Instrument cluster voltage regulator - Upgrade?

[pippinmader]

I think my instrument cluster voltage regulator is not producing the correct voltage, everything reads low (oil reads 20psi , mechanical gauge reads 45 psi - temp reads 175F and I have a 195F thermostat). Replacement instrument voltage regulators cost a fortune ($30 for cheap Chinese one). I was considering making one using a solid state voltage regulator like a 7806

As you can see they are really cheap ($0.28) and are better than the stock ones because they actually produce a constant voltage no matter what the input is. My questions is has anyone done this? What voltage should I shoot for (5V, 6V, 8V?) Also does anyone know what the max current draw is on the gauges, most of these seem to only be good for 1.5A.

Of better yet, I looked on ebay for DC power supply and found lots of ones that can handle much higher currents like this one

[polecat]

Re: Instrument cluster voltage regulator - Upgrade?

Tried it on my '66 about 15 years ago. Couple problems, one I worked around, the other I didn't.

A 7806 is too high, and a 7805 too low. The gauges want about 5.5 volts *at around 70 degrees*. (more on that in a minute...). Stuck a 1N4001 diode in the ground leg (you can't ground the reg case doing that) and that got me pretty close.

The problem is that the Ford gauges are thermal, and apparently the stock (thermal/bimetal) reg is too. The gauges lose more heat in cold weather (read lower) so the stock regulator pulses longer to make up for that. My gauges read a good quarter scale low at "freezing" when calibrated at 70 degrees. I suppose you could work in a thermistor or something to compensate for that, but I never got that far. JL

[pippinmader]

Re: Instrument cluster voltage regulator - Upgrade?

Thanks polecat, that is exactly the kind of information I couldn't find anywhere else! I see that a couple places sell solid state instrument voltage regulators (wild horses for example) Do you know if they are temperature compensating?

I am a little surprised to hear that the voltage is so low, I though it was 6.6V or so. Maybe my best option is to go to the junk yard and grab a hand full of them and keep trying them out until I find one that makes my gauges read right.

[polecat]

Re: Instrument cluster voltage regulator - Upgrade?

Sorry, no idea on the aftermarket ones, I went back to a stock one. Lots of other Ford cars and trucks use the same one, and they rarely go bad. First one I grabbed at Pick Your Part did the trick on mine. Also make sure you have a good ground to the cluster - that can make the gauges read wrong, but usually too high.

The shop manual says the gauges need a constant 5 volts, but I tried that first, and it was too low. Half a volt changes the readings by maybe 1/4 scale if that helps. I don't know what they draw, but a voltmeter showed the 5 volts wasn't dropping with a 7805, so it must be less than 1.5 amps.

The other difference with a solid state reg was that the gauges were very slow to come up when I first turned on the key. I think the stock reg gives a full 12 volts for a short time before it starts pulsing, not a big deal, but thought I'd mention it. JL

[oleguy74]

Re: Instrument cluster voltage regulator - Upgrade?

disconnect sender wire from temp or oil sender.turn ign key to acc.connect voltmeter to sender wire.pulse should be 4-6 volts.if voltage is ok,with engine warmed up,disconnect wire on temp sender and read ohms of sender.57 ohms about=120* 25 ohms about is 190* 15 ohms is about 230*.oil pressure is 40 ohms 10 psi,30 ohms is 40 psi,13 ohms is 90 psi.fuel is 10 ohms full,21 ohms 3/4,25 ohms 1/2,33 ohms is 1/4,73 ohms empty.will try to post pic.