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Old 02-03-2020, 11:18 PM
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67GP428 67GP428 is offline
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Default 1965 Gauges

I’m switching to a full gauge dash, from a warning light type. I bought the correct dash unit. Also bought a wiring harness new from America auto wire. Two pig tails go to the temp and oil behind the speedo pod. Does anyone here now where the leads go to? Any input will help.

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1965 Pontiac 2+2 421 HO auto
1967 Pontiac Grand Prix 428 4 speed- sold
1968 Firebird 400 auto - sold
1967 Bonneville Brougham 2 dr. hardtop. 1969 AMC Rebel SST wagon-sold
  #2  
Old 02-04-2020, 12:20 AM
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Bill Hanlon Bill Hanlon is offline
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You'll need to change the current oil pressure and coolant temp sensors from the "binary" type (either on or off) that run idiot lights to "analog" type that run gauges. The part number for the oil pressure sender for the '65 gauge is 1506191. The part number for the temperature sender is 1513321.

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Old 02-04-2020, 08:42 AM
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67GP428 67GP428 is offline
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Thanks Bill. My main question is where to tie in the wires from the guages? Need a wiring diagram if possible.

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1965 Pontiac 2+2 421 HO auto
1967 Pontiac Grand Prix 428 4 speed- sold
1968 Firebird 400 auto - sold
1967 Bonneville Brougham 2 dr. hardtop. 1969 AMC Rebel SST wagon-sold
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Old 02-04-2020, 01:22 PM
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Peter Serio Peter Serio is offline
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As far back as I can remember GM used a "color palette" for all their wiring harnesses. So once you know the circuit a specific color wire tells you something about that wire's purpose. If you have an original 1965 Big car speedometer cluster that has the optional oil pressure and coolant temperature gauges in it then each of those 2 gauges need 3 electrical connections to the car.

One connection is ground and that is not a wire at each gauge. The metal housing that the gauges attach to the back of the speedometer is the ground. On your car that may be a separate black wire; that or the housing may transmit ground via that huge chrome plated potmetal dash carrier to the steel dash or the cowl. The temperature gauge has a 2 wire plug-in on the back which should be a pink and a dark green wire. The pink wire is 12 volts battery + (key on) = zero volts (key off). The dark green wire is the seeker wire and it runs from the back of the gauge out thru the bulkhead plug-in at the firewall and into the engine compartment. It connects to the coolant temperature sender which is a thermistor. That sender is a sealed unit and it is therefor non-adjustable. The temperature sender is grounded to the engine block by it's threads (made from brass) into the coolant crossover.

Your oil pressure gauge; same deal: a 2 wire plug in on the back of the gauge: which has the pink (key on) 12 volt+ power wire and a dark blue wire in it. The dark blue wire runs out, thru the firewall same as the dark green wire under the hood and attaches to the oil pressure sender mounted just above the oil filter pad. Same deal as the coolant temperature sender. The threads of the oil pressure sender complete a pathway to engine block ground at the threads. GM car senders for red warning overheat & low oil pressure "lights" are NOT the same as for gauges. Just FYI: That coolant temperature sender has the be the original GM part # (as referenced in post #2 above) for that gauge to read correctly. (assuming the gauge works.) I have not seen any new aftermarket sender that is made properly that will read true with that year gauge.

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Last edited by Peter Serio; 02-04-2020 at 02:02 PM.
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Old 02-04-2020, 04:05 PM
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Stuart Stuart is offline
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There's a wiring diagram for 1965 big cars here: http://www.oldcarmanualproject.com/t...ing/index.html Unfortunately, it doesn't appear to show anything for gauges, just for idiot lights. I'd think there would be information in the factory shop manual if you have access to one.

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Old 02-04-2020, 10:51 PM
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Thank you guys for all of the information. I’m sure I can take it for here. Keep you posted.

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1965 Pontiac 2+2 421 HO auto
1967 Pontiac Grand Prix 428 4 speed- sold
1968 Firebird 400 auto - sold
1967 Bonneville Brougham 2 dr. hardtop. 1969 AMC Rebel SST wagon-sold
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