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-   -   troubleshoot Instrument panel gauges (https://pontiacforum.com/pontiac/showthread.php?t=37113)

724mula September 11th, 2017 09:54 PM

troubleshoot Instrument panel gauges
 
Hoping someone here can help me troubleshoot my Rally gauges, oil,water and tach do not work, I don't know if the previous owner ever had them working. The IP does have lights blinkers high beam lights working but no gauges. It has a 12 pin plug to the IP is there a trouble shooting that harness and what readings I should get from the pins? The oil pressure gauge goes past 80 when ign. is turned on while the temp gauge does nothing. I have a diagram but it's got to be one of the worst I've ever worked with. Thanks

melsg5 September 12th, 2017 10:21 AM

you need a copy of the factory Pontiac shop manual which typically gives details on diagnosis and wiring diagrams. A guess on your problem would be the printed circuit board on the back of the gauge cluster.

724mula September 13th, 2017 06:54 AM

It's a newer printed circuit, I have the shop man, on cd, The gauges are newer also, does some one know what voltage I should be reading at the sender wires for the oil and water at the temp senders with key on not running?

melsg5 September 13th, 2017 10:01 AM

I've never come across a figure for the the voltage at the sender, I would assume 12 volts but the simple test is ground the wire and you should get a full scale reading on the gauge, disconnect the wire and you should get no reading on the gauge.

724mula September 14th, 2017 07:56 AM

do you know what sender part numbers should be in it? The previous owner say's he thinks he put the right ones in?? the harness to the water temp has a three pin plug which I found he had put a wire spade and wire to the Green terminal and taped off the plug, no power to the green or blue but power to the yellow in the plug, I don't see that harness in the wire schematics so I don;t know how it was wired originally.

724mula September 14th, 2017 07:58 AM

Quote:

Originally Posted by melsg5 (Post 106253)
I've never come across a figure for the the voltage at the sender, I would assume 12 volts but the simple test is ground the wire and you should get a full scale reading on the gauge, disconnect the wire and you should get no reading on the gauge.

looks like I only have 4.8 volts

melsg5 September 14th, 2017 09:38 AM

looking in the Firebird catalog from www.amesperf.com they show a single post water temp and oil sender for a 72 with gauges. See below what Ames says about the 3 terminal switch, it sounds like you are looking at the wrong one for water temp. Water temp is on the drivers side of the intake.
"For 1970-72, the three-terminal switch toward the passenger
side front is a transducer switch which is not available"

melsg5 September 14th, 2017 10:09 AM

The three wire switch on the passenger side is part of the TCS system explained in chapter 6D of the shop manual. TCS stands for temperature controlled spark. You only get full advance when the engine is up to operating temperature and the transmission is in high gear. The dark blue wire goes to TCS vacuum solenoid. The other two wires go to the firewall bulkhead connector and from there one, pink dbl blk, to the fuse box and the other, dk grn, to the temp light.

724mula September 14th, 2017 10:57 AM

Ah, Ok it's always fun trying to figure out what other guys have done to wiring, so I guess I'll look for a different dark green wire on the driver side, fun stuff :(. This car has gauges so your saying the green wire in the TCS would have went to a temp light and I suspect it would not get a signal unless hooked through the TCS? so I may have to try and figure out how to make this work. I'm not sure if the car had original lights or gauges. Thank You!

melsg5 September 14th, 2017 11:48 AM

you can get a copy of the original factory invoice from www.phs-online.com for a fee. That document would tell you if the optional gauge package was originally ordered. From the diagram I see in the 1970 hard copy manual, should be the same for 72, the dark green wire would only have power when hooked to the TCS temp sender. Do you see two senders one on each side of the intake?


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