I have no dash lights working in the instrument cluster. So I removed the lights and they still looked like good bulbs. I then replaced the socket without the bulb and tried to test the sockets to see if they were getting electricity. I was not able to detect any however this seems a bit hard to do since their are no direct wires running to the sockets. Anyhow the real problem was when I replaced the instrument cluster and started my car the gas gauge started going all haywire and soon to follow was the temperature gauge. They seem to at first react to the throttle then just max out. Then my battery keeps dying, (perhaps unrelated or due to me not getting a good connection, when I reconnected it after working on the dash).So does this just sound like some bad wires behind the dash and common elec-trickery or something more common? Also I am found of checking if the alternator is working on gas engines by simply removing a battery cable while the car is running. Is their any shortcuts on diesels without relying on a meter?

I don't understand all of your post and I don't know what kind of car is involved but absolutely, positively do not remove the cable from the battery while the car is running. The battery acts as a capacitor to smooth out alternator spikes and running this way can definitely damage some electronics and/or electronic protection systems. On a 40 year old car, maybe (still pretty physically dangerous) but not on a modern car with an OVP, ECU, ICU, ABS, etc.

The simplest way I know to check an alternator is to check the running voltage. It should be 13-14.5 volts, and a $4.00 meter from Harbor Freight has enough accuracy to show this. Anything less, even after charging a dead battery for a few minutes, you have an alternator problem.

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86 560SL
With homebrew first gear start!
85 380SL
Daily Driver Project

http://juliepalooza.8m.com/sl/mercedes.htm

Might help if you told us what car you are talking about.

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1985 Euro 240D 5 spd 140K
1979 240D 5 spd, 40K on engine rebuild
1994 Dodge/Cummins, 5 spd, 121K
1964 Allice Chalmers D15 tractor
2014 Kubota L3800 tractor
1964 VW bug

"Lifes too short to drive a boring car"

Sorry about that guys, was a little flustered with my problems. An 82 300td

The wagon? How clean are all the eletrical connections?

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RRGrassi


70's Southern Pacific #5608 Fairmont A-4 MOW car

13 VW JSW 2.0 TDI 193K, Tuned with DPF and EGR Delete.

91 W124 300D Turbo replaced, Pressure W/G actuator installed. 210K

90 Dodge D250 5.9 Cummins/5 speed. 400K

The usual fault for no instrument cluster lights is the rehostat that controls the intensity of the lighting.
Sounds as if your other problems might be a bad main ground to the cluster. If you can identify a ground point on the back run a temporary ground to check. You also may want to check the fuse but my suspicion is it would have not become erratic if it was just a fuse. Although it could also be out now as a result of whatever is wrong.

Thanks Barry, I will check the ground and rehostat. Sorry not the wagon the sedan.

Then you have an '82 300D.
Live it, learn it, know it........

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Jimmy L.
'05 Acura TL 6MT
2001 ML430 My Spare

Gone:
'95 E300 188K "Batmobile" Texas Unfriendly Black
'85 300TD 235K "The Wagon" Texas Friendly White
'80 240D 154K "China" Scar engine installed
'81 300TD 240K "Smash"
'80 240D 230K "The Squash"
'81 240D 293K"Scar" Rear ended harder than Elton John

Yes an 82 300d but it is a turbodiesel so I wasn't quite shure if I should throw a t in front of the d. Or is this car refered to as a 82 300d with or without the turbo? And beleive me I am learning it. Installed a new rearend, swaped dashes, new shocks, new tie rod ends, vacuum dilemas and now electrical. I am perhaps way over my head so thanks for all the help.

A 300TD is a wagon {the T is for Touring}
The turbo came in during the production cycle of the W123 300D but there was no need to add anything noting it had a turbo. Those of us that know these cars pretty well understand that:
77-81 300D was non-turbo
82-85 300D was turbo
79-80 300TD was non-turbo
81-85 300TD was turbo
300CD's through 1981 were non-turbo, but the turbo was added to the 300CD sometime during 1981, so most aren't but some are in '81.

We don't label wagons with 3rd row seat 300TD3S, or an 82 sedan with rear headrest 300DRH....
Believe the trunk lid!!!

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Jimmy L.
'05 Acura TL 6MT
2001 ML430 My Spare

Gone:
'95 E300 188K "Batmobile" Texas Unfriendly Black
'85 300TD 235K "The Wagon" Texas Friendly White
'80 240D 154K "China" Scar engine installed
'81 300TD 240K "Smash"
'80 240D 230K "The Squash"
'81 240D 293K"Scar" Rear ended harder than Elton John

In some circles, a sedan with a turbo is referred to as a 300D-T. Not to be confused with a 300TD. Or a 300TD-T.

Amateur circles.......

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Jimmy L.
'05 Acura TL 6MT
2001 ML430 My Spare

Gone:
'95 E300 188K "Batmobile" Texas Unfriendly Black
'85 300TD 235K "The Wagon" Texas Friendly White
'80 240D 154K "China" Scar engine installed
'81 300TD 240K "Smash"
'80 240D 230K "The Squash"
'81 240D 293K"Scar" Rear ended harder than Elton John

Noticed that you have said that you have swapped the dash?
I would be looking for the main ground wires.
How long (miles not sitting in the drive way time) has this car gone since the dash change? This issue may be related to that instead of the instrument cluster work?
Buy a cheap meter or three. You will always need them...

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83 300SD Dark Silver Dark brown inside

Fuel and temp gauges acting the same is definitely a bad ground. Mine had a blown trace on the cluster itself. Gotta ask yourself,,, what was the last change I made?

Think I got it. Sprayed and re bolted the ground wires connected to the steering column. Perhaps I bumped these while reinstalling the instrument cluster. Where is the rehostat located at. Both dashes I have had a hole in them just to the left of the column. Perhaps that is my light problem. Installed another dash around six months ago and have had no problems since. Don't think that caused the problem but i suppose it is possible. Sorry if my rehostat question sounds stupid but I could not find any references to it in any of my manuals. Thanks for the help.