Under Dash Wiring

You're absolutely right about the Cnhiropractor (and beer). Even taking out the passenger seat and bracket, then dropping the heater control out of the way, it's a contortionists nightmare. Slow and steady is the way I'm going, but nothing obvious yet. I'll get back to it tomorrow. Not sure if I'm ready to take out the entire dash board.

 

Visually all the wires look pretty good under the dash and hood. No missing grommets as they pass through the firewall. So far, so good.

I've got the ohmmeter set up and started looking for grounds that shouldn't be there. First checked the gauge cluster and found some odd stuff. Is the strap between the fuel and temp gauge supposed to be grounded? Zero resistance between it and the dash, according to the meter. And the post on the fuel gauge for the green wire going to the ignition is also grounded. So, that seems wrong. It also has a purple wire that seems to go to the oil light and light grey that goes to the batt light. The other posts on the two gauges are showing resistance, which I guess is good.

Thoughts?

 

Proceed with caution. The gauges incorporate an internal voltage regualtor, and if it is not grounded it can be burnt out, permanently.

Search here for much discussion and explanations.

 

NO..It should have a resistance reading of 49 to 51 ohms if the strap is removed from the "A" term on the fuel gauge. Remove the wire from the "S" terminal on the Temp gauge and connect the strap from temp to fuel gauge. Measure the resistance from the temp gauge "S" terminal to speedo housing ground. Your reading should be a total of temp S to A 19-21 ohms plus fuel A to ground 49-51 ohms for a total of about 70 +/- ohms.

 

Thanks, good advice.

i think I've found the mysterious ground. When I disconnect the strap between the fuel and temp gauge I found the A post on the fuel gauge is showing ground. So I guess that means it's somehow internally grounding to the gauge cluster case?

I'd rather not tear the case apart myself, so I found an electrical guy who can check it out. The question is; can I drive with the strap between the fuel and temp disconnected without damaging something? He's not far, so I can tow it, but I'd rather drive.

Thanks!

 

Yes, the cardboard is there and in good shape. But... I noticed the fuel gauge moved slightly when I went to check the tightness of the nuts. So I gave a little wiggle to move the gauge up very slightly and NO MORE GROUNDING problem. I guess it's inside, so maybe I really do need to take out the whole cluster, carefully take it apart and look it over.

Having a Jeep (and lots of knowledgeable helpers!) sure is a learning experience. Of course the learning will continue.

Thanks!

 

The looseness of the fuel gauge is what smokes more than one of them. There are a couple a dimples in the housing which is supposed to help align the fuel and temp gauges to their proper orientation. This also serves to keep the posts from touching the housing and shorting out the gauges. The proper alignment is critical. If you remove that back cardboard (hold the gauge in place) and you can see how close the posts are to the speedo housing. If you don't want to do this yourself you can remove the wire from the "I" terminal in the fuel gauge and drive your jeep to the tech. Be sure to tape over the end of the wire as it becomes hot with ignition on.

 

Once you fix the gauge, post up the procedure. I only have three that need attention now.

 

It's off to the wiring guy today, so let's see what he comes up with. I'll keep you posted.

 

The good news is that I finally have a working fuel gauge for the first time since I've owned the CJ5. There is no bad news since the tech opened up the gauge cluster and said everything looks in order and is working. Nothing touching grounds that shouldn't be touching. He said the process is straight forward. Remove the cluster, disconnect all the wires and work on it on the bench. That involved replacing the fuel gauge itself and assembling everything and finally reinstalling in the dash.

I'll cross my fingers until the next time...

 

Your lucky you found someone that would even take that repair on. Many of them now will only replace complete components pre-assembled.

 

Believe it or not, he's at the local Jeep dealer. They do antique and classic car restorations as a sideline. While I was there they were finishing up on a 1924 Ford Model T. So my CJ5 was a perfect match for them.

 

Like I said. YOUR LUCKY...

 

Yeah, but the fuel guage on the Ford is a wooden ruler marked in gallons.

It's all been downhill since then.

 

I used to have to lean out the driver's seat, open the gas cap and look into the tank. Awkward, but it worked... Sort of. Not very accurate, though.