Temp gauge goes crazy when truck is put in park

[Zappafan]

Hey all
We I sold the 1990 and I'm now driving the 72. Thought I had i roadworthy but I'm finding a few electrical issues. The forst is when I put it into park the temp gauge goes wacky and then settles. I also noticed that my tach stopped working when turned on the lights but then it started to work. I noticed that if I shake the shifter lever te tach would work and then not work. I need to replace the circuit board for my tach dash, is there a vendor on the site. I'll be checking thins out after the parade. Happy Canada day.

[69GMCLonghorn]

LMC Truck has the circuit boards. I replaced mine a couple years ago. If that doesn't do it, you need to start tracing wires, one by one until you find the culprit. I'd rather throw a rod than have to track down an electrical problem!! They can be either really simple or a pain in the ...!! Good luck!

[68C10withA396]

The gages in my 68 do some funky stuff too. When I use the turn signals my gas gage drop 1/4 tank. When the head lights are on it goes all the way to empty??? I'd rather not trace wires so I just don't worry about it.

[69GMCLonghorn]

Originally Posted by 68C10withA396

The gages in my 68 do some funky stuff too. When I use the turn signals my gas gage drop 1/4 tank. When the head lights are on it goes all the way to empty??? I'd rather not trace wires so I just don't worry about it.

I feel sorry for people with classic vehicles that have no problems... What the hell fun is that? If everything on my truck worked like it should, I'd sell it and buy something else! I like having a vehicle that not just anybody can jump in and drive without a little instruction... Such as:

Don't use first; it's non-synchro...
Don't try to stop it like a new truck or you'll kill someone...
The horn doesn't work so just yell out the window if someone's about to hit you...
It sucks gas like a 10 cent whore on Nickel NIght, so when you hit a 1/4 tank, FILL 'ER UP!!

I love my truck!!!

[Longhorn Man]

To the original poster...
Look under the hood, towards the firewall, at the bottom of the steering column. Look to see if there is a green wire (that goes to the temp. sensor) and see if it is getting pinched.

To 68C10... you need to make a ground wire and ground your inst panel.

This stuff is easy. Take a couple hrs to actually try to learn how simple electrical systems work, and you'll be amazed at how easy it is.

[Longhorn Man]

There's also a whole forum on this site for electrical problems... which is where this (these) shoulda been posted. There's a couple guys there who know there stuff.

[HuggerCST]

Originally Posted by Zappafan

Hey all
We I sold the 1990 and I'm now driving the 72. Thought I had i roadworthy but I'm finding a few electrical issues. The forst is when I put it into park the temp gauge goes wacky and then settles. I also noticed that my tach stopped working when turned on the lights but then it started to work. I noticed that if I shake the shifter lever te tach would work and then not work. I need to replace the circuit board for my tach dash, is there a vendor on the site. I'll be checking thins out after the parade. Happy Canada day.

I would check the ground wires in this case too. It sounds like you have a bad ground between the cab and frame/engine, and it is making the ground connection through your shift linkage. Check the ground between the cab/frame (Under passenger floor) and the cab to engine at the firewall. One easy way to check this is to use jumper cables or jumper wires between them temporarily. If the problem goes away, add a permanent wire between them.

[Longhorn Man]

I doubt it. He would be complaining about his fuel guage going nuts, and probably comment that he has no dash lights or dome light.... or mention they are working screwy.

[69GMCLonghorn]

LHM, as much as I HATE electrical troubleshooting, you are correct. Once you get in and get over the fear of the unknown, it's usually not that bad, especially on trucks like these.

[HuggerCST]

You may be right, but a bad ground can do funny things, it's easy to eliminate, and I can't think of any other reason for the shifter to have an affect on the tach.

[Zappafan]

Thanks for the advice. I've got it in the shop at work and I'll have a look and see what I can find. The truck sat for many years so there will be lots of stuff to clean up. The whole reason I swapped trucks is to have something I can work on. Had the 3'oclock issue with the fuel gauge and had it fixed in a snap thanks to the many wise people on this site. Okay, I'm off to get some tools and have some fun. Great way to spend Canada Day.

[68 Stepside]

Ground for sure. My 68 did the EXACT same thing. I had no block to firewall grounds. I could wiggle the shifter and actually make the headlights blink on and off, radio would die, etc. Put a wire from the head to the firewall, and perhaps a wire from the head to the frame as well, can't hurt anything.

[68 Stepside]

I almost forgot, my 66 had no grounds either (due to the lack of any cab mounting points....the truck was REALLY rotten). It'd continue to run for a while if you had the heater fan on when you turned the ignition switch off, and when I put a tach in it, it would do all sorts of odd things, like try to die unless you pushed in the clutch a little (I'm assuming that made a good ground to the engine from the firewall or something)

[Zappafan]

I'll be installing a ground strap from the block to the cab, I couldn't find one. I'll see if that cures up some of the problems. Thanks again for the great advice.

[68C10withA396]

This is why I love this forum. I went a and looked to see if there were a ground straped to the fire wall and there wasn't. I could have sworn I put one in there after i dropped the motor in place. Apparently not. I'll add one and see if it does anything different. Thanks all for the advice...
Josh

[Zappafan]

Put the ground strap from the engine to the cab and all seems okay now. The turn signals work the way they should, temp gauge doesn't go all goofy when I put it in park etc. My voltage gauge doesn't work but that could be the curcuit board, it didn't look real good when I put the tach dash in. Thanks for all the ideas and advice.

[leddzepp]

I had some small problems with my dash cluster not working properly. Grounding it properly and adding a cab/frame ground solved most of the problems.

The other problem that it did not solve turned out to be a ground issue within the cluster. I got all of the gauges working in the cluster except the temp/amp gauges. Since I had just restored the dash cluster, I figured that I got too much paint on the backing plate that these two gauges were mounted on, and that it was not grounding to the rest of the panel. I pulled it off, scuffed the edges a bit and the problem was solved. Hope this helps someone else!

[68 Stepside]

Check the small fuses for the amp gauge if it's not working. There's one located over by the battery, and another on the driver's side of the truck, in about the same spot. They're short glass fuses, in a push-together type holder.