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I read in another post that if your gauges are reading low that it could be the headlight switch ar dimmer switch.

my oil pressure, temp and fuel gauges all seem to read very low. how do I tell if its in the headlight , or dimmer switch?

any ideas ?? 77 w-100

thanks
 

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they say there is a relay ,on the back of the inst cluster..it is about 1 1/2 '' long 3/4 wide ...replace it it is the subject of an article in mopar mus... quinn
 

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i didnt notice until after the ans. ... but have you looked at the ok chapter bd if not, please do we need all we can get as members.... if you still have problems e me [email protected] any tyme qp
 

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It's called a voltage limiter, part number 3592899. That might be your problem. In my experience if it was your dimmer or your headlight switch your gauges would be reading high not low, but it could work the other way I guess.

Mac
 

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You may have a grounding problem with those gauges not working right. If your fuel gauge is working "OK" then its not going to be the regulator / limiter on the back of the instrument cluster! Need to take each lead off of the respective temp or oil psi sender one at a time to see if either may be loading it up. And you'd do well to check the bulkhead connector for water or corrosion that would also cause the problem. I have a similar problem and I know that both my oil and temp senders have worn out, the regulator / limitor is new, and the fuel gauge is working as good as it can. If you still have doubts, get a set of mechanical gauges, they will tell you what is going on 24x7 with out all the hassle of wiring and trouble shooting. Thats what I have done with mine.
 

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A simple test of the voltage limiter from the 77' RC FSM is to hook a voltmeter to your temp sending unit (wire removed) and the other lead to ground. Turn the key on, and if the voltage fluctuates the limiter is funtioning normally. It fluctuates pretty wildly, but it is a really easy way to tell. Last time I bought one at NAPA it was over $40. I hope you get this in time, and I know that I have changed those little buggers without removing the cluster.
 

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Forty bucks for a voltage limiter? That is an extremely high price and far higher than what I found at Autozone. :)

You are correct about being able to remove them without pulling the cluster but it is a tight squeeze.

Ramjet said:
Last time I bought one at NAPA it was over $40. I hope you get this in time, and I know that I have changed those little buggers without removing the cluster.
 

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What Ram said is also very helpful. The gauges in my 1 ton don't work, and the limiter is working fine. The amp gauge works because it has an independent circuit. There is cluster ground somewhere inside the dash that I need to check, but this will require cluster removal. I once noticed that the cig lighter in my 1 ton was not getting constant voltage. After I tightened the cig lighter housing that supplies the ground to that circuit - the gauges worked for about 5 min going down the road. Haven't figured that one out... Hope this helps, and let us know what you found out.
 
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