Malfunctioning temp guage

[Jay 535i]

The coolant temp guage on my dashboard seems to be on the fritz these last couple of days.

It will sometimes dip into the blue zone, or hover somewhere in the left-half of the dial when I know the engine is up to temp (HVAC air is very warm).

The needle will periodically hit its usual mark (i.e. vertical), but not stay there.

Since the air coming out of the vents is always very warm, I suspect a problem with the sensor rather than an overcooling problem with the engine.

Any advice?

[SRR2]

Funky capacitors in the instrument cluster can do this, and your car is plenty old enough for the caps to be bad. Is anything else on the cluster acting up now and then? If you've already eliminated this, it might be a bad connection, however bad connections would more likely cause high readings. It wouldn't hurt to re-seat the connectors on the sender.

[Jay 535i]

Funky capacitors in the instrument cluster can do this, and your car is plenty old enough for the caps to be bad. Is anything else on the cluster acting up now and then? If you've already eliminated this, it might be a bad connection, however bad connections would more likely cause high readings. It wouldn't hurt to re-seat the connectors on the sender.

Everything else works fine.

Where is the sender? I also suspect a loose connection somewhere, since the problem is intermittent. When the needle does move, it moves very briskly, leading me to think there's an electrical connection somewhere that's loose and is getting disconnected and reconnected periodically.

Funny how the needle never moves right of center. The malfunction seems to always send the needle to the left -- never the right. Does that mean anything?

Thanks.

[DaCan23]

Usually on an issue like this, many suggest to check all the ground connections on the car. About 1/2 the time its a bad ground.

[Jay 535i]

Usually on an issue like this, many suggest to check all the ground connections on the car. About 1/2 the time its a bad ground.

How do I do that?

Please excuse my ignorance. I even amaze myself at how I manage to know so much about cars and so little about working on them. I guess that what comes from getting all your knowledge from reading rather than from getting greasy.

[DaCan23]

I cant say I am a pro at inspecting grounds, nor do I know the 4-6 grounding spots on the E34 outside of the hood, alternator, & battery. But at the connections look for corrosion, clean them w/ wire brush, and/or buy & attach new grounding cable if needed.

How do I do that?

Please excuse my ignorance. I even amaze myself at how I manage to know so much about cars and so little about working on them. I guess that what comes from getting all your knowledge from reading rather than from getting greasy.

[Paul in NZ]

when my temp guage was doing this i cured it by simply unplugging and replugging the connectors a few times!

[Jay 535i]

when my temp guage was doing this i cured it by simply unplugging and replugging the connectors a few times!

How, please.

[SRR2]

Jay, you need to buy yourself the Bentley book for your car. I'd be happy to help you out, but I don't have mine any more. Someone here should be able to tell you where the sending unit is. I think it's on the lower left side of the engine, but honestly I don't remember that clearly.

As far as grounding goes, you could spend a half lifetime chasing down all possible grounding points, but it's true that one critical bad one can screw things up pretty badly. I'd go after the sender first. Even though it's a PITA, you might try reseating all the connectors on the back of the cluster. That would be a good time to put in new lamps for the odo, cc, and trans annunciators.

[Scott H]

on the t-stat housing, right behind the fan. Sounds like intermittant or poor connection.

http://www.realoem.com/bmw/showparts...18&hg=11&fg=35

How, please.