Needles in gauges just peg out

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porksoda

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Well when I got my car it came with a extra gauge cluster because the one that was in was broken. The speedo was broken.
So yesterday me and a friend swapped out the gauge clusters and now the Temp gauge and Gasoline gauges just move across the whole gauge (pegging out).
My friend is telling me there is probably a electrical problem some where.
For now we unplugged the sending unit for the Temp gauge and Gasoline gauge so they actual gauge does not get messed up by pegging out every time the car turns one.
The needles move just fine across too if that makes a difference (very smoothly).

Any ideas why the needles keep pegging out?

Thanks alot!
 
There are two possible reasons I can think of:
- both sender leads are short circuited to ground (unlikely, but possible)
- the instrument voltage limiter has failed (more likely)

If the car does not have an oil pressure gauge, I'd consider replacing the limiter, which is a separate component plugged into the instrument cluster printed circuit board. You can test the limiter by connecting a voltmeter between the connector for the temperature sender and ground. The voltage should constantly fluctuate between 12 volts and 0.
 
This is the voltage limiter correct?

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If that part is what you are talking about we swapped them out between both clusters to see if we get another result.
They both did the same thing.
Either both of the limiters are bad or something else is wrong.

Do you think I should look into one of these new "Solid State Voltage Limiters"?

Here is a link:
http://cgi.ebay.com/ebaymotors/_W0QQcmdZViewItemQQ_trksidZp3984Q2em1423Q2el2649QQitemZ280572903071QQsspagenameZSTRKQ3aMEWAXQ3aIT

IMG_0169.jpg
 
Yes, replace the regulator with a solid state one from RTE. They work just fine. In the meantime don't run your car at all until it's fixed. You could blow out your gauges.
 
That's what the limiters look like on cars without the rallye dash (has no oil gauge). Anytime you replace the limiter, I'd recommend using one of the new solid state units as said above.

It sounds like the gauges themselves are OK. Seems like odds would be against having two bad limiters or both gauges being installed incorrectly, but it's possible. A test is in order before spending money on a new limiter.

Try this with the limiter that's not installed in the dash: attach the battery - terminal to the ground terminal, attach the +12 terminal to battery + and measure the voltage at the output terminal. I'm trying to find a diagram to confirm which terminal is which. If the limiter is bad, you'll see either zero or 12 volts at the output. If it's good, the voltage will oscillate between zero and 12 volts. If the limiter tests good, look for the problem elsewhere.

Another possibility is the ground connection for the dash is faulty, possibly the socket the limiter plugs into.

OK- based on what I see in this link:
http://www.allpar.com/history/mopar/electrical2.html

The terminal that connects to the metal shell of the limiter is ground, the middle terminal is +12 and the "angled" terminal is the output.
 
Another possibility is the ground connection for the dash is faulty, possibly the socket the limiter plugs into.

I would guess this IS the problem. My 67 has 3 brass springy fingers inserted into cutouts in the PC board which contact the limiter.

NONE of them were making reliable contact with the board. Solder the brass fingers to the board
 
when electricial systems do all kinds of goofy things.. Open ground, no doubt. Buy a power probe, get a schemetic and start checking
 
So yesterday me and a friend swapped out the gauge clusters and now the Temp gauge and Gasoline gauges just move across the whole gauge (pegging out).
My friend is telling me there is probably a electrical problem some where.
For now we unplugged the sending unit for the Temp gauge and Gasoline gauge so they actual gauge does not get messed up by pegging out every time the car turns one. !
You did the right thing disconnecting the gauges, because they will both be destroyed if they are left pegging out for a while.
What you are calling the sending unit for the Temp gauge and Gas gauges may be the voltage limiter. It's usually plugged into the instrument cluster.
The problem is apparently that your voltage limiter has died. That limiter has a bi-metallic strip that continuously makes and breaks contact with the 12v from the electrical system. Eventually, the limiter wears out and the output of the limiter becomes a continuous 12v instead of a stream of 12v pulses. The gauges can't handle the higher voltage and peg out. Pretty soon, the gauges themselves burn out and read nothing. At that point, all you can do is replace the regulator and the gauges (temp and fuel).
When this happened to me, I bought two instrument clusters (for the temp and gas of gauges) before I figured out what was happening.
If that part is what you are talking about we swapped them out between both clusters to see if we get another result.
They both did the same thing.
Either both of the limiters are bad or something else is wrong.
It makes sense that both limiters are bad. Because of the nature of the design, they won't last forever. They are so old now that they have all lived past their estimated lifetimes.

Thank your lucky stars that you disconnected the power to the gauges before they were destroyed. You did good! I didn't do that and it cost me a lot of money, time and frustration.

I'm an electronics tech and made the Radio Shack homemade substitute that I found on a Chrysler Imperial website. After experiencing the annoying inaccuracy of it, I finally sprung for the electronic version that RTE sells. It took me a year of frustration to convince me to spend the money for it, but I've never had to think about the gauges since then.
I've been able to move on to other problems the car has and continue with the learning and fun.

The NTE site has a chart that lists the problems with the Radio Shack version, and I can tell you they are accurate.

Sorry for the long post, but I dealt with the same problem for almost two years before finally solving it. I don't want others out there do go through what I did.
 
Ill do my best on this because its hard to explain.My gauges did exactly the same thing and what it was is there is a connection on the back with a black cap on it you have the wrong wire on it. I dont remember the color but check it out I think that might take care of the problem.Gook luck
 
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