Temp gauge "pegs" and "bounces" HELP

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Brad426

Brad426

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Ottawa, Ontario Canada
1969 Valiant

I'm just testing the gauges now and the temp gauge is acting funny. I've tried 2 new sender units to make sure it is not the senders. Double checked the connections & ground.

The fuel guage is not hooked up to the sender unit at this time.
The entire instument cluster was overhauled & detailed profesionaly.

When I turn the key on the temp gauge goes all the way to the right and "bounces". Do you have any ideas?
 
Don't leave it on for long!!! You have a short somewhere. Try removing the nut on the sender stud of the gauge and retesting. "Ohm" the sender connection through the harness. If the sender circuit is open with nothing connected at the sender, the gauge is bad

(It's a simple series circuit----power comes to the cluster from the key, runs to the voltage limiter (cluster must be grounded for it to work right) and power from the VR branches off to the temp/ fuel gauge. If you have a Ralley cluster, the VR is probably IN the fuel gauge, and feeds the oil gauge as well

So the power from the VR goes to the temp ga, through the gauge, and out the sender stud, back up to the harness connector, and to the rear to the tank. One wire.
 
trapster said:
I think your dash regulator is shot
Click to expand...

!!AH!! I misread. Yup, both gauges will show trouble if the VR is bad, so if one is ont hooked up, you cannot go by that

I agree this is probably your no1 suspect.
 
If the panel is dangling from the harness connectors the only ground source would be through the temp gauge sender. The panel must be chassis grounded. A temporary ground can be attached for testing. A perminent dedicated ground wire is recommended.
 
RedFish said:
If the panel is dangling from the harness connectors the only ground source would be through the temp gauge sender. The panel must be chassis grounded. A temporary ground can be attached for testing. A perminent dedicated ground wire is recommended.
Click to expand...

How & where?
 
Just look at the traces on the panel. The grounded lamps, such as signal indicator, high beam, and the "lighting" lamps all blend into one trace. You should be able to hook a pigtail somewhere on this common trace, at a screw. On mine, I scraped some of the coating off part of the trace and soldered a pigtail to it. Then just bolt it to (example) the column support behind the dash.
 
67Dart273 said:
Just look at the traces on the panel. The grounded lamps, such as signal indicator, high beam, and the "lighting" lamps all blend into one trace. You should be able to hook a pigtail somewhere on this common trace, at a screw. On mine, I scraped some of the coating off part of the trace and soldered a pigtail to it. Then just bolt it to (example) the column support behind the dash.
Click to expand...


No you dont ground a trace. The trace is the hot path. Each lamp position should have a ground screw very near it which also attached the circuit board to the housing. You can attach a ground wire to one of or every one of those screws. if you should attach a ground wire to one screw beside a lamp that is a illumination lamp, dont be surprised if that lamp burns brighter than all others. A bunch of screws in pot metal is not a conductor when compared to an actual copper wire.
 
Dads temp gauge isnt reading correctly (doesnt move off of low) so I will be checking this thread out when we get to it.
 
4spdragtop said:
Dads temp gauge isnt reading correctly (doesnt move off of low) so I will be checking this thread out when we get to it.
Click to expand...

That's a different cause/effect. Probably just the sender. Pull the signal wire off the sender, aligator clip it to ground, turn ignition switch on. If pointer races to the max hot position, turn the switch off and replace the sender.
Done.
If the pointer doesn't move, you can try to reach in from underneath and wiggle the gauge by its contact posts. If those nuts are a little loose the wiggle should cause contact a some pointer movement. Then you'll know that the gauge works at least. Then to tighten those 2 nuts would solve that one problem but... The fact that there was a problem in that one suggests potential for other problems that should be addressed.
I've found the best method to the madness is just pull the panel, service the entirity once and be done with it for a very long time.
 
RedFish said:
That's a different cause/effect. Probably just the sender. Pull the signal wire off the sender, aligator clip it to ground, turn ignition switch on. If pointer races to the max hot position, turn the switch off and replace the sender.
Done.
If the pointer doesn't move, you can try to reach in from underneath and wiggle the gauge by its contact posts. If those nuts are a little loose the wiggle should cause contact a some pointer movement. Then you'll know that the gauge works at least. Then to tighten those 2 nuts would solve that one problem but... The fact that there was a problem in that one suggests potential for other problems that should be addressed.
I've found the best method to the madness is just pull the panel, service the entirity once and be done with it for a very long time.
Click to expand...

I spent $1,000 having Mick Maccinie re-build the instrument cluster. Which I trust he did. Yes, you are right. When I disconnect the wire from the sender the gauge goes back to zero. It's the second new sender I have put in and same problem. Does anyone have an idea of what the ohms reading of a stock sender unit should be at average room temp? Or how to test the sender? Tanks
 
Brad426 said:
I spent $1,000 having Mick Maccinie re-build the instrument cluster. Which I trust he did. Yes, you are right. When I disconnect the wire from the sender the gauge goes back to zero. It's the second new sender I have put in and same problem. Does anyone have an idea of what the ohms reading of a stock sender unit should be at average room temp? Or how to test the sender? Tanks
Click to expand...

That post was actually for Steve 4spdragtop.
The sender itself should show 80 or more ohms at room temp.
Stoopid questions maybe but have to ask..
Are you certain you are installing the correct sender for a gauge and not a warning lamp sender ?
Are you sure the gauges are in the correct positions in the panel ?
Are the harness connectors to the panel attached properly.
I've seen some odd errors, temp gauge where the oil gauge should be, etc..
 
Thanks redfish & yes to all.

I hooked up the ohm meter to the sender unit and dropped a temp gauge in the rad. Attached are the results. I'm goimng back to triple check the wires & connections. If they check out it must be the dash VR or the guage. Stand-by

:banghead::banghead::banghead::banghead::banghead::banghead::banghead::banghead::banghead::banghead::banghead::banghead:
 

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Brad I can't figure if you are showing (at 180, say)

25 ohms, or .025 ohms

If 25, it's not far off. If .025, the sender is shorted

A warning lamp sender should be open (infinite) until it gets "dangerously warm" at which time it should be closed (close to zero)

So, you're saying that with the engine warmed up some, the gauge is still pegged?
 
The readings were on the 2K scale. So this is 25 ohms. I have a temp gauge, not warning light. The gauge pegs all the time. I'm gping to back & check the wire from the sender unit to the dash for a short. Stank-by.
 
OK readings should be more accurate (cant read the photo) on the 200 scale or whatever is between 2K and the diode check

If the cluster is hanging free, make sure it's grounded, or the instrument regulator won't work correctly

You should be able to just pull the cluster connector and check the sender wire that way
 
67Dart273 said:
OK readings should be more accurate (cant read the photo) on the 200 scale or whatever is between 2K and the diode check

If the cluster is hanging free, make sure it's grounded, or the instrument regulator won't work correctly

You should be able to just pull the cluster connector and check the sender wire that way
Click to expand...

AH! The cluster was hanging,,,DUH! Back to the shop!:prayer:
 
OK today I screwed the instrument cluster to the dash frame. I think I'mon the right track. I turned te key on and connected the sender unit. The needle does not bounce or peg. Shure would be nice start the engine and see but, the brand new $400.00 Fuelab electric fuel pump internaly digested it's self. &#@*^$%#$. Where I bought it said they would be happy to sell me a new pump. Turns out I have to ship it back to Fuelab for warrentee................So Ihave two weeks to fix other things

For Sale cheap one 1969 Valiant....
 
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