TEMPERATURE AND GAS GAUGE NOT WORKING-HELP

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chettar

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As the title describes my temperature and gas gauge are not working in my 1963 Plymouth Valiant. Regarding the temperature gauge, I have put a new temp. sending unit in the head, put a NOS temp. gauge in dash, put a new thermostat in, radiator has been reamed and flushed. What else is there? And it still pegs hot on the gauge. I put a radiator cap that reads temp. and it shows 180 as it should with the 180 thermostat. I won't post my problem with the gas gauge but here again I have replaced the sending unit and tested the gas gauge and it shows that it is working but the dash gauge only reads 1/4 tank even when it is full. We have added extra grounds and nothing helps. If someone wants to talk live I am Chet 281-770-2116. I have read everything I can find about these problems and understand about the relationship with voltage regulator but and am about to give up.
 
My money is on the Voltage Regulator... coincidentally I just pulled my gauges out this weekend, but in my case the PC board was burned-out. I soldered a jumper in place to patch it. Haven't yet re-installed.

That is a weird voltage regulator. I'm assuming it's mechanical inside of that metal box. Mine seems to work (according to the factory repair manual). It pulses from 0V to 7V.
 
Here's another vote for RT Engineering's electronic instrument voltage regulator if that turns out to be the problem. The page about how to install it on cars (like the '63 Valiant) that have the IVR built into the fuel gauge is a little hidden; it's here.

However, given that your temp gauge pegs and your fuel gauge doesn't, that suggests the problem is elsewhere: a short to ground somewhere along the wire that runs from the sender (at the top-front of the head) to the gauge.
 
Guys, Many Thanks for the input on my Temp. and Gas gauge problems. I will try your suggestions. Hopefully, this will correct the problems I sure don't want to have to add under the dash gauges.
 
One possible scenario... The mechanical limiter goes bad and sends excessive voltage. The current takes path of least resistance so the fuel gauge is/was the first to toast. If so, zero resistance to ground today couldn't move that needle full swing ( but it wouldn't move fully to home at switch off either ). The excessive voltage is now slowly toasting the temp gauge via the resistance in that sender path. 180 degrees is about 35 ohms where a full tank of fuel is 10 ohms.
Then it could just as easily be totally different conditions. My first step would be,,, Check/prove that the purple temp sender wire isn't shorted to ground somewhere. I've seen it pinched under the slant 6 valve cover, etc...
Then the fuel gauge issue could be the sender ( It has a place where a worn through scrubbing contact will hang like a fish hook ). Or just fuel in the float.
That mechanical limiter is questionable and probably should be replaced no matter what other faults are discovered. Good hunting
 
RedFish thanks for the suggestions, interestingly the first thing that I did was change the fuel sending unit and you are right the float was full of fuel, however the new unit is not sending the correct fuel level to the gauge. I ordered a NOS sending unit but is it possible that they and not balanced to the same ohms or is there another reason that the gauge shows 1/4 tank of gas when I know there is 3/4 or more fuel in the tank?
 
RedFish thanks for the suggestions, interestingly the first thing that I did was change the fuel sending unit and you are right the float was full of fuel, however the new unit is not sending the correct fuel level to the gauge. I ordered a NOS sending unit but is it possible that they and not balanced to the same ohms or is there another reason that the gauge shows 1/4 tank of gas when I know there is 3/4 or more fuel in the tank?
A true NOS sender should make the correct ohms signal. Aftermarket reproduction senders work close enough at full and empty, just way off between. You can access that sender wire behind the left kick panel. Short it to ground briefly and see if that needle travels smooth and quick to 'F', then back to the 'E' again in the same manner when disconnected. Pauses and jumps in needle movement along with less than complete 'E' to 'F' travel are not good signs. If/when you open that fuel gauge to disable the limiter like most recommend, you'll get a look at what makes the needle move ( or not move ).
The thing is... at this point we know most the current coming from your limiter is traveling the temp gauge path of least resistance. Does it make enough current to properly heat up the fuel gauge at the same time? I don't have all the answers, just more questions. Does the temp' gauge go to 'H' when temp' sender is disconnected? Does the fuel gauge function any different when the temp' gauge is inop?
 
A true NOS sender should make the correct ohms signal. Aftermarket reproduction senders work close enough at full and empty, just way off between. You can access that sender wire behind the left kick panel. Short it to ground briefly and see if that needle travels smooth and quick to 'F', then back to the 'E' again in the same manner when disconnected. Pauses and jumps in needle movement along with less than complete 'E' to 'F' travel are not good signs. If/when you open that fuel gauge to disable the limiter like most recommend, you'll get a look at what makes the needle move ( or not move ).
The thing is... at this point we know most the current coming from your limiter is traveling the temp gauge path of least resistance. Does it make enough current to properly heat up the fuel gauge at the same time? I don't have all the answers, just more questions. Does the temp' gauge go to 'H' when temp' sender is disconnected? Does the fuel gauge function any different when the temp' gauge is inop?

Thanks for the additional suggestions, I will resume work on these problems when I return on Monday, Oct. 23rd. Please stay on line with me and I will check out all suggestions and have an opportunity to answer your questions next week.
 
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