brake lights out

[ComancheBSJ90]

I thought it was the switch but after testing the new and old switch they both tested continuous with closed circuit. ---Sorry I'm a little hammed---

I get 11.75volts with ignition ON at switch wires.

 

I traced the large wire bundle out through fire wall, from the cab, to front drivers head light. Noticed slight coolant leak through new radiator on side where wire bundle goes to head light. Had a brain wave about in certain conditions that radiator could act like an electric cell and corrode itself as a by product... due to electrical short. Researched the net... no results.

Put negative end of volt meter to radiator and positive to any ground point in engine compartment and I get 0.23 VOLTS, ignition ON or OFF.

 

My Instrument panel fuse blows out on high engine load, loosing dash lights.

 

I had a theory that that wire bundle is grounding out as it traverses the front of truck, but then would not I need put the positive lead of voltmeter to rad and neg to block to get positive reading?

 

Hammered... I mean confused. Any suggesting would be great as I'm off tomorrow and would love to get this figured out.

 

thanks

[vaquaro]

This may not be the same .....re: wire bundle ....But recently went thru simular " no brake lites " , While replacing the b/l switch , I noticed alot of play in the actuator rod bushing ( the new switch didn't cure the no-brake lite problem ) so I wrapped the insert (metal) with teflon tape until the plastic bushing was a snug fit .....Brake lites work fine now :thumbsup: ...New bushing ordered & I guess I have another un-needed part (b/l switch ) in my toolbox :dunce:

[BLHTAZ]

These trucks are well know for bad ground issues. Be sure to trace the ground wires for the tail lights and check/clean the connection points good.

[Eagle]

The title of your post says no "brake" lights. Why are you fooling around up front if the problem is at the rear?

 

Check -- in oder:

 

1. Burned out bulbs (it happens)

 

2. Corroded sockets

 

3. See if you have 12 volts TO the rear lights.

 

4. Bad ground at rear harness.

[ComancheBSJ90]

The title of your post says no "brake" lights. Why are you fooling around up front if the problem is at the rear?

 

Check -- in oder:

 

1. Burned out bulbs (it happens)

 

2. Corroded sockets

 

3. See if you have 12 volts TO the rear lights.

 

4. Bad ground at rear harness.

 

Alright, I admit I was heading north, so took your advise and moved south.

 

I cleaned all the bulb sockets and redid the ground point with no change. I noticed the fuse panel had DOT 3 oil contaminating the fuse connections, and sprayed it out real good. Put in the 15Amp tail light fuse and instant success.

 

I believe it was the combined cleaning that made this work.

 

Thanks for all the suggestions, that was great.

[Eagle]

That means your clutch master cylinder is leaking, and that DOT 3 is extremely destructive. It WILL ruin the fuse panel if you don't get it corrected ASAP.

[ComancheBSJ90]

Dammit,

 

but thanks for the heads up