gauge install problems

frcefedlx · Mar 21, 2009

I installed some Autometer gauges in a friends car and the water temp and the oil pressure gauge do not register anything at all. They are electrical and first the oil gauge, it came with a sender and according to the instructions requires one wire to send a signal and has a ground and 12volt hookup on back of gauge. everything was hooked up per directions and upon powering up, nothing. Same with the Water temp gauge, came with a sending unit and nothing from it as well. The instructions say the sender grounds itself with the threads. I do not understand why they do not work any input would be greatly appreciated. I have installed gauges in my previous and present car with no problems however I do not understand the one wire signal set up. Am I missing something?

toyman · Mar 21, 2009

frcefedlx said:
I installed some Autometer gauges in a friends car and the water temp and the oil pressure gauge do not register anything at all. They are electrical and first the oil gauge, it came with a sender and according to the instructions requires one wire to send a signal and has a ground and 12volt hookup on back of gauge. everything was hooked up per directions and upon powering up, nothing. Same with the Water temp gauge, came with a sending unit and nothing from it as well. The instructions say the sender grounds itself with the threads. I do not understand why they do not work any input would be greatly appreciated. I have installed gauges in my previous and present car with no problems however I do not understand the one wire signal set up. Am I missing something?

While I'm not familar with the Autometer gauge install, it occurs to me that if you used teflon tape on the threads you may have lost your ground connection.

Powering up (turning on the ignition) may be irrelevant to gauge operation. I would think that if there is only one signal wire the temp gauge relies on a bi metal strip that creates a voltage when heated by the coolant. Same principle would apply to the pressure gauge signal wire. The 12v on the gauge may just be for illumination. As I said, I'm not familar with the Autometer setup so this is just speculation on my part.

pirotec354 · Mar 22, 2009

toyman said:
The 12v on the gauge may just be for illumination. As I said, I'm not familar with the Autometer setup so this is just speculation on my part.

On the Autometer phantom style gauges they have two seperate power and ground connections for illumination but thats not to say that the style you used didnt. Like toyman said you may have lost your ground if you used the teflon tape. I used pipe dope on my tranny temp and oil temp senders and they worked just fine.

frcefedlx · Mar 22, 2009

no tape on either guage. Even tried to run a ground strap from threads to a chassis ground with no luck. I may try a different 12 volt source but I dont think that will change anything.

toyman · Mar 22, 2009

frcefedlx said:
no tape on either guage. Even tried to run a ground strap from threads to a chassis ground with no luck. I may try a different 12 volt source but I dont think that will change anything.

For clarification. You have the engine running and up to temp but the temp gauge still reads cold and the oil pressure reads zero. Any chance that you broke or chaffed a lead wire when pulling them through the firewall? I ask as the wires for my gauges are in the 24 gauge range and can be easily broken. Have you tested the power lead with a volt meter? And the reading is?

frcefedlx · Mar 22, 2009

Yes the car was driven to test the water temp gauge as well as seeing 12 volts at the back of the gauges. The oil pressure does absolutely nothing at startup and I would hope it would have pressure then and the water temp does not go anywhere after a good 20 minute drive. I would think that it could possibly be a bad gauge but it seems fishy to have two bad guages.

95Vert383AOD · Mar 22, 2009

Hmm i have a couple Autometer 1 wire sending unit gauges in my car. Did you use the Autometer sending units??? i don't believe these Gauges work with stock sending units.

HISSIN50 · Mar 22, 2009

Didnt read it real closely but the guys have steered you right. Dope on the threads should not greatly hinder how the gauge works. The nature of NPT threads mean they end up with metal to metal contact. You can ohm out your sender to chassis pathway. You should see about 1 Ohm. If not, you can grab a 18+ AWG wire, put an alligator clip on one end and ground the other. Connect the alligator clip to the metal sender to ground it (this is for diagnostics). The only time I've had to manually ground a sender was when it was suspended between two runs of rubber line.

As noted, be sure to use the proprietary sender for the gauge.

Check your power and ground with a DMM biased across each. You should obviously see 12 volts with the key on. Make sure you didnt confuse the gauge-power and lighting-power wiring, which would lead to the gauge only working with the lights on.

It'll be a simple solution since both gauges are acting up.
Good luck.

ProKiller · Mar 23, 2009

as Hissin said. make sure you have the power wires connected to the gauge properly. I had mine backwards on the one gauge and it didn't work. worth a shot to switch them around at the very least to rule that out.

frcefedlx · Mar 23, 2009

The coolant temp works now but because he is using it for the coolant in the vortech aftercooler it takes for ever to register. We will try a new twelve volt source for the Oil pressure but wont get to that for a few days. We are using the Autometer supplied sender for both guages and nothing is being used on the threads to prevent a bad ground . I think if a different 12 volt source does not fix it that would leave one of two things, bad sender or bad gauge. I still do not understand why there is voltage at the gauge but no activity.

ProKiller · Mar 24, 2009

just curious, why would you want to know the coolant temp of the aftercooler? wouldn't you rather want to know the air temp going into the engine. I just don't see what that data would provide you with.

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