKDTN]

Originally Posted by macdodd

Whats the best thermostat,,,temp wise , to put in a 350 engine? I'm gonna dump the anti-freeze thats in there and put new in,,,simply because I have no idea how old it is. Took it out for a run yesterday,,,,temp outside was around 97, heat index 107. Temp gauge said it went up to around 210,,that was running at 65mph. When slowing down,,,so did the temp.,,,,thanks for the input,,,,Bill

GM does not sell the 180 any more. They force you to a 195. This is not all bad. I used to be very worried about temps past 180, but to a point the hotter it is the more efficient it is. Now hotter causes other issues like fuel boiling, but that's a different topic. If you want a 180 search out a Robertshaw brand. Think AutoZone still carries them. I have had bad luck with cheap house brand T-stats.

[macdodd]

Cool,,,,,thanks,,,,

[macdodd]

NAPA sells the 180,,,,will check there....

[macdodd]

Question,,,,ref. the tailight/brake/dash fuse blowing. When the line from the back comes up to the front( left side),,,where does it come up into the cab/dash area? Does it go under the kickplate, then down and out to the frame rail? Still is doing the same thing,,,everything holds as long as I don't bounce the rear of the truck,,,wonder if it would be worth my while to just put in a new line?

[macdodd]

Update on the light situation,,,,I jacked up the rear on the leftside. Traced the wiring where I could. When I jacked it up,,,,I jacked up trailing arm so that the wheel went up too. No blow,,,,let it down and pooof,,, now it won't even hold at all,,,sooooo,,,,I order a new headlight switch,,do that first,,,then go from there,,,next I'll order the harness from the switch back to the rear end,,if I can't find the problem,,,jeeeeez,,,,,its the orignal wiring,

[chevytruckluver]

Originally Posted by macdodd

Update on the light situation,,,,I jacked up the rear on the leftside. Traced the wiring where I could. When I jacked it up,,,,I jacked up trailing arm so that the wheel went up too. No blow,,,,let it down and pooof,,, now it won't even hold at all,,,sooooo,,,,I order a new headlight switch,,do that first,,,then go from there,,,next I'll order the harness from the switch back to the rear end,,if I can't find the problem,,,jeeeeez,,,,,its the orignal wiring,

The rear lighting harness should be easy to find along the inside of the left frame rail. You should see brown, yellow and 2 green wires. the brown wire is where you will find your problem. When you pull the light switch out it sends power through the brown wire to the rear marker lights and the rear tail lights. if the wire is nicked or damaged and touches metal it will blow the fuse. By your description of the lights being on and okay until you bounce on the rear of the truck its pretty clear that your problem is in the rear harness at some point. Take some time and inspect the wires carefully. As previously mentioned when people add trailer light harnesses they sometimes can get damaged also causing this same issue.
Good luck

[Userone]

pull your drivers side door sill your dome light wire might be shorting out If I remember reading one of vettevet's posts correctly, that is on the same fuse

[macdodd]

Very cool,,,,thanks alot. When the wires leave the switch on the dash,,,where do they go,,over and along the side where the emergency brake is? If so,,,then where? I'm gonna jack up the whole left side of the truck, put jackstands under it and go from there,,,,I looked today at the wiring,,say from the left-hand rear wheel to where it goes across the rear of the truck,,,didn't see anything,,,but then again,,its the orignal wiring. At least I can drive it during the day,,,brakes work fine as long as you don't pull out the headlight switch,,,LOL. Say,,you might know,,,is there a plug-in that separates the side line from the one across the back? Or was it made in all one line in that year truck?

[macdodd]

I disconnected the rear harness from the line along the left side frame,,,the fuse is holding,,,but I see the dash lights aren't on,,,,I would imagine that maybe the circuit wll be complete when you plug the rear harness in,,,,we'll see,,,,