'B' Body Rally Gauge Problem

Jacko G

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Hello fellow Pontiac enthusiasts!

I am posting on this forum hoping somebody has completed a conversion from idiot lights to Rally gauges for a 1973-1976 ‘B' body. Mine is a 73’ Grandville vert with the 455 motor. I have installed the rally gauges (all nos) a new rally gauge printed circuit (from Ames), and all new AC Delco sending units. My problem is that the only gauge I can get to read correctly is the temp gauge (only after running a jumper wire from the right side of the temp resistor to ground). With the car running, the fuel gauge needle indicator doesn't move at all, the voltmeter stays pegged, and the oil pressure gauge appears to read about 40 at idle. The oil pressure reading of 40 is reduced by 5-10 whenever the rpm’s are increased. I have spent many hours trying to correct these problems, but have not had any success. Does anybody have any thoughts or experience with these conversions? I would hate to reinstall the idiot lights, but have run out of options at this point. Thanks in advance for any help you can offer…
 

melsg5

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Have you used a multimeter to see what your alternator is generating?
Have you used a temporary mechanical oil pressure gauge?
What does the fuel gauge read, full or empty?
Do you have the 73 factory Service Manual?
 

Jacko G

New member
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Have you used a multimeter to see what your alternator is generating?
Have you used a temporary mechanical oil pressure gauge?
What does the fuel gauge read, full or empty?
Do you have the 73 factory Service Manual?
Alternator is putting out 14.0 v, fuel gauge stays on empty, I do have a 73 service manual, haven't used a temporary oil pressure gauge...
Thank you, melsg5
 

melsg5

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The fuel gauge reading empty tells me the signal from the gauge is grounded instead of going to the tank sender.
I would look at that printed circuit to see if something on it is grounding out such as you were supposed to use an insulating washer under a nut, etc. See if the manual shows anything.
If that is the case it may effect the other functions also.
Are there resistors on the back of the gauges and can you check them with an ohmmeter?
______________________________
 

Jacko G

New member
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The fuel gauge reading empty tells me the signal from the gauge is grounded instead of going to the tank sender.

I would look at that printed circuit to see if something on it is grounding out such as you were supposed to use an insulating washer under a nut, etc. See if the manual shows anything.

If that is the case it may effect the other functions also.

Are there resistors on the back of the gauges and can you check them with an
 

Jacko G

New member
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melsg5
I tested the oil pressure with a mechanical gauge and I have good pressure. I examined the printed circuit and can't find any obvious ground problems. I tested all gauge resistors and they all appear to be working properly. I did find a horseshoe shaped insulated washer mounted under the temp gauge resistor. There are 4 mounting studs on the back of the temp gauge. The insulated washer was connected at the 12. 9, and 6 o'clock positions (looking at the gauge from the front). I have pictures but for some reason am unable to attach any files to this reply. What do you suggest?
Thanks
 
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