Headlight Switch and Temp Gauge

[Chief Brody]

74 K5 Blazer

When I pull the lever on my headlight switch, the temp gauge goes over to the 3 o'clock position and sticks there.

I have a new headlight switch. I have cleaned and reinstalled all ground points installing new straps.

I am baffled....what else could it be?

 

[British Slave]

Maybe a dash light shorted on the circuit board?????????

 

[Chief Brody]

Maybe a dash light shorted on the circuit board?????????

All lights appear to be working on circuit board...I put all new bulbs in it.

 

[Chief Brody]

Anybody think a new circuit board is the answer? or must it be a ground problem?

What the heck do the headlights have to do with the temp gauge?

 

[British Slave]

They are not supposed to have anything to do with each other, but they are both mounted to the printed circuit. It sounds like a ground issue. The dash lights MAY be grounding thru the gauge. I would start by turning on the lights, getting the gauge to do what you say and then unplug each dash light one at a time to see if it changes the problem.

 

[Chief Brody]

They are not supposed to have anything to do with each other, but they are both mounted to the printed circuit. It sounds like a ground issue. The dash lights MAY be grounding thru the gauge. I would start by turning on the lights, getting the gauge to do what you say and then unplug each dash light one at a time to see if it changes the problem.

I will try that...

 

[Fordum]

You have the most......Interesting problems....

Check out these schematics.
I see three different grounds in the instrument panel. If they are good, you need to make sure that the piece of metal they are grounded to is grounded.

Don't be too proud to run a long wire from the negative terminal of the battery and touch it to different parts that are supposed to be grounded to see if the problem goes away.

Thats a favorite trick of mine when I suspect a bad ground.

 

[Chief Brody]

Thanks for the schematics...I will have to try the negative wire trick...I have run out of options. Removing bulbs did nothing. I also noticed that my fuel gauge is kind of stuck...stiff when I try to move the needle. Whatever is affecting the temp gauge is affecting the fuel gauge as well.

Something has definately changed...it was fine up until I changed the o-ring on the dipstick tube. That's the day it started acting up. I didn't change anything else...can't imagine what could have done it.

 

[Chief Brody]

I finally got in there with the instrument cluster bucket out again and I hit the ground point with the wire brush on the drill and plugged the harness in and tested...still did the same thing.

I ran a wire from the battery negative to the ground point in the dash...plugged in the harness and it appeared to work. The temp gauge just barely flicked this time when I turned on the headlights....so I reassembled the instruments and dash.

Once I had it together I pulled the light switch and the temp gauge went up to half...I nearly pulled my hair out...
Then I turned the key and started the engine and quickly it snapped to "C"...where it should be....it appears that my gas gauge is now working also.

Does anybody have any ideas as to why it works fine with the engine running but not when the key turned to the off position? The temp gauge climbs about 25% every time I pull the headlight switch but snaps back when I start engine....

 

[imiceman44]

I finally got in there with the instrument cluster bucket out again and I hit the ground point with the wire brush on the drill and plugged the harness in and tested...still did the same thing.

I ran a wire from the battery negative to the ground point in the dash...plugged in the harness and it appeared to work. The temp gauge just barely flicked this time when I turned on the headlights....so I reassembled the instruments and dash.

Once I had it together I pulled the light switch and the temp gauge went up to half...I nearly pulled my hair out...
Then I turned the key and started the engine and quickly it snapped to "C"...where it should be....it appears that my gas gauge is now working also.

Does anybody have any ideas as to why it works fine with the engine running but not when the key turned to the off position? The temp gauge climbs about 25% every time I pull the headlight switch but snaps back when I start engine....

I remember my 74 the guages didn't properly work except with a running engine, coincidence or normal, I don't know.