Factory Guage question

[will e]

Basic question: Do the temp/oil guages us constant voltage regulation or not?

Background: 30 years ago I converted my standard dash to a tach/guage cluster dash. I traced all of the wires, made as few splices as I could and moved the pins to the smaller connector used on the non-standard cluster.

Never had much of a problem. I haven't driven the car much. When I went to get it a while ago the gas gauge wasn't working. It was, but read just above empty no matter what. I drove it a little bit like this, maybe a couple of hundred miles.

I took the primary insterment cluster out. upgraded to LED lights. When I put it back in the gas gauge still reads just above E (it moves into that position with the ignition on) but the oil and temp gauges are not moving at all. I tried grounding one at the sender and no luck.

I am digging into it all and have wiring diagrams and notes. I always thought the guages were fed from the constant voltage regulator but now I am not so sure.

I am pretty good at reading electrical diagrams but, of course, I am handicapped by the fact I moved/spiced wires.

Thanks guys


I have dug into a little more and I believe they are voltage regulated.

 

[Don C]

You are correct, they run off the regulator. It sounds to me like the float arm rusted through or the float fell off or filled up with gas. Ground the wire that runs to the float, at the tank, if the gauge goes up, it's the float. If not it might be a loose or corroded connector between the tank and gauge.

 

[will e]

Thanks Don.

I got the gauge cluster out and tested the voltage going 'to' the temp/oil gauge. It jumps all over the place with the key turned on. So I 'bench' tested the regulator by applying 12v to the right side (looking from the back), ground to the ground and a meter on the other side and it jumped all over the place. I think the regularor might be bad. I will do some searching to see if my test was valid but, as near as I can tell, my constant voltage regulartor, well, isn't contstant.

What should be the voltage coming out of it?

 

[JimNiki]

Save yourself a lot of hassle and buy an electronic replacement..

 

[Don C]

Save yourself a lot of hassle and buy an electronic replacement..

+1

The original regulator works on a bi-metal contact, the bi-metal heats up and breaks the contact, cools down and makes contact. It uses a condenser to even out the voltage fluctuations. When the condenser goes bad the voltage bounces up and down.

 

[will e]

I thinks that's what I will do.


I figured out it attaches to the printed circuit board with fittings that remind me of a 9v battery (plus the screw that holds it in place). Got it off and bench tested it again and same thing, jumps all over the place.

The irony is I had taken the gauge set out to get my tach redone by rocketman. It was working but was inaccurate so I had him swap in his modern electronics and a new needle. So, for the first time since maybe before Clinton was president I have an accurate and working tach.

I did this because thad the car down for a few weeks while installing the GV overdrive. Years ago I swapped in 3.50 gears and never replaced the speedometer gear. With the new GV I had a new speedometer drive accurate to my axle/tires.

This was going to be the first time in a very long time my gauges all worked correctly (except the ALT, that's another story). And so the voltage regulator goes out on me. It was probably from all of the shuffling/moving around. The stock one is mechanical who knows what dirt and stuff got inside and then moved all around as I messed with the cluster.

 

[midlife]

You are correct, they run off the regulator. It sounds to me like the float arm rusted through or the float fell off or filled up with gas. Ground the wire that runs to the float, at the tank, if the gauge goes up, it's the float. If not it might be a loose or corroded connector between the tank and gauge.

What you are seeing is perfectly normal and expected when using almost every kind of volt-ohm meter (digital). The exception would be the old analog Simpson meters, which smooth out the fluctuations from 0 and 12V caused by the bimetallic strip. Average readings should be 5-6 VDC.

Probably your problem is poor contact between the CVR and the circuit card, particularly if both meters are going bad.

 

[Steve73QMach1]

The pulsating voltage regulator output is an indication that it is working OK. If you use a DC voltmeter, you will see the needle bounce back and forth. If you use an indicator light, it should flash on and off.