Instrument cluster lights 76 Cutlass

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Old September 9th, 2015, 12:35 AM
  #1  
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Instrument cluster lights 76 Cutlass

Hey guys, its been a minute. Decided to pull the cutlass out after sitting for a few years. The problem started before I parked it. Basically my instrument panel will not light up anymore. All of my dummy lights, gas guage and seatbelt lights work but not the actual light so that I can see what I'm doing in the dark. All of my exterior lights are working also. I checked the fuse and it looked fine, I replaced it anyways but no change. I read in some other threads to check the ground. From block to fire wall is fine but as far as under the dash I'm not even sure what I'm looking for. Any help would be appreciated.
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Old September 9th, 2015, 03:44 AM
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You do have the dash light dimmer on the headlight switch turned all the way up, right?
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Old September 9th, 2015, 07:37 AM
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Originally Posted by rocketraider
You do have the dash light dimmer on the headlight switch turned all the way up, right?
Yes sir, I forgot to put that in the OP.
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Old September 9th, 2015, 09:26 AM
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Had to ask. We've had a few cases on here that the car owner didn't know about the dash lights rheostat.


These clusters pull out from the front. Two, maybe three screws in each bezel and they'll pull out toward the steering wheel. You'll have to reach up behind the dash and loosen the speedo cable unless car has cruise, then you can disconnect it at regulator underhood and pull it out far enough to work.


There are pin connectors on each cluster. Before you pull the plugs, look at them closely to make sure nothing's broken and even then be really careful because these pins are known to break off the circuit boards. Then check ALL the cluster light bulbs. The gray wire in each pin connector is the lighting power feed.


If they're OK, next stop is the headlight switch. Again, the dash panel will pull out from the front; you might have to unhook the park brake cable to get it out far enough to work.


Look for a gray wire in the headlight switch connector. It's dash lights power feed. Do some continuity checks from red power feed to H/L switch and the gray wire (gray should be hot in park or head position) and notice whether the rheostat coil is clean and not burnt or broken.
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Old September 9th, 2015, 02:57 PM
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Originally Posted by rocketraider
Had to ask. We've had a few cases on here that the car owner didn't know about the dash lights rheostat.


These clusters pull out from the front. Two, maybe three screws in each bezel and they'll pull out toward the steering wheel. You'll have to reach up behind the dash and loosen the speedo cable unless car has cruise, then you can disconnect it at regulator underhood and pull it out far enough to work.


There are pin connectors on each cluster. Before you pull the plugs, look at them closely to make sure nothing's broken and even then be really careful because these pins are known to break off the circuit boards. Then check ALL the cluster light bulbs. The gray wire in each pin connector is the lighting power feed.


If they're OK, next stop is the headlight switch. Again, the dash panel will pull out from the front; you might have to unhook the park brake cable to get it out far enough to work.


Look for a gray wire in the headlight switch connector. It's dash lights power feed. Do some continuity checks from red power feed to H/L switch and the gray wire (gray should be hot in park or head position) and notice whether the rheostat coil is clean and not burnt or broken.
Thank you sir, I appreciate it. I'm going to buy a test light tonight and see what I can find out with the given info.

On another note, hoping you might know, I just found that the tong that connects to the bottom of the bulb in my reverse light is broken off. Can I repair it or would I have to find a whole new housing unit?
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Old September 13th, 2015, 12:59 AM
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Originally Posted by rocketraider
Had to ask. We've had a few cases on here that the car owner didn't know about the dash lights rheostat.


These clusters pull out from the front. Two, maybe three screws in each bezel and they'll pull out toward the steering wheel. You'll have to reach up behind the dash and loosen the speedo cable unless car has cruise, then you can disconnect it at regulator underhood and pull it out far enough to work.


There are pin connectors on each cluster. Before you pull the plugs, look at them closely to make sure nothing's broken and even then be really careful because these pins are known to break off the circuit boards. Then check ALL the cluster light bulbs. The gray wire in each pin connector is the lighting power feed.


If they're OK, next stop is the headlight switch. Again, the dash panel will pull out from the front; you might have to unhook the park brake cable to get it out far enough to work.


Look for a gray wire in the headlight switch connector. It's dash lights power feed. Do some continuity checks from red power feed to H/L switch and the gray wire (gray should be hot in park or head position) and notice whether the rheostat coil is clean and not burnt or broken.
OK so I finally got some time, bought a test light and re-checked all of my fuses - everythings good. Checked all of my dash light bulbs, working fine. I checked power to the grey wire on the first cluster and I'm getting no power. I looked around for any loose wires like a ground and I don't see any. I really don't know what to look for next? I got a wiring diagram from autozone but i don't really understand it 😀 Any help is appreciated.
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Old September 15th, 2015, 01:15 AM
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Originally Posted by rocketraider
Had to ask. We've had a few cases on here that the car owner didn't know about the dash lights rheostat.


These clusters pull out from the front. Two, maybe three screws in each bezel and they'll pull out toward the steering wheel. You'll have to reach up behind the dash and loosen the speedo cable unless car has cruise, then you can disconnect it at regulator underhood and pull it out far enough to work.


There are pin connectors on each cluster. Before you pull the plugs, look at them closely to make sure nothing's broken and even then be really careful because these pins are known to break off the circuit boards. Then check ALL the cluster light bulbs. The gray wire in each pin connector is the lighting power feed.


If they're OK, next stop is the headlight switch. Again, the dash panel will pull out from the front; you might have to unhook the park brake cable to get it out far enough to work.


Look for a gray wire in the headlight switch connector. It's dash lights power feed. Do some continuity checks from red power feed to H/L switch and the gray wire (gray should be hot in park or head position) and notice whether the rheostat coil is clean and not burnt or broken.
Hey boss sorry if I'm bugging you but no one else has commented. I went back in, couldn't get the cluster with the speedo off (not sure how to get speedo cable off). Opened up the headlight switch, red wire is constant hot. As for the grey wire, the only one I'm finding near the headlight switch is to the accessory light which isnt getting any power either. The rheostat looks clean no burns or breaks. I took pics if that helps any?
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Old September 15th, 2015, 01:17 AM
  #8  
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Originally Posted by rocketraider
Had to ask. We've had a few cases on here that the car owner didn't know about the dash lights rheostat.


These clusters pull out from the front. Two, maybe three screws in each bezel and they'll pull out toward the steering wheel. You'll have to reach up behind the dash and loosen the speedo cable unless car has cruise, then you can disconnect it at regulator underhood and pull it out far enough to work.


There are pin connectors on each cluster. Before you pull the plugs, look at them closely to make sure nothing's broken and even then be really careful because these pins are known to break off the circuit boards. Then check ALL the cluster light bulbs. The gray wire in each pin connector is the lighting power feed.


If they're OK, next stop is the headlight switch. Again, the dash panel will pull out from the front; you might have to unhook the park brake cable to get it out far enough to work.


Look for a gray wire in t inhe headlight switch connector. It's dash lights power feed. Do some continuity checks from red power feed to H/L switch and the gray wire (gray should be hot in park or head position) and notice whether the rheostat coil is clean and not burnt or broken.
Hey boss sorry if I'm bugging you but no one else has commented. I went back in, couldn't get the cluster with the speedo off (not sure how to get speedo cable off). Opened up the headlight switch, red wire is constant hot. As for the grey wire, the only one I'm finding near the headlight switch is to the accessory light which isnt getting any power either. The rheostat looks clean no burns or breaks. I took pics if that helps any? I did a direct power test to the dashboard lights and they worked fine so I'm thinking there not connected some where along the line? Am I missing something? IMG_20150915_003527_zpsmmxuxa2m.jpg

Last edited by 76_cutty; September 15th, 2015 at 01:31 AM.
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Old September 15th, 2015, 06:05 AM
  #9  
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76 Cutty, I feel your frustration and wish I could help. I haven't had any issues with the wiring on my 76 to be able to help you out. All I can say is try to test the wire as far back as possible, their may be a dead spot in the wire a some point. I will be following your thread as it will help me in the future.

Eric
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Old September 15th, 2015, 07:54 AM
  #10  
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Not ignoring you but I'll have to unpack my 1976 Chassis Manual to read the wiring diagrams.
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Old September 15th, 2015, 08:45 PM
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The green wire from the headlight switch feeds 12V to the 4 amp instrument panel lamp fuse. The wire is gray on the other side of the fuse. The gray wire feeds the instrument panel lamps as rocketraider said. The black wire on the headlamp switch and instrument panel plug is the ground. The ground is just as important as the 12V.

Check for power starting at the green wire through the fuse on the gray wire up to the instrument panel plug. If power is good then check the ground.

Don W
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Old September 15th, 2015, 09:09 PM
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So an easy step by step process would be to check for 12V at the following in the order listed.

Red wire at headlight switch
Green wire at headlight switch (with headlights on)
Check both sides of 4 amp instrument lamp fuse (with headlights on)
Check gray wire (with headlights on)

Don W
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