mystery short

classic Classic list List threaded Threaded
21 messages Options
12
Reply | Threaded
Open this post in threaded view
|

mystery short

baddog8it
A few weeks ago I replaced the turn signal assembly.  All appeared well, until over a week later when I went to get off a highway exit and after tapping the brakes I found that the cruise was not disengaging - I had to disengage via the steering wheel control.  Finally figured out that the number 1 fuse (brakes) was blown.  I'm guessing that it has been this way since replacing the turn signal assembly, but since I don't use the cruise very often, it's symptoms did not appear.

I have replaced the fuse multiple times trying to figure out under what combination of conditions it finally blows.  I'm about to get a re settable circuit breaker so that I stop burning thru fuses and stop crawling under the dash.

When it is blown, the turn signals still work normally (and when it's not blown).

It does not appear to be associated with the brake switch, turning of the steering wheel, engine running/not running, headlights.  With a new fuse, the hazard lights work.  There seems to be a time lag between the condition (whatever it may be) and the actual blowing of the fuse.  I did get it to act funny when simultaneously using the hazards and trying the turn signals.

I'm guessing that maybe I miswired the C305 connector, or if the rotating contacts inside the steering wheel are off.  I did use dielectric grease on the rotating contacts - is there maybe a low electrical leak?

I would think that if the C305 connector was miswired, I'd see some other function not working and the fuse blowing would be immediate.

I'm debating just disconnecting the C305.  If the problem is here or in the steering wheel, then at least I'll have brake lights (but not horn, turn signals or cruise) until the problem is fully identified.

Any ideas?

Now that I'm thinking about it, I'll try honking my horn - see if that has any relationship to the fuse blowing.
THE BEAST - '85 F350 2WD (non dually) Crew Cab, 460 carbureted, C6 tranny
Reply | Threaded
Open this post in threaded view
|

Re: mystery short

vjsimone
This post was updated on .
Horn - Fuse #16
Turn Signals - Fuse #5
Speed Control - Fuse #6
Check that your Stop Lamp Switch (Brake) is not shorting to ground.
Check that your Hazzard Switch is not shorting to ground.
Check your Trailer connections.
Have you replaced your Flasher Module?
Speed Control Amplifier could be drawing to much current.
You could put in a smaller fuse to see if you can get the Brake, Hazzard or Speed Control to trip alone.
Also check for a drain on that fuse with none of the above turned on.
Vinny... "Do All Scheduled Maintenance Prior To Troubleshooting" "Resolve All Known Issues Prior To Troubleshooting"
Reply | Threaded
Open this post in threaded view
|

Re: mystery short

baddog8it
This post was updated on .
Good food for thought.  I'll give some of that a try.  Thanks!

I don't think that it's the brake switch.  I've jiggled wires and pump the pedal and didn't get it to short.  When I did get the fuse to blow one time, there was no brake pedal involved.

I recognize that the horn and signals are on other fuses, but didn't know if maybe a miswiring or shorting within the steering contact rings could cause an overload across different circuits.

I was kind of going on the assumption that this problem is related to my most recent work that I'd done.
THE BEAST - '85 F350 2WD (non dually) Crew Cab, 460 carbureted, C6 tranny
Reply | Threaded
Open this post in threaded view
|

Re: mystery short

baddog8it
Another clue.  Never noticed before, but with a new fuse, the brake lights are on.  No matter what I do (press brake pedal, turn on/off headlights, turn signals, hazards), they stay on.

If I turn on the hazards, they work. But if I turn on the turn signals while the hazards are on, the hazards 'freeze' on and stay on.  From that point on, the hazards, when turned on, do not flash - you just see the dash indicators on solid.

It took some time, but after all of that testing, the fuse finally blew as I pulled out of the gas station.

Will check the brake switch itself later this morning, but I can't believe that this switch by itself will cause the fuse to blow.  
THE BEAST - '85 F350 2WD (non dually) Crew Cab, 460 carbureted, C6 tranny
Reply | Threaded
Open this post in threaded view
|

Re: mystery short

baddog8it
Pulled the connector off of the brake switch.  All appears right with the world now.  Will see if it continues to behave while I purchase a new brake switch.

Something in the back of my little brain is still bugging me though...
THE BEAST - '85 F350 2WD (non dually) Crew Cab, 460 carbureted, C6 tranny
Reply | Threaded
Open this post in threaded view
|

Re: mystery short

baddog8it
So, while parked, no lights on, nothing amiss.

Started my drive to the auto parts store, and I here the snap of the fuse after about 2 minutes of driving.

This tells me that there is a leak/short thru the hazard flasher or in the wiring between the fuse the brake switch.

I then pulled the hazard flasher and reconnected the brake switch.  With that combo, my brake lights are constantly on, but dim.

Next step - start pulling individual wires from the C305 connector.  If I don't have hazard lights, I won't miss them much.  In over 30 years of driving I've only used them a handful of times.
THE BEAST - '85 F350 2WD (non dually) Crew Cab, 460 carbureted, C6 tranny
Reply | Threaded
Open this post in threaded view
|

Re: mystery short

vjsimone
This post was updated on .
"I then pulled the hazard flasher and reconnected the brake switch.  With that combo, my brake lights are constantly on, but dim. "

So what happens when you disconnect the brake light switch?
Brake lights go out?
Vinny... "Do All Scheduled Maintenance Prior To Troubleshooting" "Resolve All Known Issues Prior To Troubleshooting"
Reply | Threaded
Open this post in threaded view
|

Re: mystery short

vjsimone
In reply to this post by baddog8it
"Started my drive to the auto parts store, and I here the snap of the fuse after about 2 minutes of driving. "

Did this happen after depressing the brake?
Vinny... "Do All Scheduled Maintenance Prior To Troubleshooting" "Resolve All Known Issues Prior To Troubleshooting"
Reply | Threaded
Open this post in threaded view
|

Re: mystery short

baddog8it
Nope, no brake used (shouldn't have mattered anyway - brake switch was disconnected).

Yes, when brake switch connected and hazard flasher removed - brake lights on (dim).
THE BEAST - '85 F350 2WD (non dually) Crew Cab, 460 carbureted, C6 tranny
Reply | Threaded
Open this post in threaded view
|

Re: mystery short

vjsimone
Disconnect your brake light switch to see if your brake lights are still on.
Vinny... "Do All Scheduled Maintenance Prior To Troubleshooting" "Resolve All Known Issues Prior To Troubleshooting"
Reply | Threaded
Open this post in threaded view
|

Re: mystery short

baddog8it
when brake switch disconnected, there are no brake lights (but running lights work normally)
THE BEAST - '85 F350 2WD (non dually) Crew Cab, 460 carbureted, C6 tranny
Reply | Threaded
Open this post in threaded view
|

Re: mystery short

vjsimone
This post was updated on .
I quess you are going to have to check the wiring you did.
Seems you are also not getting a good connection in there for the brake light pass thru,I suggest you clean off the grease you applied.
With the flasher removed & the brake switch disconnected you should not blow a fuse, unless there is a short in a wire somewhere in the path to the flasher of brake switch.
Vinny... "Do All Scheduled Maintenance Prior To Troubleshooting" "Resolve All Known Issues Prior To Troubleshooting"
Reply | Threaded
Open this post in threaded view
|

Re: mystery short

vjsimone
In reply to this post by baddog8it
FYI - dielectric grease is an insulator and inhibits current flow.
Vinny... "Do All Scheduled Maintenance Prior To Troubleshooting" "Resolve All Known Issues Prior To Troubleshooting"
Reply | Threaded
Open this post in threaded view
|

Re: mystery short

grumpin
Vinny mentioned to check the trailer wiring. I second that.

When I got my truck I needed to replace the turn signal switch, one of the tabs that hold the turn signal on was broke.

Afterwards, IIRC, I was also blowing the fuse for the brake lights and my tail lights were intermittent and the license plate lights were not working.

The trailer wiring had been spliced into and wired incorrectly. Ended up getting it all out where I could see it and got the EVTM out and straightened it up, been fine since.

Hope you get this soon, these kind of problems can drive you nuts.
Dane
1986 F250HD SC XLT Lariat 4x4 460 C6-Sold
1992 Bronco XLT 4x4 351W E4OD
1998 GMC Sierra SLE K1500 350 4L60E
Arizona
Reply | Threaded
Open this post in threaded view
|

Re: mystery short

baddog8it
So last night I dug back into it.  First I double checked my wiring at the C305 connector - all was fine.  Then pulled the steering wheel.  Low and behold, this is what I found...

I cleaned up everything, used some liquid tape to insulate the exposed copper, and tucked it away out of harms way.

I was confident that that a bare wire rubbing on the steering wheel had to be the problem and set about putting everything back in place - fully wrapping it up.  Reinstalled brake switch connector, hazard flasher and verified I had a good fuse in place.

UGH!!  Symptoms still exist (at least some of them).  I unplugged the brake switch connector so that I'm not running down the battery.  Everything still seems to act the same with the possible exception of the fuse shorting.

I think that either the flasher/turn signal assembly is wired wrong or has an internal short, or there is a problem in an aft wiring harness as others have alluded to.  I'll have to wait for the driveway to dry off enough so that I can go crawling around under the rear end of the beast!

thanks for the support and helpful info!  Hopefully I can get this resolved quickly.
THE BEAST - '85 F350 2WD (non dually) Crew Cab, 460 carbureted, C6 tranny
Reply | Threaded
Open this post in threaded view
|

Re: mystery short

baddog8it
This post was updated on .
Quick question - I don't have a build sheet available, so what's the simplest way to determine if my beast has the factory trailer wiring?

Edit - a bit of clarification.  Looking at the '85 EVTM on page 134, it appears that the 'TRAILER OPTION' includes a 'TRAILER ELECTRIC BRAKE CONTROL' which is attached to the brake pedal.  Compare that to the diagram on page 79 (showing turn/brake lights), there are greyed out areas labelled 'TRAILER ONLY'.  Are these areas and items labelled 'TRAILER ONLY' the same as the 'TRAILER OPTION'?

i.e.. If I don't have the trailer option, I can and should ignore anything labelled 'TRAILER ONLY'?
THE BEAST - '85 F350 2WD (non dually) Crew Cab, 460 carbureted, C6 tranny
Reply | Threaded
Open this post in threaded view
|

Re: mystery short

grumpin
Dang it! I don't remember well anymore. I had that same thing happen, it was blowing my fuse, then I found the trailer wiring all messed up because of my tail and license lights.

On the trailer option, I believe you will have a trailer lamp relay by the fuel pump relay on the left firewall to the left of the brake master cylinder. Also you will find wires that are white with a red dash for your year I believe, at the trailer plug. Also a bigger yellow wire for 12v trailer power.

HTH!
Dane
1986 F250HD SC XLT Lariat 4x4 460 C6-Sold
1992 Bronco XLT 4x4 351W E4OD
1998 GMC Sierra SLE K1500 350 4L60E
Arizona
Reply | Threaded
Open this post in threaded view
|

Re: mystery short

vjsimone
This post was updated on .
In reply to this post by baddog8it
Yeah, that White/Red wire with the bare spot is the 12v power to the switch from Fuse #1 via the Hazard Flasher, if that shorts, bam, fuse #1 gone, so you have found one problem.
Vinny... "Do All Scheduled Maintenance Prior To Troubleshooting" "Resolve All Known Issues Prior To Troubleshooting"
Reply | Threaded
Open this post in threaded view
|

Re: mystery short

vjsimone
This post was updated on .
In reply to this post by baddog8it
Also look on your brake pedal to see if you have a Brake Controler.
Vinny... "Do All Scheduled Maintenance Prior To Troubleshooting" "Resolve All Known Issues Prior To Troubleshooting"
Reply | Threaded
Open this post in threaded view
|

Re: mystery short

vjsimone
In reply to this post by baddog8it
So, you are replacing the Brake Light switch right?

In the mean time, jump the 2 wires for the Brake Light switch to see if the lights get brighter.

Also check connector 305 for bent pins/blades.
Vinny... "Do All Scheduled Maintenance Prior To Troubleshooting" "Resolve All Known Issues Prior To Troubleshooting"
12