Packard Forum Index » V-8 (1955-56)

Now that the 55 is getting close to being on the road, it would be good to have the instruments working correctly.
Setting the stage: When starting the car, the in-dash oil pressure gauge showed O, but that’s ok since there is a mechanical gauge running off a T connection under the oil pressure sending switch. Cold idle shows about 30 psi. The gas gauge did not move off E, and the temperature gauge went to mid-range with a stone-cold engine Replace the temperature sending switch, but no change. Obviously look at instrument voltage limiter. Have a spare of unknown condition. Changed out limiter. Results were temperature gauge went to hot peg and fuel gauge went to half tank. Fuel tank has less than five gallons in it.
It seems that both limiters’ may be defective and a new one is needed?
Any and all comments as always are deeply appreciated.
Happy

The instrument voltage regulator is a mechanical device with a contact operated by a heater wrapped around a bimetal strip which opens and closes the contact with varying length cycles and pulses. The length of the pulses and the time between them results in 12v spurts for an average 5v to the gauges. In order for the regulator to work properly it must be grounded so that would be one question on the testing and substitution of another regulator. Here is what the voltage output looks like going to the instruments. Because of the short duration pulses an ordinary digital voltmeter sold for home use may be too slow to respond to the pulses and not be very accurate in trying to measure the output.

NOS regulators are available from our vendors and there have been some who have apparently used a small 5v solid state power supply from Amazon in its place. I have not tried that approach to know how successful the substitution has been but hopefully someone who has used one will see this post and chime in.

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Standard car USB chargers offer a 5V output. I wouldn't use one permanently, but for testing, you could presumably take a USB phone/tablet charger for a car (preferably one with a 2A output) and take a spare USB cable, cut it and strip the red and black wires (ignore the green and white) and attach to the power lugs of the gauge you are testing, with the instrument regulator and preferably other instruments disconnected. (Red +, Black −)

Howard is the instrument voltage regulator called out on the wiring diagrams for 55? I don't see it anywhere.

It is shown in the mounted location on the back of the cluster and like most things Packard replaced as a unit, diagrams just show wires going in and out of essentially a black box.

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I used a solid state regulator for a 55 clipper custom. It worked quite well. It involved using one made for reverse polarity and was mounted on a heat sink . For a senior you may need two due to 3 gauges, heat etc. it never failed when we owned it however it will be another thing to blow when an unaware reverses polarity on a jump start or charge. Look up # for 12- 5 v regulator and rev polarity one. Different part #.

BTW- we still have a 4gc, a roll of green embossed vinyl, stainless door edge guards, and some other trim and clips and the oil bath. If anyone needs will let go for reasonable offer or:as I have seen here- will ship all except carb and vinyl to anyone who pays shipping and makes a donation to the web page operator. I have considerable $ in the carb and vinyl so would not be giving these away.