Trouble with gauges

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Kannon Herbert

Kannon Herbert

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Alright, this problem has been plaguing me for weeks now. I have a 1974 Dodge Dart custom. My gas and temperature gauge do not work. I started by taking apart the cluster, checking the gauges for functionality, and fortunately they work. I decided to replace the IVR while I had the dash apart. Still not working. Next I tested the temperature sender. It works correctly and has the correct resistance. I then checked that all connections all the way to the cluster pins were solid from the temperature sender, and they were. I’ve recently tried hot lining the top pin on the cluster, which heads to the idiot lights, and the IVR and in turn the temperature and gas gauges. When I hotline the gauges they work but I have to disconnect the battery before the gauges are pinned and will ultimately fry. Is the top pin on the back of the gauge which is labeled as (a) a supply for power? Or what am I missing. I just am not sure where to go from here. One thing to note. I’m missing a bulb socket for the brake light on the cluster, could this be causing serious issues with the total circuitry? I’d think not, but I’ve been told these clusters are complete systems and that one small problem can ruin the darn thing. Thanks for any help. I’m just stumped.
 
Have you made a good ground from the cluster? Seems improbable if the dash lights work propperly.
Check the rear posts on the guages, with power to the cluster you should see voltage to ground on one or both
 
Look at the wiring diagrams and several pages back behind them there are diagrams of the connectors.

pcconnector.jpg


Now you have to fiddle with the diagrams and figure out power. I'd guess one or other of the dark blues , G4 or G5 Notice this connector is labeled CI-10 see below
 
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So now we end up on page 8-157 here is a partial shot

cluster.jpg


Notice down near the IVR the connector is CI-10 which means Connector, Interior no. 10 and the wire there is G5-20DBL which is wire G5, it is 20 gauge, and is Dark BLue that is the power to the IVR from the ignition switch
 
Things to check for

1...Find a common ground point such as the ground side of the dash lighting which is connected to anything else on the board that is ground. Somewhere in that ground plane is one or more mounting screws. Connect a pigtail to that and bolt it to either the dash frame or the column support

2....Check the harness connector pins for looseness to the board traces and clean and solder them as necessary

3....The contact fingers for the IVR can loose contact with board traces. Solder jumpers across between the board traces and the contacts

4....The gauge studs can lose contact with the board traces. Loosen/ tighten the stud nuts several times to "scrub" the connection and consider replacing the "fake" nuts with real ones

5....Obtain a way to provide test resistances for the senders. If you have a rheostat or old tank sender you can set that. Provide 12V to the proper pin we were just discussing, and apply a test resistance to the gauge sender connection Each guage should read to proper point depending on resistance
 
These are the resistances I can't take credit some soul photoshopped the resistances into this photo of a guage tester

c-3826-jpg-jpg.jpg
 
Kannon Herbert said:
A I’m missing a bulb socket for the brake light on the cluster, could this be causing serious issues with the total circuitry? I’d think not, but I’ve been told these clusters are complete systems and that one small problem can ruin the darn thing. Thanks for any help. I’m just stumped.
Click to expand...

No. The brake warning light is not grounded, and should not affect other circuits. The way it works is that there is a grounding switch on the parking brake, and a grounding switch on the brake warning pressure switch. Both these are connected together and to one end of the lamp. the other end goes to switched ignition 12V so that if the parking brake is "on" the switch grounds and completes that circuit
 
67Dart273 said:
No. The brake warning light is not grounded, and should not affect other circuits. The way it works is that there is a grounding switch on the parking brake, and a grounding switch on the brake warning pressure switch. Both these are connected together and to one end of the lamp. the other end goes to switched ignition 12V so that if the parking brake is "on" the switch grounds and completes that circuit
Click to expand...
Thank you so much for all this information, it’s going to make a big difference when I go to tackle this tomorrow. I seriously appreciate it.
 
Kannon Herbert said:
I’ve also noticed that 20dbl isn’t getting any power in any key turn position.
Click to expand...
G5 20dbl has to supply 12 volts to the limiter, the brake warning lamp, and oil warning lamp, with ign' switch in run position,,, so that is your problem. You'll need to trace G5 back to its source. I don't know if this is fused in the later models but I know it wasn't fused in earlier models.
As for the 'A' and 'S' on the back of your fuel and temp gauges, 'A' is altered or adjusted voltage in, 'S' is sender or signal. when testing gauges outside of the panel with a 3 to 5 volt power supply, which is which wouldn't matter. Current from post to post generates heat, heat bows the bi metal beam. That beam wouldn't bow backward with reversed polarity.
 
I had a similiar issue. Gas & temo gauges not working after swapping faulty speedometer! They worked before. So took cluster out like 3 times and no luck. So ordered the solud state IVR from ebay. RT engineering makes it. And just reinstalled it and all was good again!
 
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