HELP Dash lights turning on with turn signals?

UC645

G-Body Guru
Apr 20, 2020
777
93
Kittanning, Pa
I’m currently fitting my dash permanently and while I was going over checks I bumped the turn signal on and had the dash lights come on.

The speedometer/tach cluster wasn’t pushed into place to lock into its stock connector and I don’t have the front light harness in place on the bulkhead connector. The only wires I cut on the speedo cluster harness were the gray for dash illumination and the pink with black tracer for power to the tach, everything else is stock.
This is on a GP dash harness
Any ideas?
 

UC645

G-Body Guru
Thread starter
Apr 20, 2020
777
93
Kittanning, Pa
Give it try with the front & rear light harnesses pluged in & grounded. By the way, was anyting added into the harness?
The lack of grounds turned out to be the issue. I don’t remember those lights coming on when I was bench testing this setup last year 🙃

Nothing has been added save for a couple of relays for the push button start I’ve wired in. I’ve only tapped into the ignition power and dash illumination on the speedo side and I’ve just added on to the wires for the warning light cluster fur gauges.

While I’m here, is there a wire for the oil pressure switch that I could tap into for an aftermarket sensor? I used the factory water temperature sensor wire and it works fine.
 

pagrunt

Geezer
Sep 14, 2014
7,863
113
Elderton, Pa
While I’m here, is there a wire for the oil pressure switch that I could tap into for an aftermarket sensor? I used the factory water temperature sensor wire and it works fine
If I'm remembering right, that's a gauge harness from thr GP so there should be a single tan wire with a rubber boot for the gauge sender. If not, that wire is tied into the three wire socket & if you're going to use the warning light as a back up a new lead will be needed. I'd run it to look factory & add it into the engine harness to run it through the bulk head conector.
 
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UC645

G-Body Guru
Thread starter
Apr 20, 2020
777
93
Kittanning, Pa
If I'm remembering right, that's a gauge harness from thr GP so there should be a single tan wire with a rubber boot for the gauge sender. If not, that wire is tied into the three wire socket & if you're going to use the warning light as a back up a new lead will be needed. I'd run it to look factory & add it into the engine harness to run it through the bulk head conector.
If the dash harness already has a tan wire, I should just need to add the tan wire to the engine harness, correct? I have a spare factory oil pressure sensor harness to use.
 

pagrunt

Geezer
Sep 14, 2014
7,863
113
Elderton, Pa
If the dash harness already has a tan wire, I should just need to add the tan wire to the engine harness, correct? I have a spare factory oil pressure sensor harness to use.
If I'm thinking right with the Pontiac harness, you should have the tan wire regardless being a gauge or warning light dash. Now if being gauge there will also be a dark green/white stripe wire for the choke light. Under the hood the warning light harness will have a plug for a two blade switch that has three wires, the tan, a brown & a light blue ones. The gauge one will replace the tan with the green/white one & the tan will be on its own. Keep in mind Chevy engines are like this with a electric choke which all carbed engines from '80 up (V6 since '78) are like this. If you engine set up don't need a power lead for the choke & have the gauge, you can use that green/white & de-pin it from the cluster plug to use it for your needs.
 
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UC645

G-Body Guru
Thread starter
Apr 20, 2020
777
93
Kittanning, Pa
If I'm thinking right with the Pontiac harness, you should have the tan wire regardless being a gauge or warning light dash. Now if being gauge there will also be a dark green/white stripe wire for the choke light. Under the hood the warning light harness will have a plug for a two blade switch that has three wires, the tan, a brown & a light blue ones. The gauge one will replace the tan with the green/white one & the tan will be on its own. Keep in mind Chevy engines are like this with a electric choke which all carbed engines from '80 up (V6 since '78) are like this. If you engine set up don't need a power lead for the choke & have the gauge, you can use that green/white & de-pin it from the cluster plug to use it for your needs.
Do you happen to have a pinout sheet for the engine harness? There’s no tan or green/white tracer wire in the harness I’m running up front, so I think this is the one i de-pinned for the factory sensor plug. Unless there’s a year spread that used something like a brown 16 gauge wire for the sensor.
 

pagrunt

Geezer
Sep 14, 2014
7,863
113
Elderton, Pa
Do you happen to have a pinout sheet for the engine harness? There’s no tan or green/white tracer wire in the harness I’m running up front, so I think this is the one i de-pinned for the factory sensor plug. Unless there’s a year spread that used something like a brown 16 gauge wire for the sensor.
That engine harness should be the same as your Monte's original but I'm not 100% as I only have Chevy diagrams. All the wires used for the oil warning/choke switch is listed as 18 gauge with the brown being the power wire for the choke. This & the alternator wire are the only brown wires in the engine harness. Now between the wire used & swelling from years of oil leeching into the wire jacket could make it look as if it 16 gauge. But you did de-pinned it so I'm not seeing anything else that brown 16 gauge could be. As for color usage, the only variant I've seen so far was '79 200 V6 cars with gauge/choke light used tan for both gauge sender & light switch. All other years was tan gauge & green/white choke light.
 
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