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Ref: 1970 Cutlass. When installing the new Rally Pac Oil/ Temp/ Fuel module I rearranged the wiring to the module connector per the attached picture. Then cut the green wire in the steering column. Here is my issue - When I plug in the connector to the new module (screwed in for grounding), only the Temp gauge works (yes both Temp and Oil sensors were replaced), no fuel gauge no module lights or gen warning light.
When I removed the connector from the module and performed a circuit test on the wires (I removed them from the connector), I only get a signal from the pink 12v wire and the Green Temp wire. I should be getting signal from all the wires - correct?
Where did I go wrong, why aren't the rest of the wires producing signals?
The only purpose of the green wire at the ignition switch is to provide a ground to test the bulb. When you turn the ignition key past run (but before you get the the crank position) you get to bulb test. You won’t feel the detent in the key rotation, but it’s there. You technically don’t have to cut the wire, the only issue is the temp gauge will go full tilt hot when you crank the engine.
All the gauges are powered by the same ignition feed on the pink wire. The sending units provide the grounds. When you turn the info toon on, what do the gauges do? If the oil pressure reads zero, unhook the wire from the sending unit, the gauge should go full tilt high.
What does the fuel gauge read with the key on? If it’s reading past full, the sender wire is most likely open.
Since everything worked prior to swapping gauges, either you don’t have the gauge cluster well grounded (there is a small jumper wire from the gauge to the speedo if I remember correctly) or the gauge itself is defective.
Before going any further, run a jumper wire from the gauge housing to a good ground under the dash. If everything works, the you know your missing a ground wire under the dash
Update:
1. When I turn the key on, the Oil and Fuel are pegged past high, but they are that way with the key turned off. I unhooked the Oil Pressure gauge at the engine side and the dial is still above High.
2. There is no ground wire connection for the module, only at the mounting holes. I tried running a jumper from the mounting screw ground to a ground under the dash and nothing happened.
Ok, since both the oil and temp gauges are peg, that suggests and open circuit back to the sending units.
Plug the gauge back in, connect your ground wire to the gauge housing to a solid ground. With the key on, engine off, ground the wire to the oil pressure gauge. The gauge should read zero.
Next, find the tan wire in the trunk that goes to the fuel tank. There is a connector either in the trunk, or behind the license plate. Disconnect that plug. Turn the ignition on, ground that tan wire. The gauge should read empty.
Since everything worked before, I’m betting grounding wires doesn’t change anything. Double check to make sure you positioned the wires in the correct order, and in the correct spot in the connector. If so, I’m betting you either have a defective gauge cluster, or loose pins on the circuit board. You didn’t answer where you got the gauge, is it a OEM or reproduction?
Thank you for hanging in there with me, I will try your suggestions tonight and give you an update. Also I believe these are after Market, I bout them from The Parts Place:
If you have a meter, make sure you have continuity from the blue wire at the gauge connector, and the blue wire at the sending unit.
Make sure you have continuity between the tan wire at the gauge connector, and the tan wire at the fuel tank connector in the trunk.
With the key on, engine off, you should have power on the brown wire. That’s the alternator warning light power feed from the regulator. If that’s good, once again plug in the gauge harness. Unplug the 2 wire connector at the alternator. With the key on, engine off, ground the brown wire at the alternator plug. The alternator light should come on in the gauge cluster.
Once again, since everything worked before, there is no reason to suspect defective wiring now. Doing these tests ahead of time will give you some ammunition when you tell them the new gauge cluster is defective and you need a replacement.
Hi Matt, here's the update:
1. I checked the continuity from the Blue wire at the module connector and the connector of the Oil sending unit and received nothing with the key on or off.
2. Performed a continuity check on the tan wire on the connector in the trunk and the Fuel gauge pegged down with the key on or off.
3. I grounded the Brown wire on the Alternator connector and again nothing happened with the key on or off.
