| Stop lights blowing fuse [message #328222] |
Sun, 14 January 2018 18:41  |
xplorid
Messages: 213
Registered: February 2012
Location: Boise
Karma: 0
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Using the brakes is blowing the stop/dir/hazard 20 amp fuse. Trying to narrow the problem area (and using lots of fuses) the directionals and hazards work fine and activate the lights as they are supposed to. Guessing that the wiring to the rear lights is common to the dir/haz/brakes, does that eliminate the wiring going to the rear as the problem?
I just swapped the stop light switch and it made no difference. Push the brake pedal and the fuse will blow after a few seconds - I do not know if the brake lights are activated when this happens. The problem appeared suddenly, worked fine prior.
I am a fairly lame mechanic but especially crippled with electrical stuff. I have a multimeter and almost know how to use it.
Jeff
1974/94 GMCII by Explorer
Manny 6.5 TD Al radiator
1 ton front 4 bags back
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| Re: [GMCnet] Stop lights blowing fuse [message #328230 is a reply to message #328229] |
Sun, 14 January 2018 20:36  |
xplorid
Messages: 213
Registered: February 2012
Location: Boise
Karma: 0
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Thanks Tom that sounds like a plan. I have looked for a trailer harness in the past and never found one. This is a GMCII by Explorer, body off in 1994, and about every original circuit has been invaded or hacked, so I can never tell.
I'll let you know what I find, thanks for the guidance.
Sunny and in the 50s in Boise today, another day or two of that and I might get this fixed.
1974/94 GMCII by Explorer
Manny 6.5 TD Al radiator
1 ton front 4 bags back
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| Re: Stop lights blowing fuse [message #328233 is a reply to message #328222] |
Sun, 14 January 2018 23:17 |
Ken Burton
Messages: 10030
Registered: January 2004
Location: Hebron, Indiana
Karma: 10
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I assume that you have removed BOTH bulbs from the rear lights and tried to see if it blows fuses that way.
Ken Burton - N9KB
76 Palm Beach
Hebron, Indiana
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| Re: Stop lights blowing fuse [message #328235 is a reply to message #328233] |
Mon, 15 January 2018 08:42 |
xplorid
Messages: 213
Registered: February 2012
Location: Boise
Karma: 0
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Hi Ken - that was kind of my original question - if the flashers and directionals work as they should and do not blow the fuse, does that mean the problem is forward and not aft. All 3 functions use the same wiring and bulbs to the rear of the coach, right?
1974/94 GMCII by Explorer
Manny 6.5 TD Al radiator
1 ton front 4 bags back
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| Re: Stop lights blowing fuse [message #328239 is a reply to message #328222] |
Mon, 15 January 2018 09:18 |
JohnL455
Messages: 4447
Registered: October 2006
Location: Woodstock, IL
Karma: 12
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You could have a bulb with a compromised filament. This can draw more current. Try easy stuff first and you can inspect sockets while changing lamps.
John Lebetski
Woodstock, IL
77 Eleganza II
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| Re: Stop lights blowing fuse [message #328241 is a reply to message #328235] |
Mon, 15 January 2018 09:51 |
Ken Burton
Messages: 10030
Registered: January 2004
Location: Hebron, Indiana
Karma: 10
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xplorid wrote on Mon, 15 January 2018 08:42Hi Ken - that was kind of my original question - if the flashers and directionals work as they should and do not blow the fuse, does that mean the problem is forward and not aft. All 3 functions use the same wiring and bulbs to the rear of the coach, right?
You are correct. I need to go look at the wiring diagram to refresh my memory. I believe that the brake switch feeds the turn signal and 4 way flasher assembly on the steering column and then the wiring goes to the rear lights of the coach. So you are probably correct that the rear bulbs are not shorted. But... shorted bulbs and sockets are very common, so I might take them apart anyway just to make sure. I am wondering if there is something else besides the brake lights drawing power off of the brake switch.
There is a kill circuit for the cruise control also on that switch and it is wired to the brake lights. You might want to find that cruise control circuit and disconnect it. This might just be a bad / shorted brake light switch. I need to go look at the wiring diagram before I say too much more from memory and find out later that I am wrong.
Ken Burton - N9KB
76 Palm Beach
Hebron, Indiana
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| Re: Stop lights blowing fuse [message #328247 is a reply to message #328222] |
Mon, 15 January 2018 15:50 |
jhbridges
Messages: 8412
Registered: May 2011
Location: Braselton ga
Karma: -74
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I don't think you have eliminated the wiring to the read necessarily. I suspect since you say it takes a bit before the fuse blows you haven't a complete short. I'd look for a damaged wire, corroded switch or socket. One wire at a time...
--johnny
Foolish Carriage, 76 26' Eleganza(?) with beaucoup mods and add - ons.
Braselton, Ga.
I forgive them all, save those who hurt the dogs. They must answer to me in hell
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| Re: Stop lights blowing fuse [message #328249 is a reply to message #328247] |
Mon, 15 January 2018 16:12 |
xplorid
Messages: 213
Registered: February 2012
Location: Boise
Karma: 0
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The culprit appears to be the rear passenger side socket, right on johnny.
The hazard/directionals were not working properly as thought, just taking longer to blow because the power to stop light is not constant I guess. Following the circuit dark green (RH rear) wire found resistance in the contact at the socket. Cleaning did not help, needs to be replaced I guess.
Thanks for all the help and guidance, now to find a replacement socket. These are the somewhat modernized tail lamp lenses from the early 90s, not sure of the sockets are the same.
Jeff
1974/94 GMCII by Explorer
Manny 6.5 TD Al radiator
1 ton front 4 bags back
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| Re: Stop lights blowing fuse [message #328250 is a reply to message #328249] |
Mon, 15 January 2018 17:18 |
cadelec
Messages: 303
Registered: September 2011
Location: Brisbane Australia
Karma: 1
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high resistance will not cause the fuse to blow low resistance to frame will.
remove all the lamps to the brake lights and disconnect the switch at the brake pedal
then using your multimeter you should have a high resistance between the white wire at the brake switch and the frame of the coach
if not then you need to try and find where the short is .
as they say divide and conquer
Trevor
Brisbane Australia
Siesta Koala 76 Edgemont (old Bobby Moores)
71 Cadillac Eldo Convert
58 Cadillac Eldorado Brougham Project
[Updated on: Mon, 15 January 2018 17:19] Report message to a moderator |
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| Re: Stop lights blowing fuse [message #328251 is a reply to message #328250] |
Mon, 15 January 2018 17:59 |
xplorid
Messages: 213
Registered: February 2012
Location: Boise
Karma: 0
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Thanks mate, and sorry, should not have used the word "resistance", I do not know what I am talking about technically.
I pulled the dark green directional wire (RH rear) from the turn signal switch plug at the bottom of the column
Ran a long "jumper" wire from that pulled (turn signal switch) wire to the RH rear socket contact and got a very weak turn signal light, trying several spots on the contact.
Pulled that side of the contact out of the RH rear socket and the jumper wire operated the turn signal light correctly when connected directly to the bulb.
Cleaned the socket as best I could, put it back in the socket and tested again with the same results. Did that 3 times, thinking I had found the bad spot in the circuit.
Hope that makes sense, no knowledge but a little logic.
To be safe, I left the dark green directional wire disconnected at the plug at the column, now everything works except the RH rear stop light/directional light, and the fuse does not blow.
At least for the moment I can move the coach with a single (LH side) brake light functioning and 3 out of 4 directionals.
That's as close as I am going to get today, not sure what I am missing yet.
Jeff
1974/94 GMCII by Explorer
Manny 6.5 TD Al radiator
1 ton front 4 bags back
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| Re: Stop lights blowing fuse [message #328253 is a reply to message #328251] |
Mon, 15 January 2018 18:23 |
cadelec
Messages: 303
Registered: September 2011
Location: Brisbane Australia
Karma: 1
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if it is not blowing fuses now it sounds like you may have a short in the dark green wire to the RH stop. as for the dim lamp when in the socket make sure you have a good ground on theblack wire this should be close to zero ohms to the frame
Trevor
Brisbane Australia
Siesta Koala 76 Edgemont (old Bobby Moores)
71 Cadillac Eldo Convert
58 Cadillac Eldorado Brougham Project
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| Re: Stop lights blowing fuse [message #328254 is a reply to message #328251] |
Mon, 15 January 2018 18:28 |
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Matt Colie
Messages: 8547
Registered: March 2007
Location: S.E. Michigan
Karma: 7
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xplorid wrote on Mon, 15 January 2018 18:59Thanks mate, and sorry, should not have used the word "resistance", I do not know what I am talking about technically.
I pulled the dark green directional wire (RH rear) from the turn signal switch plug at the bottom of the column
Ran a long "jumper" wire from that pulled (turn signal switch) wire to the RH rear socket contact and got a very weak turn signal light, trying several spots on the contact.
Pulled that side of the contact out of the RH rear socket and the jumper wire operated the turn signal light correctly when connected directly to the bulb.
Cleaned the socket as best I could, put it back in the socket and tested again with the same results. Did that 3 times, thinking I had found the bad spot in the circuit.
Hope that makes sense, no knowledge but a little logic.
To be safe, I left the dark green directional wire disconnected at the plug at the column, now everything works except the RH rear stop light/directional light, and the fuse does not blow.
At least for the moment I can move the coach with a single (LH side) brake light functioning and 3 out of 4 directionals.
That's as close as I am going to get today, not sure what I am missing yet.
Jeff
Jeff,
I am straining at some very old neurons here, but GM went though several versions of sockets for brake/tail light assemblies. I had some trouble with most. The two I remember best are:
One that had the two contacts though a piece of phenolic. That contact was crimped onto the wire and the contacts and all were loaded into the socket with a spring. With time and age, the phenolic would let the back side of the contact down so it could short to the spring. The spring was not a real hard short, but the current would soften it. And a guy without a lot of patience would end up throwing things because you could pull the bulb out and clean thing and it would work until it didn't again.
The other was a trip too. They had a rubber plug with the contacts in it. This is no better. The rubber goes bad with age and will create a very reliable intermittent short in the light circuit. You will never find it unless you pull the whole assembly apart.
Now, What to do if this sounds like your case.
Go to a local store front autoparts store and look for the wall of electrical stuff. Someplace will be a double contact socket with two wires. These come in both the king that fit in a big hole and the kind that are just a socket. Buy all you find that you think have a chance and save the receipt so you can take the others back. It may take some ingenuity to make this repair, but I have done it.
Matt
Matt & Mary Colie - Chaumière -'73 Glacier 23 - Members GMCMI, GMCGL, GMCES
Electronically Controlled Quiet Engine Cooling Fan with OE Rear Drum Brakes with Applied Control Arms
SE Michigan - Near DTW - Twixt A2 and Detroit
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| Re: Stop lights blowing fuse [message #328257 is a reply to message #328254] |
Mon, 15 January 2018 18:49 |
xplorid
Messages: 213
Registered: February 2012
Location: Boise
Karma: 0
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Senior Member |
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Thanks Matt - the rear lights and sockets appear to be listed as 1985 Chevy G20 Van at Auto zone as Part Number: 85832 (Dorman) $6.49 - it's a 3 wire socket
Trevor - the "short" is somewhere from the connector going to the rear (under dash on left drivers side) and the bulb, I thought my jumper antics identified the socket itself, maybe not.
For $6.49 I am going to find out tomorrow.
1974/94 GMCII by Explorer
Manny 6.5 TD Al radiator
1 ton front 4 bags back
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