Deuce gauges have gone loco!

[Woodsplinter]

About 2 months ago I replaced all the gauges on my A2 deuce with new ones and I also replaced the temp and oil pressure sending units. All gauges have worked fine since then.

About 2 weeks ago I parked it and did not drive or work on it for 2 weeks. I went out to start it and it started up right away, like it always does. All the gauges looked fine initially. After several seconds the fuel gauge went all the way over to FULL. I know the tank is only half full. (Verified by "the stick")
The oil pressure gauge then started jumping all over the place- over to full pressure, then back to 0, to 3/4, and on and on. Finally settled on 10 psi, then dropped to 0.
Engine temp was fine, so based on the erratic pressure gauge I went to fill the tank to see what, if anything that would do to the fuel reading. After filling the tank the needle pegged itself on the FULL side, now reading higher that it had earlier.
I drove home and engine temp remained below 200. (Normal)
Oil pressure gauge continues to bounce around.

I checked all the grounds for the gauges and they are fine. All lights work fine- no other electrical problems. Batteries are full of water and the terminals were just cleaned recently. Battery cables look fine.

All other gauges are working normally so I'm baffled about this.

Does anybody have any idea what might be wrong or what I should check next?

Thanks guys!

 

[steelandcanvas]

I'm thinking it's probably a grounding issue. Make sure the instrument panel is making good electrical contact with the rest of the dash area. If need be, run a separate grounding wire from the panel to the dash. The four screws in the panel get dirty and lose their conductivity to the dash. Hope this helps.

 

[Woodsplinter]

Steel, thanks that's a great idea. I will try adding a ground wire in the AM. I was thinking the other gauges would also be affected by a bad ground- or not.

I'm finding that some of the equipment on these trucks is just plain "wonky"!

Mark

 

[steelandcanvas]

Steel, thanks that's a great idea. I will try adding a ground wire in the AM. I was thinking the other gauges would also be affected by a bad ground- or not.
I'm finding that some of the equipment on these trucks is just plain "wonky"!
Mark

I'd try that first and then go from there. It could be some other issues, let's start with the simplist first.

 

[Woodsplinter]

I agree with your approach- just wasn't sure what to do next.
I'll check that and keep everybody posted.

 

[Woodsplinter]

Well, I started the deuce today and noticed the fuel gauge seems to be reading correctly now. The oil pressure is still weird. I connected a ground wire directly to the oil pressure gauge and to the dash and no change. I'm wondering if the sending unit or gauge has gone bad prematurely.
Anybody know a simple way to test them?

 

[pyro1955]

Did you connect the ground directly to the engine or battery ground, or is it connected to the gauge to the dash, it could be your chassis ground is the culprit. Just a guess as luckily I have not had these issues with my Deuce yet, but I have done alot of wiring building Limo's in a past life.

 

[Woodsplinter]

Actually I connected the wire from the mounting post of the gauge to a bolt attached to the dash. (Not the removable instrument panel). I can't imagine the entire dash is ungrounded but stranger things have happened.
I'll repeat the test going from the gauge to the battery and see what happens.

 

[steelandcanvas]

I'm wondering if the sending unit or gauge has gone bad prematurely.
Anybody know a simple way to test them?

I don't have the resource right in front of me, but I believe there is a drawing and text for troubleshooting gauges in the TM, you might have to dig around a bit to find it. I wish I could give you a page and diagram number.

 

[Woodsplinter]

Ok, I'll start hunting for it. Connected a ground wire directly to the battery from the gauge but that didn't help.
Doesn't look like the ground is the issue.

 

[rrrr]

I had to replace the temp gauge because it would just stick. No problems since. You might want to pull the pressure sender and make sure its clean. Then maybe a gauge replacement.

 

[Woodsplinter]

Yeah, that sounds like a good next step- I'll pull it and check it.
Gotta do some honey-dews first...

 

[Woodsplinter]

Well, went through the troubleshooting procedure on the TM's and that indicated the gauge is bad.
Gotta get another one to see if that's it.

 

[whatadeuce]

Hello everyone, and I have been following these posta. may I ask: is there polarity with these guages? Peter Mark

 

[Woodsplinter]

Peter,
The gauges are all negative ground. They are usually grounded to the vehicle through the body of the gauge or the mounting bolts.

 

[whatadeuce]

Thank You Woodslitter, and does it matter that the wires be re connected to the same teremimals? If I switch them by mistake will this reverse the guage? Peter Mark

 

[Woodsplinter]

Yes you need to reconnect the wires to the same terminals. Don't know what will happen if you reverse theml
Mark

 

[whatadeuce]

Well I thought I rerconnected the correctly; so I shall reverse them and see if the "new" gaugw works then. I am not sure of this type connector iether, but as I have pulled them apart and put them back together again, I can better recognize if I am making a good connection...To be continued tomorrow ...Peter Mark

 

[Woodsplinter]

Check out the wiring diagram in TM 9-2320-361-20, page 4-19.
That may help you out.

 

[whatadeuce]

Thanks Woodsplitter, I will do just that. Peter Mark