dash wiring rookie!

[70xlt]

I did rebuild and posted this question b4. 1970 F100 XLT, I can't get the gas gauge, interior light off and heater fan to work properly or at all. Replaced wiring circuit board, new door jamb switches, I think I checked all the grounds and went junk yard to replace the fuel tank gauge. The fuel gauge is the most important, it worked off and on for while but none now, interior light will not go off, the heater seems to have different power feed to it cause when bypass the fan works, am radio not hooked up. I have the fuel cell ground wire and the 2 wires on steering column on clean paint free grounds, are there any other grounds I'm forgetting? I used tester to make sure I have power to the cell and interior lamp. I'm a senior rookie and have no clue how to repair. I think I've checked all the wires visible for breaks etc. Any suggestion would be appreciated.


thanks 70XLT

[basketcase0302]

="70xlt"I did rebuild and posted this question b4. 1970 F100 XLT, I can't get the gas gauge, interior light off and heater fan to work properly or at all. Replaced wiring circuit board, new door jamb switches, I think I checked all the grounds and went junk yard to replace the fuel tank gauge. The fuel gauge is the most important, it worked off and on for while but none now, interior light will not go off, the heater seems to have different power feed to it cause when bypass the fan works, am radio not hooked up. I have the fuel cell ground wire and the 2 wires on steering column on clean paint free grounds, are there any other grounds I'm forgetting? I used tester to make sure I have power to the cell and interior lamp. I'm a senior rookie and have no clue how to repair. I think I've checked all the wires visible for breaks etc. Any suggestion would be appreciated.
thanks 70XLT

There's a lot here to cover in one reply so let's start with the grounds. You should have no less than 4-5 of them from the factory to keep everything working, (I'm a big fan of "dfedicated" grounds ran to each circuit right from the negatiove on the batter post-I did it using a "terminal block"-as this completely eliminates ALL doubt about ground issues causing electrical gremlins).
1) Main negative post on battery to the engine block (bolted solidly).
2) Engine intake manifold to the firewall of the body, (this is a braided "strap" from the factory and usually has been removed by "hackjob" mechanics) but can easily be replaced by making one using a good #10 thhn wire with two eyelet terminal eneds.
3) Front PS frame rail to the body radiator core support, (another one that is usually "degraded" over the years of being rusted).
4) Steering colum "rag joint" ground strap, (this is a small strap that goes from the steering column coming out of the truck and ties into the steering shaft coming out of the steering box-usually a short braided strap).
5) Know I'm missing another major one here, maybe Randy or someone else can help and chime in here please?!

[390FE1972]

There is a braided ground from the valence panel on the front going to the bumper/frame. I believe this was mentioned, but there is a ground for the wiring harness to the steering column support, and the gas tank sending unit wire to the back of the cab. Here is the 1970 wiring diagram that shows some other grounds: http://www.fordification.com/tech/wirin ... master.jpg Click on it to enlarge it.


Regards

[sargentrs]

This is on the 1972 full master wiring diagram.
http://www.fordification.com/tech/wiring_1972master.htm

[basketcase0302]

Some troubleshooting you can try without using a voltage meter. But I'd highly reccomend getting familiar with how to read a digital multimeter as there are a lot...of things on our truck you have to be able to do that to troubleshoot.
So in addition to the grounds issue you still have:
1) non working gas gauge.
Try grounding the sending unit wire/pull it off the sending unit and touch it to ground/did this make the gas guage go up at all?
http://www.fordification.com/tech/fuel- ... -units.htm

2) Interior light staying on constantly.
This is almost always gonna be the crappy OEM "pin switches" in the door jamb. Try pulling one switch out at a time to troubleshoot. It could also be in the headlight switch itself, (which you turn all the way to the left to turn the inside lights on) as that part of the switch could be "welded" (contact wise) as I've seenn in the past. Try unplugging the heaqdlight switch harness to see if it turns the inside light off.
Don't let the master wiring diagram intimidate you as we'll go through it one wire at a time if need be:
http://www.fordification.com/tech/wirin ... master.jpg

3)Your heater works in "bypass" (I'm guessyou mean when you hook a hot wore to it the fam motor spins right? If that's the case there are only two other things it could be, (if it is properly grounded inside the cab to the metal housing). The same master diagram above will help you troubleshoot the blower motor resister, (which fails from time to time) of the blower switch (which is more than likely the culprit).

[70xlt]

THANKS! All my lights work except interior cab, (they stayed on all the time) I have new terminals in the door jamb and waiting on light bulb to see if repaired. The heater works now due to fuse panel socket. During rebuild I put new braided harness from the motor to the firewall, It has 2 grounds on frame behind dash at steering column frame which I re cleaned, I rechecked the grounds behind the seat at the gas tank. In rebuild I put new circuit board on back of dash panel. I don't remember any grounds at radiator or anywhere else during tear down b4 restoration. I did rebuild rag joint during restoration. I just bought wire tracer to see if line broke between tank and dash, just put 3rd dash voltage regulator on it plus new gas tank sending unit. On initial crank the gas gauge worked plus the DC gauge but 2nd try it's now not working, is something blowing the voltage regulator? I'm stumped and don't know where to look. I'm going to reread the post and try rechecking all again. Please suggest anything.

The only things not working are the gauges (fuel, voltage). I have auto meter for oil, water that are working, the dash lights works too.

thanks a bunch for being patient with the senior
70XLT

[70xlt]

Hey, thanks for the wiring diagram but I don't understand how to read them, what is the ground sign I'm looking for on the diagram?

[sargentrs]

It's the 3 horizontal lines of descending length. This shows the ones on the parking light. One near the housing and the one that's the bulb socket. Diagrams get easier to read with practice. Start with an area you're familiar with, like the fuel tank sending unit, and follow the diagram while you follow the wires. It'll start to make sense to you then.

[70xlt]

I disconnected the original oil and water temp gauges and installed new equipment from senderS back to auto meter gauges. I left the original water and oil temp wires in the wiring loom on the engine intake. I’m almost positive they are not touching any metal but... could this be causing the instrument voltage regulator to overheat on initial power to it. I’ve tested the battery with tester and it shows no short with switches, lights etc in off position.

Thanks for being patient with this old guy
70 XLT

[sargentrs]

I replied to your email. But for everybody else, I'll post it here too.

Take a look at the attached snapshot of the instrument cluster and the harness connector. There is supposed to be ground at wire #57. Looking at the diagram you kind of flip the plug over on top of the cluster to line up the connections. It's like you were holding the plug in your left hand, looking at the bottom side, not the wire side, and had the cluster laying on it's face on the right side, looking at the socket where the plug goes in. Wire socket #57 is the ground to the all the dash lights. If that's not connected well, you could be getting a short there.

InstrumentClusterGround.JPG

Not really sure but I think this may be ground referenced in the diagram. Never paid that much attention.

InstrumentPanelWiring.JPG

[basketcase0302]

Randy.
We don't see this too often, (ground issue with the panel) but it had stumped me once or twice till i accidentally touched the metal housing to the cab (making a ground) and the gauges went up.
Never knew that was where it got it's ground!

[sargentrs]

Me neither Jeff! Not til this thread and was looking at the diagrams. I always thought they grounded through the mounting screws. I've pulled my cluster several times and don't ever remember that ground wire.