Electrical problem. Can anyone help?

[texastruckjunky]

I have a 1981 1/2 ton. I have recently replaced the sending unit for the gas tank, and now when I turn my lights on the gas gauge goes to empty. Can anyone tell me why or how I might be able to fix this. I dont do a lot of night time driving, but I dont want it to turn into a bigger problem later. Thanks for your help in advance.
Rey

[rs72z]

Make sure you grounded the sending unit. Check all the grounds on th front end also.

[hatzie]

If it works till you turn on the headlights there's probably a ground problem behind the instrument cluster.
There's a big splice where the Black cluster plug grounds are all connected to a single ground wire from the ground bar under the dash. The Pink/Black cluster power wires have the same type of splice.
The panel lamp ground is probably wonky.

[motornut]

yup sounds like a ground issue

[texastruckjunky]

Originally Posted by rs72z

Make sure you grounded the sending unit. Check all the grounds on th front end also.

It was all working till this morning, I replaced the fuel sending unit about a month ago. But thanks for the help anyways.

hatzie: Thanks for your reply I'll have to check that in the morning. I remember when I replaced the sending unit the guage still did not mark, when I pulled the cluster out the plug in the back had corrosion on it like the truck had gotten wet or was under water at some time. I think it was under water cause there was also leaves, twigs and dirt all up under the dash. So I replaced the cluster with another one i had . So i'll get back in there toomorrow and check it again. Thanks
Rey