1970 pickup fuse blows when brakes and? - The 1947 - Present Chevrolet & GMC Truck Message Board Network

camaney · 01-19-2015, 10:47 PM

Need some help to figure out where to check first
when headlights are on and press brakes I get a short...
the brake light works good if the headlights are off and vise versa
any ideas? I know they share the same fuse...thanks

**FirstOwner69** · 01-19-2015, 11:55 PM

Just a thought...

Since the taillights are on with the headlights and the taillight and brake light filaments are in the same bulb, you may want to try removing one bulb at a time, turn on the lights and hit the brakes to see what happens.

camaney · 01-20-2015, 12:01 AM

Good idea..thanks

Birza25 · 11-11-2015, 11:16 AM

Quote:

Originally Posted by camaney

Need some help to figure out where to check first
when headlights are on and press brakes I get a short...
the brake light works good if the headlights are off and vise versa
any ideas? I know they share the same fuse...thanks

Hey I'm having the same issue, what did you do to fix it?thanks

**WIDESIDE72** · 11-11-2015, 12:58 PM

I had a mid 80's truck with a similar problem. I'm not sure if it was factory or not but the sockets were full of grease. I assume it was dielectric grease, but it was all dried out and was causing high resistance. It wasn't enough to blow the fuse if the headlights were of but with everything on it would blow the fuse as soon as I touched the brake pedal.

**WorkinLonghorn** · 11-11-2015, 03:52 PM

I just recently went through similar troubles and after about a dozen blown fuses I got it figured out but for me it was very complicated.

It started RIGHT after I finally replaced the broken front right turn light socket so I assumed it was the cause.

Long story made short ( no pun!) it turned out to be a wire chaffing against the rear bumper.But it would only blow a fuse occasionally and thus caused me to scratch my head bald, especially since I have trailer wiring plus camper wiring plus some sort of custom work the original owner did.

46 years of chaffing and it shorted out. I guess they don't make anything to last any more.

I would check the entire system inch by inch.

Andy4639 · 11-11-2015, 04:02 PM

Will it work fine up till you press the brake pedal is what I understand you are saying. So that tells me it's some place between the brake switch and the rear of the truck.
As stated take one rear bulb out and see if it blows the fuse. If not put it back in and take the other side out and try it. If one are the other blows the fuse then look on that side of the wiring.

Medhawk020 · 11-13-2015, 01:23 AM

I had the problem on my 1970 C20. What I did was replace the wiring to the rear lights. There are two wires from the dash to the back.

camaney · 11-13-2015, 04:54 AM

I replaced the headlight switch and that's it..it worked

camaney · 11-13-2015, 04:56 AM

Quote:

Originally Posted by Birza25

Hey I'm having the same issue, what did you do to fix it?thanks

Headlight switch

Birza25 · 11-13-2015, 09:59 AM

Thanks guys! Started going threw some wiring and found my hi/low switch on the floor was completely melted to the floor. Haven't had a chance to check the fuse yet. I checked the dome light wires they all look good. Po had changed the headlight switch. I still need to check the harness and so on.

First c10
1969 shortbox
454/t400/12 bolt

01-19-2015, 10:47 PM	#1
camaney Registered User Join Date: Feb 2008 Location: sacramento california Posts: 204	1970 pickup fuse blows when brakes and? Need some help to figure out where to check first when headlights are on and press brakes I get a short... the brake light works good if the headlights are off and vise versa any ideas? I know they share the same fuse...thanks

01-19-2015, 11:55 PM	#2
FirstOwner69 Senior Member Join Date: May 2010 Location: Wisconsin & Arizona Posts: 4,852	Re: 1970 pickup fuse blows when brakes and? Just a thought... Since the taillights are on with the headlights and the taillight and brake light filaments are in the same bulb, you may want to try removing one bulb at a time, turn on the lights and hit the brakes to see what happens.

01-20-2015, 12:01 AM	#3
camaney Registered User Join Date: Feb 2008 Location: sacramento california Posts: 204	Re: 1970 pickup fuse blows when brakes and? Good idea..thanks

11-11-2015, 12:58 PM	#5
WIDESIDE72 Senior Member Join Date: Aug 2008 Location: Cedar Park, Texas Posts: 7,500	Re: 1970 pickup fuse blows when brakes and? I had a mid 80's truck with a similar problem. I'm not sure if it was factory or not but the sockets were full of grease. I assume it was dielectric grease, but it was all dried out and was causing high resistance. It wasn't enough to blow the fuse if the headlights were of but with everything on it would blow the fuse as soon as I touched the brake pedal.

11-11-2015, 03:52 PM	#6
WorkinLonghorn Senior Member Join Date: Dec 2006 Location: Studio City, Calif. Posts: 2,886	Re: 1970 pickup fuse blows when brakes and? I just recently went through similar troubles and after about a dozen blown fuses I got it figured out but for me it was very complicated. It started RIGHT after I finally replaced the broken front right turn light socket so I assumed it was the cause. Long story made short ( no pun!) it turned out to be a wire chaffing against the rear bumper.But it would only blow a fuse occasionally and thus caused me to scratch my head bald, especially since I have trailer wiring plus camper wiring plus some sort of custom work the original owner did. 46 years of chaffing and it shorted out. I guess they don't make anything to last any more. I would check the entire system inch by inch. __________________ '69 GMC C2500 Custom Camper, 8 1/2' bed, New GM 350, NP 435 Close Ratio 4spd. Trans., 3.73 Dana-60 open.Camper and Trailer wiring, PS, PB, AC, tach , three gas tanks, stereo speakers, 2nd owner, Work-Truck supreme.

11-11-2015, 04:02 PM	#7
Andy4639 Old member Join Date: Jan 2002 Location: Liberty, & Garden City S.C. , U.S. Posts: 19,945	Re: 1970 pickup fuse blows when brakes and? Will it work fine up till you press the brake pedal is what I understand you are saying. So that tells me it's some place between the brake switch and the rear of the truck. As stated take one rear bulb out and see if it blows the fuse. If not put it back in and take the other side out and try it. If one are the other blows the fuse then look on that side of the wiring. __________________ 1971 LWB Custom, 6.0LS & 4L80E, Speedhut.com GPS speedometer & gauges with A/C. 20" Boss 338's Grey wheels 4 wheel disc brakes. My Driver Seeing the USA in a 71 Upstate SC GM Truck Club 2013,14 and 2016 Hot Rod Pour Tour http://upstategmtrucks.com/ Get out and drive the truck this summer and have some fun! It sucks not being able to hear! LWB trucks rule, if you don't think so measure your SWB! After talking to tech support at Air Lift I have found out that the kit I need is 60811. Per the measurements I gave them. Ride height of truck inside spring and inside diameter of springs.

11-13-2015, 01:23 AM	#8
Medhawk020 Registered User Join Date: Jul 2015 Location: YELM, Washington Posts: 8	Re: 1970 pickup fuse blows when brakes and? I had the problem on my 1970 C20. What I did was replace the wiring to the rear lights. There are two wires from the dash to the back.

11-13-2015, 04:54 AM	#9
camaney Registered User Join Date: Feb 2008 Location: sacramento california Posts: 204	Re: 1970 pickup fuse blows when brakes and? I replaced the headlight switch and that's it..it worked

11-13-2015, 09:59 AM	#11
Birza25 Registered User Join Date: Nov 2015 Location: Vancouver bc canada Posts: 4	Re: 1970 pickup fuse blows when brakes and? Thanks guys! Started going threw some wiring and found my hi/low switch on the floor was completely melted to the floor. Haven't had a chance to check the fuse yet. I checked the dome light wires they all look good. Po had changed the headlight switch. I still need to check the harness and so on. First c10 1969 shortbox 454/t400/12 bolt



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