My Temp Gauge I Making Me Hot Under The Collar

[dodj]

I checked the voltage, at the tank. You are right, 10.8 non pulsating volts. It would appear my voltage limiter is the culprit? I still don't understand why the other gauges were not pegged, though.

It does appear that way, but the fuel gauge not pegging is mystifying. Oil should peg too, but being a new Redline replacement, can't say for sure.
I'm willing to bet your battery reads 10.8 right now when your key is in the on position?
Looks like you will be removing the cluster after all. Wonder if it's possible to mount the gauge cluster and not get an effective ground? With the mounting screws I can't see failing to get a good ground but it might be worth running a ground wire to your cluster and see if your limiter starts to work? 

[floorit426]

I just got off the phone, with Redline. He looked up my invoice and they did install a solid state voltage limiter. I explained my issue and he said my sending unit wire must be grounding on something. He said they have never had a failure, with their limiters and that, if it did fail, the gauges would just not register any readings. The curious thing about what he said was that I should NOT be getting any voltage readings out of the wire.

[Jay Bee]

he said my sending unit wire must be grounding on something.

If that wire was "grounding on something" you'd read 0v, not 10.8v

He said they have never had a failure, with their limiters

There's always a first time. If it were to blow open then the gauges wouldn't read. If it were to short out, then battery voltage would be present at the gauge.

[floorit426]

I never thought to see what my oil pressure gauge was reading (I suspect it is a converted temp or fuel gauge), so I just checked it. With the engine off, but the key in the "on" position, it doesn't move. This makes me think that the problem is with the temp gauge circuit only, and the instrument cluster is okay? I still don't know why the volts read 10.8. Although it is a Harbor Freight gauge....

[dodj]

I don't think he listened to everything you (probably) told him. A grounded wire/sender is the most likely cause when a single gauge is pegging. However, like JB says, you would have 0v not 10.8v.
The job of the solid state limiter is to 'limit' the output voltage to 5v. Mine puts out a steady 5.03 volts.
There must be an issue with your limiter if it's putting out 10.8v, it's not doing any limiting.  I'm thinking the fault lies in how it is connected, grounded, or it's a faulty limiter.
I'd pull the cluster and verify that it is connected correctly. Did it come with a diagram to indicate 12v and 5v terminals? If it is connected correctly, take it out and test it on the bench.
If it works on the bench, probably a cluster grounding issue.
If it doesn't work, send it back to redline.

[Mopar5]

Regarding the 10.8 volt reading , There are different types of shorts in auto circuits one is short to ground or a dead short ,But you can also have a short to power or a backfeed . You can eliminate the short to power possibility by removing the sending unit from the guage and then checking it for voltage on the sending wire. I doubt that is the case but worth checking. I still think you have a grounded sending wire.

[dodj]

 

[floorit426]

I've been finishing up a couple of projects, around the house that have kept me from digging further into this issue. I'm going to pull the gauge cluster, tomorrow, and have a looksee. Thanks, for the gentle "nudge"!

[floorit426]

Okay, gauge cluster pulled. It appears that my limiter isn't limiting. That explains the pegged temp gauge, while the "lower than actual" gas gauge remains a mystery. The reason the oil pressure gauge is unaffected is that they installed an aftermarket 12 volt unit and it is wired independent of the other gauges.

[floorit426]

Okay, here is the epilogue, to this. I installed a new voltage limiter, and the temp gauge now functions correctly. However, the fuel gauge would not respond. That turned out to be a poor ground. I suspect that the fuel gauge was registering , but not accurately, as a result of having 12 volts sent to it, despite the poor grounding. Anyway, the car is back up and running and will get some road time, today.

The problem turned out to be pretty basic. It just shows what can happen, when you overthink a problem. Thanks, for everyone's input, on this!

[Jay Bee]

It just shows what can happen, when you overthink a problem.

That's one way to look at it BUT it's very easy not to suspect a brand new component (voltage limiter) especially when the supplier says they've never failed and the dash was professionally rebuilt.

Very glad to hear it's all sorted out.

[RUNCHARGER]

It's unfortunate but you just can't trust new parts.