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.do?model=HD13&mospid=47408&btnr=11_1118&hg=11&fg=35


How, please.

[Jay 535i]

Thanks guys.

I do have the Bentley manual. Should I have looked there first? My bad. What should I look for, exactly? A quick look through the index doesn't reveal any obvious clues as to where in the book the solution lies.

[SRR2]

Maybe in the cooling system section if the sender is in the tstat housing as Scott said. The wiring diagram will give you some guidance in identifying what connectors might be in the circuit, but won't tell you where they are. For that you'll have to identify the sender and trace the wiring back to wherever it goes. For sure it will go to the ECU. I'm not sure, but it's possible that the ECU sends the temp signal to the cluster. The wiring diagram will tell you that.

[Paul in NZ]

Jay,if you have a manual take some time and have a read.Honestly if you are interested in your car and how it "works" reading the manual does help.You dont have to read every page,but pick on a section at a time.Start with Fundamentals for the do it your self owner.Also although the index is not organised like you and i would like,if you read the index you will pick up info on where to look.There are no headings for temperature sensor or sensor temperature,but if you look through the index there are general electrical system listings and under Fuel Injection DME there is a Engine coolant temperature sensoe-replacement section,130-14.I do very little work on my car but the manual has helped me sort a few litle niggles myself,or at least helped me narrow the view.And i find it intersting in itself.The ect sensor is right next the the temperature gauge sensor(or is it the other way round?)

[Jay 535i]

Jay,if you have a manual take some time and have a read.Honestly if you are interested in your car and how it "works" reading the manual does help.You dont have to read every page,but pick on a section at a time.Start with Fundamentals for the do it your self owner.Also although the index is not organised like you and i would like,if you read the index you will pick up info on where to look.There are no headings for temperature sensor or sensor temperature,but if you look through the index there are general electrical system listings and under Fuel Injection DME there is a Engine coolant temperature sensoe-replacement section,130-14.I do very little work on my car but the manual has helped me sort a few litle niggles myself,or at least helped me narrow the view.And i find it intersting in itself.The ect sensor is right next the the temperature gauge sensor(or is it the other way round?)

Thanks. I know you're right, but I tend to use this forum as a first go-to rather than a last resort. The answers I get here are just so much better than those in the book. But you're right, I should check the book first, and set a goal of reading it for background.

[DanDombrowski]

I was wondering if you ever resolved the issue, because I think my car is acting up in the same way. It dropped to cold a few weeks ago, so I thought the Tstat was stuck open. One day, it just shot right up to normal, so I kind of put off replacing the T-stat (its on my workbench). The odd part was how quickly it came up to normal, just like you said yours did.

The other day, it did it again, only it dropped down really quickly. I checked the heat, and I have really, really hot air coming out of the vents, so I think its a gage problem.

Now here comes the really odd part: The gage doesn't "not work". It actually comes just ever so slightly above the blue region when hot. It also takes about the same amount of time to get from the bottom of the blue (just turning on the car) to the top of the blue (normal position when not working) as it usually does to warm the car up to halfway. This leads me to believe it really is a gage/sensor problem, not a tstat problem.

Because the gage acutally does move, I don't think its a capacitor problem. If the capacitors were leaking, it wouldn't work at all. The way it works sometimes and not others makes me think that its a loose connection (or the coolant temp sensor is reading intermittantly).

I think the first thing I'm going to do is clean the contact for the coolant temp sensor, or possibly pull the sensor and see if it needs to be cleaned or anything. If that doesn't work, I'll replace the sensor.

What I would really like to do is what I do with OBDII cars, and that's use my diagnostic tool to read the coolant temp straight from the ECU to rule out the gage being bad, but I can't do that with this car. Mabye a function in the OBC will let us do that? I looked up the functions, but I didn't see a coolant temp option.

Ok, thanks for reading this. Hopefully we can get this worked out!

[bimmerd00d]

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.

Did 90's have capacitors? i thought model year 90 was the upgrade, or was that production year 90?

[Bill R.]

own which is a production date 9/88



Did 90's have capacitors? i thought model year 90 was the upgrade, or was that production year 90?

[Jay 535i]

I was wondering if you ever resolved the issue

It resolved itself. I haven't seen the issue resurface since I started this thread.

My coolant level was low, if that could possibly have had anything to do with it.

[ryan roopnarine]

everything on my cluster works fine so long as its above 25. it got below that, and my tachometer started brake dancing, going backward. speedometer, tach, fuel didn't work, but temps did. normal temps=normal function. yours might be going out slowly. you can read the temp value using a VOM on the temp sensor, if you want to rule things out.


I was wondering if you ever resolved the issue, because I think my car is acting up in the same way. It dropped to cold a few weeks ago, so I thought the Tstat was stuck open. One day, it just shot right up to normal, so I kind of put off replacing the T-stat (its on my workbench). The odd part was how quickly it came up to normal, just like you said yours did.

The other day, it did it again, only it dropped down really quickly. I checked the heat, and I have really, really hot air coming out of the vents, so I think its a gage problem.

Now here comes the really odd part: The gage doesn't "not work". It actually comes just ever so slightly above the blue region when hot. It also takes about the same amount of time to get from the bottom of the blue (just turning on the car) to the top of the blue (normal position when not working) as it usually does to warm the car up to halfway. This leads me to believe it really is a gage/sensor problem, not a tstat problem.

Because the gage acutally does move, I don't think its a capacitor problem. If the capacitors were leaking, it wouldn't work at all. The way it works sometimes and not others makes me think that its a loose connection (or the coolant temp sensor is readin

g intermittantly).

I think the first thing I'm going to do is clean the contact for the coolant temp sensor, or possibly pull the sensor and see if it needs to be cleaned or anything. If that doesn't work, I'll replace the sensor.

What I would really like to do is what I do with OBDII cars, and that's use my diagnostic tool to read the coolant temp straight from the ECU to rule out the gage being bad, but I can't do that with this car. Mabye a function in the OBC will let us do that? I looked up the functions, but I didn't see a coolant temp option.

Ok, thanks for reading this. Hopefully we can get this worked out!

[KenB]

this happened to my car also, it was a bad sensor.

[Jay 535i]

this happened to my car also, it was a bad sensor.

Did you discipline it?

Bad sensor! Bad, bad sensor!!

[KenB]

Bad, faulty, non-working, whatever you want to call it. yes, it was severely punished and is now removed from its' position and will no longer have any chance to be BAD again. :)