Packard Forum Index » V-8 (1955-56)

I'm have problems with the gas gauge, water temp gauge and the oil pressure gauge working intermitten when I start the car. When they do work they fluctuate! I have replaced the dash voltage regulator twice and the same thing happens. It has been suggested that I put a ground wire from the gauge cluster to a good ground to be sure there is a good ground. Does anyone else have any suggestions?

What car do you have? If several gauges are intermittent, it suggests a poor ground at the gauge cluster. If the gauges have a dedicated contact in the ignition switch, it could be faulty. It might also be worthwhile to be sure that all fuses are good and making good contact.

I believe the only years that used an instrument voltage regulator were the 51-56 models having King-Seeley thermal type gauges. 55-6 models are supplied from the ign sw ACC terminal, thru a fuse on the under dash block, then to the regulator input on the back of the cluster. 51-3 regulators are powered from the GA terminal on the ign sw and thru the switched 10 amp AUX circuit breaker also bolted to the rear of the cluster, to the regulator input. 54 has an ign switch ACC terminal like the 55--6 switches but has the 10 amp AUX circuit breaker instead of fuses..

The gauges run on a stated nominal voltage of 5v which is provided by 6 or 12v on/off pulses out of the regulator. The regulator is also thermally operated and functions by opening and closing a contact to ground. Load determines the frequency and pulse duration of the 6 or 12v pulses and when the actual voltage on time is averaged, the result provides the nominal 5v value. Because of the short pulses an ordinary VOM may not be fast enough to convert and average the pulses to be able to accurately measure or display the output. Here is what the instrument regulator output looks like when running on 12v.




Unlike the earlier magnetic gauges used in some models, the thermal type gauges themselves do not need a ground but the regulator and senders do. Take extra care to ensure those all have solid grounds.. Make sure the regulator is tightly fastened to the cluster when adding your extra ground wire between the cluster and a cleaned and shiny area on the body sheetmetal. After removing and replacing a fuel tank many report issues with the fuel sender ground and teflon tape or sealant at the temp or oil sender also has caused issues.

Ford used the same 5v gauge regulator well into the early 70s.

Not knowing what year you have it hard to say exactly what the problem is, but if it's 51-56, then either the feed to voltage regulator is loose, or the regulator itself is loose and with an intermittent ground.

It could also been a weak circuit breaker or something downstream that has a short and is causing it to trip and reset quickly.

I have a similar problem to Ernie on my 55 400, the gas oil press and temp gauges seem to work at first then as things warm up all either drop to zero or sometimes work intermittently. I'll check earth connections.

Would substitution with a modern 12v/5v DC regulator work or would these gauges not work on stable 5vDC or worse could it fry the gauges..?

I tried using a modern "drok" voltage reducer. It sort of worked, but not very well. The gauges were a little funny. I went back to the original kind of reducer. It didn't fry anything, but was not very steady. Maybe if you had one reducer for each of the gauges, but that is getting kind of silly for accurate gauges.
Here is a link to my blog where I said I didn't like the modern voltage reducer after trying it out for a while.
Drok_in_Clipper_Blog

If you search for drok on this site, you can see my expereinces.

Well here is my latest installment of trying to get these gauges to work! After a day of testing(I had a friend work with me who knows about a lot of electrical issues, (he restores vintage radios) we decided to purchase a original dash voltage regulator,(I discarded the old one because I thought it didn't work, I could of been wrong) with the hope that would solve the problem. But No! I was able to see where the original voltage regulator was mounted, but there is no way I can reach in under the dash to put it in its original position. I don't even remember how I took the old one out, So I mounted it to the bottom of the dash where I can get to it easier. I also made a ground wire to attach to the back of the gauge cluster, which I attached to the mounting bolt of the dash voltage regulator. And it still does not make the gauges read!
I have tested the gauges (Again) individually to verify that they work! And they do! We are back to the thought that the gauge sending units are Bad! I have already replaced the water temp & oil Pressure sending units a couple of times with no luck!
I know we are going to sell the car, but I would like to say that everything works on the car to the next owner!
What am I missing? Any Advise!

First of all, you need to make sure all your connections are good. The water temperature and oil pressure senders screw in with a pipe thread so they almost always have a good connection to the block, but you need to make sure both the terminal, the face of the nut, and the threads on the rod are polished up with some steel wool. That being said, the stuff usually has to be pretty severely corroded in an obvious way to not work and require this sort of treatment.

When I have my gauges out of the car, I will check the proper operation using a continuous 5 volt supply from a power supply. You can use something like a 22 ohm resistor of a reasonable wattage inline between the 5 volts and the gauge which should make the gauge read at a moderate position. You can then power the voltage regulator with 13 volts and connect the output to the gauge and verify that the gauge reads in the exact same position. If not, you can recalibrate the voltage regulator by adjusting the spring tension slightly.

The senders can be checked using an ohmmeter. The fuel sender should be approximately between 70 ohms empty and 10 ohms full. The others have the same range but they are impractical to test the full value.

Assuming you have checked through these things, the only reasonable option left is something the wiring harness, but that would be very obscure. Are you using the original harness for the regulator to the gauges?

More info

packardinfo.com/xoops/html/modules/newbb ... ic.php?post_id=281093&keywords=ohms

Have you also verified you have a solid and constant 12v feeding the instrument regulator?

55-6 models have a fuse for the instrument feed located in the block under the dash. Under some conditions the fuse holding clips have been known to oxidize or corrode resulting in intermittent contact. The fuse itself can also have issues internally that are not easily seen and with a quick inspection, would look like a perfectly good fuse.

Another issue is the under dash fuse block -- in fact, almost all fuse holders of any type that Packard used over the years -- are sized specifically for SFE or AGW type fuses. Those particular type fuses vary in diameter and/or length that are amp rating specific. If someone has tried to cram or jerry rig a wrong size or type fuse with a different length or diameter in the block, the clips or their connections inside the block could have been damaged resulting in an intermittent connection. The specified fuse for the instrument slot is an AGW 7 1/2 amp fuse which has a size of 1/4" in diameter by 7/8" long.

For reference, here is a chart showing many of the fuse sizes Packard used. Most of them can be found at Napa and if a particular size fuse is completely obsolete and cannot be found, typically the holder will need to be changed to accommodate a more common 1 1/4" long AGC type or the more modern blade type fuse of the proper capacity.