Hi - I've got a 1990 GMC 5.7L 4x2 pickup. When I turn it on, the temp
gauge goes all the way to the left and stays there (and when I turn it
off, it goes all the way to the right). Also, when I put my turn
signals on, the voltmeter moves left to right to left to right with
the ticking of the lights. I'm guessing this is a crazy electrical
thing, but where exactly under the hood should I be looking?
Doug Adams - 29 Mar 2007 02:03 GMT
Sounds like a ground problem I would check the ground wire connecting the
engine to the body. Actually all grounds in general.
> Hi - I've got a 1990 GMC 5.7L 4x2 pickup. When I turn it on, the temp
> gauge goes all the way to the left and stays there (and when I turn it
> off, it goes all the way to the right). Also, when I put my turn
> signals on, the voltmeter moves left to right to left to right with
> the ticking of the lights. I'm guessing this is a crazy electrical
> thing, but where exactly under the hood should I be looking?
Mike Marlow - 29 Mar 2007 11:23 GMT
> Sounds like a ground problem I would check the ground wire connecting the
> engine to the body. Actually all grounds in general.
Likely, it is a ground problem - in a round about way. The sender unit
provides a variable resistance ground path, which is what causes the needle
deflection. Sounds like his sender is bad, therefore the ground path is
bad. In this case though the body ground is not likely to be the culprit.

Signature
-Mike-
mmarlowREMOVE@alltel.net
Mike Marlow - 29 Mar 2007 02:07 GMT
> Hi - I've got a 1990 GMC 5.7L 4x2 pickup. When I turn it on, the temp
> gauge goes all the way to the left and stays there (and when I turn it
> off, it goes all the way to the right). Also, when I put my turn
> signals on, the voltmeter moves left to right to left to right with
> the ticking of the lights. I'm guessing this is a crazy electrical
> thing, but where exactly under the hood should I be looking?
For the temp gauge problem you need a new sending unit. There are a couple
(or a few) different temp senders for each of the engines and they all have
a different resistance. You'll need to provide your VIN in order to get the
right sending unit with the right resistance.
As for your directions and your meter - if all of your lights are working
properly then don't worry about it.

Signature
-Mike-
mmarlowREMOVE@alltel.net