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Re-Wire Question - Gauge Cluster

jonesallu

Contributor
BigAl
Joined
Jan 2, 2022
Messages
45
Loc.
Brookings, SD
I acquired my fathers 1971 Bronco a few years ago - introduction posted in another thread. I've finally had some time to work on it. He installed a Centech wiring harness in the mid 90s. Then through the years, he had it at a garage occasionally for issues. I'm impressed with Centech's harness and appalled at the work the shop did. So, I removed everything that didn't belong and went back to a stock-ish setup using the Centech harness. I installed a stock ignition/start switch, installed a missing hazard switch, and installed a cigar lighter. All this was clearly marked on all the wires. Everything works flawlessly, including the turn signals now (ya!) and even the hazard switch works as it should (ya!, the wires were previously taped up in the dash), heater, windshield wipers, and whole nine yards. Everything. Important to note is that the turn signal indicators in the cluster work as they should. Given how nasty it is to get the headlight switch out, I installed a new Centech style headlight switch while I was there.

Until... I turn on the headlights. Everything exterior works as it should (all lights, running lights, headlights, low and high beams, turns signals and brakes - ya!). The left cluster illumination light works as it should (nice and bright). However, with the headlight switch in running lights only or with the head lights on low or high beam:
1) the top and right cluster illumination lights are 1/2 bright on the running setting and full brightness with the headlights on.
2) Both turn signal indicators lights are on and bright, and blink off when I use the turn signals.
3) The high beam indicator is always on, regardless of headlights off (running position), high or low beams.

IF, the one cluster illumination light didn't work correctly, I'd say it was a ground issue with the cluster case. However, the Centech harness runs separate ground wires to all the bulbs in the cluster and then ground at a common location on the body. However, it does seem like a ground issue to me. I do see that I ran the wire the wrong way through the amp gauge coil as it's reading backwards. That's an easy fix.

Any suggestions? Changing out the headlight switch is going to be the last thing I try. I'm 6'4" and 240 pounds. I barely fit in the seat - getting under that dash is pure hell. There is no wiring diagram that came with the Bronco and Centech did not use any common wire colors - however, again, the wires are all clearly marked with names. The Centech Installation Manual and Information Pamphlet that did come with the Bronco are not very helpful. I'm going to pop out the hazard switch and disconnect it as that is really the only new variable added to the harness. ???

Any suggestions?

Thanks,
Al Jones
1971 Bronco
Brookings, SD
 

JSBX

Contributor
Sr. Member
Joined
Mar 10, 2010
Messages
589
I can't help you with the wiring problem but when I am working under the dash I find it a little easier if I pull the drivers seat and put some cushions on the floor board. This way I can lay down with my feet toward the back and my back resting on the cushions. It is still a pain but at least I am a little more comfortable.
 

jamesroney

Contributor
Sr. Member
Joined
Sep 11, 2007
Messages
1,081
Loc.
Fremont, CA
I acquired my fathers 1

I acquired my fathers 1971 Bronco a few years ago - introduction posted in another thread. I've finally had some time to work on it. He installed a Centech wiring harness in the mid 90s. Then through the years, he had it at a garage occasionally for issues. I'm impressed with Centech's harness and appalled at the work the shop did. So, I removed everything that didn't belong and went back to a stock-ish setup using the Centech harness. I installed a stock ignition/start switch, installed a missing hazard switch, and installed a cigar lighter. All this was clearly marked on all the wires. Everything works flawlessly, including the turn signals now (ya!) and even the hazard switch works as it should (ya!, the wires were previously taped up in the dash), heater, windshield wipers, and whole nine yards. Everything. Important to note is that the turn signal indicators in the cluster work as they should. Given how nasty it is to get the headlight switch out, I installed a new Centech style headlight switch while I was there.

Until... I turn on the headlights. Everything exterior works as it should (all lights, running lights, headlights, low and high beams, turns signals and brakes - ya!). The left cluster illumination light works as it should (nice and bright). However, with the headlight switch in running lights only or with the head lights on low or high beam:
1) the top and right cluster illumination lights are 1/2 bright on the running setting and full brightness with the headlights on.
2) Both turn signal indicators lights are on and bright, and blink off when I use the turn signals.
3) The high beam indicator is always on, regardless of headlights off (running position), high or low beams.

IF, the one cluster illumination light didn't work correctly, I'd say it was a ground issue with the cluster case. However, the Centech harness runs separate ground wires to all the bulbs in the cluster and then ground at a common location on the body. However, it does seem like a ground issue to me. I do see that I ran the wire the wrong way through the amp gauge coil as it's reading backwards. That's an easy fix.

Any suggestions? Changing out the headlight switch is going to be the last thing I try. I'm 6'4" and 240 pounds. I barely fit in the seat - getting under that dash is pure hell. There is no wiring diagram that came with the Bronco and Centech did not use any common wire colors - however, again, the wires are all clearly marked with names. The Centech Installation Manual and Information Pamphlet that did come with the Bronco are not very helpful. I'm going to pop out the hazard switch and disconnect it as that is really the only new variable added to the harness. ???

Any suggestions?

Thanks,
Al Jones
1971 Bronco
Brookings, SD
Yeah it's the ground.

Centech has a little wire that pops out near the ignition switch that needs to be grounded in order to prevent the dash lights from back-feeding the other instrument lamps thru the ground. You can see that the bulbs have a separate ground wire, and that wire goes back into the harness. They do not ground thru the housing.

I just happen to have a Centech harness on the bench in the garage right now. Let me know if you need pics, and I can send them.

James.
 

Viperwolf1

Contributor
electron whisperer
Joined
Aug 23, 2007
Messages
24,152
If you pull the fresh air box out on the driver side you can get to most of the cluster from under the hood.

Check your grounds at the front turn signals.
 
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jonesallu

jonesallu

Contributor
BigAl
Joined
Jan 2, 2022
Messages
45
Loc.
Brookings, SD
Yeah it's the ground.

Centech has a little wire that pops out near the ignition switch that needs to be grounded in order to prevent the dash lights from back-feeding the other instrument lamps thru the ground. You can see that the bulbs have a separate ground wire, and that wire goes back into the harness. They do not ground thru the housing.

I just happen to have a Centech harness on the bench in the garage right now. Let me know if you need pics, and I can send them.

James.
I'll look for that little bugger. I thought I had it grounded but perhaps not. If that's the issue, I'll owe you big time. I would appreciate some pics of what you're talking about, especially if it's on the bench. Any and all help is appreciated. Thanks!
 

jamesroney

Contributor
Sr. Member
Joined
Sep 11, 2007
Messages
1,081
Loc.
Fremont, CA
Here’s a pic of the ground. It’s buried into the harness, and ends up with at least 5 different grounds coming out the other end.
 

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jonesallu

jonesallu

Contributor
BigAl
Joined
Jan 2, 2022
Messages
45
Loc.
Brookings, SD
Here’s a pic of the ground. It’s buried into the harness, and ends up with at least 5 different grounds coming out the other end.
Thanks @jamesroney . However, isn't that the ground coming out of the windshield wiper pigtail? That's what it looks like in your photo. I'm pretty sure I have that grounded but will look to make sure. Thanks again.
 
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jonesallu

jonesallu

Contributor
BigAl
Joined
Jan 2, 2022
Messages
45
Loc.
Brookings, SD
Interesting update: If I run the grounds directly to the battery, no difference. If I disconnect the dash grounds (3 of them), absolutely no change. Hmmmm.
 
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jonesallu

jonesallu

Contributor
BigAl
Joined
Jan 2, 2022
Messages
45
Loc.
Brookings, SD
Follow-up with fixes:
Symptoms 1 and 3: the top and right cluster illumination lights are 1/2 bright on the running setting and full brightness with the headlights on; and the high beam indicator is always on, regardless of headlights off (running position), high or low beams. Solution: switch the high beam pigtail into the correct hole. Five demerits and loss of a weekend pass.
Symptom 3: both turn signal indicators lights are on and bright, and blink off when I use the turn signals. Solution: fix short in front right turn signal housing. It was shorting to the running lights and back feeding. No bonus merit points for the doing what I should have in the first place prior to posting.

Everything, now everything works as it should in the Bronco. Whew.

That is all.
Al Jones
 
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jonesallu

jonesallu

Contributor
BigAl
Joined
Jan 2, 2022
Messages
45
Loc.
Brookings, SD
Here’s a pic of the ground. It’s buried into the harness, and ends up with at least 5 different grounds coming out the other end.
@jamesroney : I ended talking with Centech on the phone. He said (Jim) that allllllllll those grounds in the dash are also connected to the same ground at the wiper motor. Hence, if none of the dash grounds are connected (which they were not as I received the vehicle), everything will still work fine. That added a lot of clarity for me in terms of the grounds. He didn't say anything regarding loads or fuses if the dash grounds are not connected but I took them all and properly grounded them anyway. I also ended up ripping out the entire engine bay wiring and redoing that too. There was an unneeded coil resistor and more inadequate grounds. I thought a nonworking temp gauge was wiring but it turned out to be the sender. I feel a LOT better about wiring now.

Al Jones
71 Bronco
Brookings, SD
 

jamesroney

Contributor
Sr. Member
Joined
Sep 11, 2007
Messages
1,081
Loc.
Fremont, CA
@jamesroney : I ended talking with Centech on the phone. He said (Jim) that allllllllll those grounds in the dash are also connected to the same ground at the wiper motor. Hence, if none of the dash grounds are connected (which they were not as I received the vehicle), everything will still work fine. That added a lot of clarity for me in terms of the grounds. He didn't say anything regarding loads or fuses if the dash grounds are not connected but I took them all and properly grounded them anyway. I also ended up ripping out the entire engine bay wiring and redoing that too. There was an unneeded coil resistor and more inadequate grounds. I thought a nonworking temp gauge was wiring but it turned out to be the sender. I feel a LOT better about wiring now.

Al Jones
71 Bronco
Brookings, SD
Thanks. I thought that was the case, but I didn't want to cut open this Centech harness to find the splice connection, which no doubt exists somewhere. That tells me that somewhere in the harness, there is a junction where all of those grounds have to intersect. I hope I never have to find it.

I'm glad that you got yours fixed.
 
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