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#1
08-14-2012, 04:54 PM
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72 Rally Gage Temp Pegged
I done a bunch of searching, and have read conflicting info. Sorry if it seems like I am repeating, but:
I have a 72 lemans that had idiot lights and the fasten seat belt warning. I got a set of rally gages that also have the fasten seat belt warning. I had the gages checked and a new circuit board installed. My temp gage remains pegged at 250. I have one temp sender using the green wire. I have tried an original sensor (850 ohms at room temp) and a Napa sensor (550 ohms at room temp). The gage remains pegged when the sensor wire is removed. I have read that the wire harness is a direct plug in for late 72's (including the PY tech that I got the circuit board from), yet other guys swap 2 wires, change 5 wires, and disconnect a check circuit. My oil pressure and fuel gages work, and the gages light properly. I havent tried blinkers, high beams, or other things yet. What am I missing? Thanks, Mike |
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#2
08-14-2012, 05:37 PM
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You would have to change 2 wires at the point the harness plugs into the guages. I'm sorry I don't remember which they are. Everything else would be OK. If you have a service manual you'll be able to see the wires that need to be swapped.
__________________
1964 GTO Auto 1970 GTO Ram Air III 4-speed 1972 Lemans Convert with endura option, 455, 4-speed |
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#3
08-14-2012, 06:01 PM
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__________________
Regards, "455HO" Lloyd 2008 GMC Sierra Denali 2WD Crew, L92 6L80E, Silver w/ Ebony guts, 14.26 @ 98 
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#4
08-14-2012, 08:44 PM
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I will have to look at it closer tomorrow, but the post says to switch 5 and 7 (tan and brown). My #5 is green, because the wire harness changed mid year in 72.
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#5
08-16-2012, 05:03 PM
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Problem Solved
I worked with Gentry at AutoInstruments to figure this out. The gage is supposed to be grounded at the silver post (the other 3 are copper). When I hooked up a dedicated ground wire, it started working fine. I assume that this means that the cluster was not assembled properly, or that something worked loose during shipping/install. I'm just glad it works. I don't like flying blind on temperature when I don't have a fan installed yet....
And I did not have to switch any wires in the harness. I found some schematics of the circuit board on this forum (copied here), and it shows that the wiring connector is identical. Mike |
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#6
08-16-2012, 05:06 PM
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Gage circuit boards for 72 Pontiac with Seat Belt Warning
Here are the circuit board diagrams for the gage clusters. The plug detail on the right shows that no wires need to be switched when you have a late 72 with the fasten seat belt warning. These were on a post from Half Inch Stud a while back.
Have Fun, Mike |
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#7
08-17-2012, 12:26 PM
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Sounds like the circuit to the sender is grounded out.
__________________
1971 Pontiac GT-37 Car is a junk yard dog and maybe one day will be restored. 
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