Eliminare dancing temp gauge when turn sigs are on???

[bavariaboy]

The needle on my temperature gauge bounces up and down with the turn signals. It also moves up when I turn on the running and/or headlights. And it may go up when I apply the brakes, not sure about that.

 

Is there any way to eliminate this annoying and the case of the lights inaccurate temp gauge reading?

 

thanks, 

 

Steve

[beammmer]

Check all grounds. Maybe add one to the instrument cluster. And that will do it.

 

Don

['76mintgrün'02]

What Don said.  One common solution is to add an extra ground wire to these little nuts.  It usually solves the jumpy gauge problem.  Thanks for that tip @zinz : )  I just made a little copper strap, instead of a wire.

 

 

[ingramlee]

Also check the female spade connector that plugs onto the sensor itself. I chased this problem for months, doing and re-doing ground connections.  I finally took a pair of pliers and slightly closed the end of plug to make it tighter and my temp gauge hasn't bounced since... 4 months now.

[popovm]

1 hour ago, '76mintgrün'02 said:

What Don said.  One common solution is to add an extra ground wire to these little nuts.  It usually solves the jumpy gauge problem.  Thanks for that tip @zinz : )  I just made a little copper strap, instead of a wire.

 

 

 

That little strap is so satisfying. 

[72MetallicMalaga]

Question for the forum, out of curiosity, has this always been the case with the needles when these cars were sold new?

 

I haven't noticed, but mine do this as well. Very slight movement. Noticed it after I swapped the alternator for a reman Bosch 35amp, but I don't know if it did it before the swap...

[Son of Marty]

Not when new, the bouncing came later as the grounds started to age aided by BMW habit of putting rubber bits between everything.

[JohnS]

2 hours ago, '76mintgrün'02 said:

What Don said.  One common solution is to add an extra ground wire to these little nuts.  It usually solves the jumpy gauge problem.  Thanks for that tip @zinz : )  I just made a little copper strap, instead of a wire.

Did the "B" in the "BMW" stamping on that strap get covered up by the nut?  That is an awesome solution.  Love your work!  😀

John

['76mintgrün'02]

7 minutes ago, JohnS said:

Did the "B" in the "BMW" stamping on that strap get covered up by the nut? 

 

Nope.  I managed to squeeze all three stamps in there. 

 

Here's another BMW stamp I have and a piece of 1/8" copper I used it on. 

 

 

I had to hit it a bunch of times to get it this deep.

 

[John76]

I try to check all the grounds (42 as of last count) and found the fuel gauge jumps only when the right turn signal is used.

Solution was to add an extra ground wire to the fuel sender (green wire in photo). Fuel sender and right-side lights (except headlights) share a common ground.  Solved the problem ... never did find the original cause.

 

 

 

[popovm]

I recently did a forum search on this and some people were calling out the battery ground strap as another possible culprit. I think that applies to me since the gauge jumps when I turn off or on most anything electrical. 

[Mike Self]

Another thing to check when it's the temp gauge...the sender unit ground through its threads where it's screwed into the water manifold on the cylinder head.  Brass sender, aluminum manifold = dissimilar metal corrosion, which means a poor ground.  

 

Lower the coolant level a bit, unscrew the sender, clean the sender and manifold threads with a stainless steel "toothbrush", reinstall without using any sealer or teflon tape.  

 

Oh, and make sure the ground wire you make for the back of the instrument cluster is long enough to allow you to remove/replace the cluster...

 

mike

[dferg]

One of the best things (and Cheapest) I ever did to my '74 was change the original 45 year old battery/engine ground cable with a new OEM. Came from Blunt, but is available from others. 

Charging and starting dramatically improved. Often overlooked.

[7502]

After trying the normal solutions for the bouncing temp gauge including the extra ground on the back of the gauge cluster - mine would even bounce in sync to songs w/ a heavy baseline from the subwoofer.  I eventually added a ground strap from the battery to the forward sheet metal on the nose.  Good luck.

 

 

[jimk]

For what it's worth - when the small ground strap between the fender and the battery has poor connections or is in bad shape, the devices on the body that need ground to the battery take the current, the voltage will find another route through the instruments connected to the engine.  It then uses the main engine ground strap to the battery.  In the case of the turn signals, the temp gauge goes high. (C'mon @calw help a mechanical out).

Fix it and the signals will be brighter too.

Edited September 16, 2022 by jimk