temp and fuel gauges inop??
 

So i have an issue with the temp and fuel gauge. the sender pegs to e when hooked up and to f when unhooked. The temp gauge doesnt work at all. someone has removed the wire going to the temp sensor all together. My Question is there are 4 different bolts coming off the back of the temp sensor , which one do i hook the gauge up to the sender ?

Re: temp and fuel gauges inop??
 

Re: The fuel gauge, that behavior sounds like it is wired properly. If you believe the "E" reading to be incorrect, it may be that something happened to the float on your sending unit (which is pretty common I gather), or your unit is bad.

I don't know about your temp sensor question, mine is just a single wire to a sensor with only the single connection on the drivers side of the engine.

Re: temp and fuel gauges inop??
 

can u snap a pic of the back of the temp where the wire is hooked up i see two bolts where its connected to the circuit board , but there are 2 studs on the back additionally. is that where the wire goes

Re: temp and fuel gauges inop??
 

For the temp gauge, you shouldn't need to connect a wire to the back of the gauge itself. The wire connects from the harness to the plug in for the entire cluster. As long as your circuit board is all good, that probably isn't the problem. If you look at the wires coming out of the firewall on the engine side, you'll want to find a green wire. That's the correct color for the temp sending unit. Start there first. Someone had cut that wire on mine and I had splice in a new wire and bring it to the temp sending unit.

Re: temp and fuel gauges inop??
 

Any time you post a question you should include a little information about your truck, like year, engine size, etc. Many times that will make a difference in the responses you get. There are no wires that connect directly to the gauges, everything goes through the printed circuit board. If the Dark Green wire has been removed in the engine bay there would still have to be a terminal at the bulkhead connector on the firewall for it. Someone may have folded the Dark Green temp wire up and stuck it in the plastic wire channel at the top of the firewall. In the picture below follow the 20DG wire from the Temp switch to the firewall connector and see if you have a wire in that position. If so, it needs to be connected to the temp switch.

Re: temp and fuel gauges inop??
 

I appreciate the quick response, and i will check furhter up the wire harness on the firewall for the green wire. Sorry btw for lack of info . It is a early 1970 (11/69 ) chevy cst10 with a 350

Re: temp and fuel gauges inop??
 

The fuel gauge sender wire may be grounded if it always shows empty or the float may have gas in it and be to heavy to rise. your gauge is doing what it should based on the readings. Take the sender wire off at the sender and if it still reads empty then the wires is shorted to ground. This happens a lot when the wires run under the drivers door sill plate.

Here's a pic of the temp gauge wiring. The bottom post must be grounded to the dash cluster. and the cluster itself must be well grounded to the cab.I would guess that it is because the gas gauge is responding to the inputs.

Attachment 1813600


Here is a diagram of the gauge cluster wiring. The no.3 terminal on the cluster plug comes from the fuse panel, and feeds the gas gauge positive side, which also feeds the positive side of the temperature gauge. The no. 4 terminal on the cluster plug is where the sending wire for the fuel gauge connects.
The no. 6 terminal is where the green wire for the temp gauge sender goes. in case you can't find the green temp sender wire you could run a new wire from the no. 6 terminal to the temp sender. If you want to check the temp gauge you can ground the no.6 terminal on the plug and the gauge should go to full hot.

Here's a diagram of the gauge cluster wiring.

Attachment 1813598

Re: temp and fuel gauges inop??
 

great advise , probably your fuel sender is bad in the tank , replace it they are cheep , there is a brown wire going to it

Re: temp and fuel gauges inop??
 

working on the fuel gauge now. I already replaced the wire from the sender to the fuse block. it pegs empty and reads full when unhooked .im gunna try the sender next. this truck was a wiring nightmare . it was a rats nest under the dash i am slowly fixing the electrical gremlins atm. just found out the alternator isn't charging the battery , which would explain my starter issues . It would really help tho if the wire to feed the voltage regulator was hooked up to the battery. I need to go thru a wire diagram to find the missing wire. The temp gauge is fixed now tho .Thanks to the supplied wire diagram , i found the green wire hanging out with the transmission pretty much touching the ground.

Re: temp and fuel gauges inop??
 

Here is a little bigger diagram that Locdoc posted that shows the charging wires.
They join together in a soldered connection inside the harness behind the left headlight.





Attachment 1815955


The circled fuses are for the battery gauge in the dash and the arrow points to the shunt wire that runs across the top of the radiator which carries battery current to the truck when the engine is off. It also carries current from the alternator battery voltage regulator junction back to the battery to charge it when it gets low.

Re: temp and fuel gauges inop??
 

so i found last night that everything is hooked up . im going to try the voltage regulator see if this takes care of it . the battery gauge does work on the cluster tho. it always just went up to the halfway mark so i assumed it was charging

Re: temp and fuel gauges inop??
 

You can tes the regulator for voltage by checking the brown wire on the end terminal for 12 volts with the key on and zero with the key off. Then check the white wire on the alternator for the same results. The blue wire on the alternator should have 12 volts with the key on or off.
If you get those readings then you can fire the engine up and test the alternator output for 13 plus volts at idle and no more than 15 volts at 2k rpm.

Re: temp and fuel gauges inop??
 

so update ; so far i have done the following:
* replaced battery
* replaced both voltage regulator and alternator
* replaced both fuses in the harness
* checked for continuity (which it has) in between junction connector where it splits at red wire (by firewall) and on the other side of the red wire where it comes out from the fender . at this point im not sure where to go ?????HELP

Re: temp and fuel gauges inop??
 

Brown wire is putting out 6 volts koeo, white no voltage at all , blue none at all either. Red nothing also

Re: temp and fuel gauges inop??
 

The red wires for the alternator, Regulator, battery, and the key switch all come from the soldered junction in the wiring harness. If you have no voltage on the red wire at the regulator or the firewall plug then you need to check the positive terminal on the battery and the junction on the right fender for voltage. There is supposed to be a small fusible link wire from the battery positive post to the right fender junction as shown on the diagram I posted above, and if it is missing or blown you won't get any power to the alternator, regulator, or to the cab.

Re: temp and fuel gauges inop??
 

Finally figured out the problem!!! the red wire going into the voltage regulator was severed in the harness. re-solderer the wire and BAM!!!!!!!!! charging again ,and the starter no longer has issue. I want to thank everyone who has helped me with this nuisance of a problem. This is probably one of the most insightful forums ive ever been on. So thank you everyone for the great experience !!!!!!

Re: temp and fuel gauges inop??
 

Glad you finally got it figured out. That would be a tough one to catch....

LockDoc