Packard Forum Index » Post-War (1946-54)

Well Here I am again with the ongoing saga of my instrument cluster repair.... He he a LOT of fun :)

I have a question about the voltage regulator for the temp/gas gauges. I have grounded it with alligator clip lead and am taking a no-load reading between the regulator output and ground with my old trusty Simpson analog meter. The voltage is bouncing between 6v and 0v almost like a turn signal flasher would. I don't know how these old regulators operate. Do they need a load to operate properly or is this one toast? Also, how many amps are pulled through them? Can I pop in a modern 7905 voltage regulator in it's place? They are rated for 1A.

My Temp gauge always seemed to run high (Before and after a full service of the cooling system) And my gas gauge will only operate between 1/4 and 3/4 full. Previous owner just installed a new gas sending unit from Max Merritt before I purchased the car. Could these be symptoms indicative of a bad regulator AND a bad ground going to the cluster?

The regulator is most likely OK. It is a thermal affair which heats, breaks a contact, reheats, breaks etc at a speed depending on load to give an average sustained 5v out. The gauges are also thermal so are slow to respond and don't see the fluctuation.

The gas sender is probably at fault there. It sounds as if the phenolic support for the resistance element might be warped allowing poor contact with the wiper at certain spots. Specs on the senders are approx 10 ohms full or hot, 75 empty or cold. If you need a gas sender 57-9 Ford passenger uses an identical unit so is drop in. Here are a couple of placesclassiccarautoparts.com/gastank_sending_units_ford.html
secure435.hostgator.com/~dlvry40/ufolder/CgCat.php?onepart=B7A-9275-F

There was a running change on the temp gauge for complaints such as yours. Check out service counselor 27-4packardinfo.com/xoops/html/downloads/SC/SC-VOL27NO4.pdf and see if the symptoms match.

Thanks for the info.
I'm assuming the "regulator" in the service bulletin is just a dropping resistor. Do we know how many ohms?

I think it is a resistor too from the packaging, but don't recall ever seeing a value or any info for it. If it is, would guess 5 ohms or so. They would be increasing the total resistance to the gauge circuit so if cold is 75-78 and hot is 10 normally, then don't think it would be much more than that. If 51Packard or anyone else still has a dash apart and has that assumed resistor, maybe someone could measure it.

Also remember that those instrument voltage regulators put out a regulated 5v not 6v. They just do it mechanically via a "chopper" circuit.

If you looks at the part number, the same voltage regulator was used on the 12v 55/56 models as well. Also many Fords used 5v gauges well into the 1970s, and used basically the same type of regulator. So your local NAPA should still stock those regulators if needed.

Also clean grounds on the instrument cluster where it mounts to the dash, and also where the senders mount are essential.

My dash is still apart and I would love to help if I knew what you wanted me to measure LOL!

Appreciate it if you have it and could measure. There was a running change that came out in 53 and was applied to some 24, 25. 26th cars as needed-- so not all had it. It was probably a resistor added in the power feed to the temp gauge and is the black item labeled temperature gauge regulator. Suspect it was a resistor of fairly low ohms.

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I do not appear to have that on my cluster. I will recheck with my harness to see if I might have taken it off with it.

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Nope, yours still appears to be the original pigtailed feed.

My '54 did not have it on either. But my temp gauge is different so may not require it.