NEED help, nothing working on my dash...

[Uncle Don]

ok happy endings are done. update:

got everything back together...well other than ac/heater stuff but that can wait. i got dash lights working, that was light switch. turn signals work, voltage gauge works, radio works...put a new voltage regulator on it and still no *&^% *&^$$#% temperature gauge or fuel gauge working!!! what gives? i grounded the temp gauge to check and i cant get the needle to move on the gauge or anything....doesn't do a thing when grounded and turn the key on either.

help. ive got after market gauges but really wanted the factories working....

 

[68ChargerAG]

Verify that you have voltage at the back of each gauge. If you don't, you need to trace back to the inst panel voltage regulator to see where it is broken. If you have voltage at one post and not the other with everything plugged in, the gauge probably is bad, if you have voltage at both posts the sensor or wire to the sensor is probably the problem.

Here is my understanding of how the system works. The voltage regulator controls the incoming voltage which then goes through each gauge and on to each sensor (or sending unit). The sensors each have variable resistors in them, the gauges respond to the varying current flow through them based on the given resistance in each gauge at a given time. In order for the sensors to work the body of each must be grounded. I have read that it is not a good idea to ever ground the sensor voltage as it can cause over current through the gauge and burn them out, but you do need to ensure that the body of each sensor is grounded.

The fuel gauge has a gasket on it so the body does not touch the gas tank and so is not grounded to the gas tank. You need to verify that the little strap with clips on each end is clipped on to the gas line on both sides of the rubber flex hose back at the tank. If it is lose or corroded it might not be working. The strap grounds the sensor to the car's gas line which is grounded to the car... so it must be in place for the gauge to work.

The temp sending unit can easily be replaced if you think it is bad, I don't think that they are very expensive.

I hope this all helps, good luck.

 

[CjVan]

The fuel level gauge needs that little clip that goes from the sending unit output tube to the gas line across the flexible line connection to ensure it is grounded, if that is missing the sending unit will not work.

I think thats the problem Im having... The little clip is there but the fuel line isnt factory, its a hard metal line that screws connects to the electric fuel pump under the passenger door (67 BII) where it then turns into a rubber line that goes to the carb... So im assuming i have not enough ground, will there be enough if i wire the ground clip to the underside of the body near the gas tank?

 

[68383GTS]

When you get it all working the tail lights and side markers quit in my 68 GTS for no reason.LOL

 

[68ChargerAG]

will there be enough if i wire the ground clip to the underside of the body near the gas tank?

If you can rig up a wire that grounds that clip directly to the car chassis you will be set. Just make sure that you have good contacts at both ends of your wire and the clip does not fit loosely to the gas line on the sending unit output. I have noticed that the clip can get corroded and loose, so just make sure the connection is secure.

 

[74 Bluerunner]

same problem, no power?

If you are not connected to your alternator (ammeter) gauge you will not have power to anything in the car unless the gauge is bypassed. The power that goes to fuse box and everything inside the car goes through the gauge first so if it is disconnected and not bypassed you won't see power at your fuse box.

Do you have 12.4V on either of the two fat wires that connect to the alternator gauge? If not, trace the one back through the firewall that connects to the pos terminal of the starter relay, that one should cary your 12V from the battery to inside the car. If you do have power on one of them, short the two together ( thus bypassing the alternator gauge) and you will have power to your fuse box etc.

I have power on one of the starter terminals (top) but not on the bottom wire. Is that a fuseable link problem? Pulling 74 roadrunner into garage last night and boom.. no power-no headlights, dome light, absolutely dead. chckd battery ground. ok.. top wire to starter terminal is hot but not bottom.

 

[70rr-brian]

I will drop some pretty obscure knowledge here regarding your temp/fuel guage problem. I had a similar issue on my 70 RR rally dash. Turns out...the 5 or 6 pin connector on the back of the dash assembly located just above the wiper switch and more centered to the assembly had a busted pin. As you look at the back of the assembly, the 2nd pin from the right had become so loose it wasn't making contact. In fact, it eventually just just stuck in the connector.

As embarrassing as this is to say... I tried soldering it only to have it pop back off. I eventually ended up tapping a finishing nail into the hole and mounting the pin on the nail then soldering it down to keep it from pulling out. That solved the problem.

Not saying that is your problem. But that second pin, if loose or not making a good connection will in fact only affect the temp and gas gauge. Just make sure it is making solid contact by using a continuity tester.

I sincerly doubt that the answer lies in trying to fix each gauge individually. But then I am often wrong.