My gas gauge is out of control.

[MR 325]

Ever since I got my 89 running my gas gauge has been out of control, bouncing all over the place and never reading accurately. Luckily the light still works!

Any idea on a fix for thiis? It did not do this before it sat for 9 months but I know this can't be directly related to the motor wiring.

[spoolin318i]

I have the same issue. I think it usually happens when the tank is just 1/4 full.

[WeissE21]

It's the goddamn sending unit!

[atomic]

Having same issue here as well after car sat for 6 months while having work done. Also the SI board lights have quit working all at the same time and I was wondering if that might be the cause or at least part of the problem. I hate to spend $180 on sending units to find out it was the damn SI batteries instead.



EDIT ----- NOT TRYING TO HIJACK YOUR THREAD MATT

[Bimmerista]

I've learned to live with my issue

[RobertK]

Jumping gauges usually indicate that the brass nut on the back of the gauge is loose.

[Ray McCooney]

Jumping gauges usually indicate that the brass nut on the back of the gauge is loose.

+1 to this. You may also want to check the contact points where the actual gauge connects to the board. You may want to use a little sand paper to take care of any form of accumulation on the points/nut and or possibly lay down some new solder. I just had to do the same thing to my latest acquisition, I automatically force myself to overhaul the entire gauge cluster whenever I pick up a new E30, saves me the headache later on. Good luck.

[atomic]

Jumping gauges usually indicate that the brass nut on the back of the gauge is loose.

+1 to this. You may also want to check the contact points where the actual gauge connects to the board. You may want to use a little sand paper to take care of any form of accumulation on the points/nut and or possibly lay down some new solder. I just had to do the same thing to my latest acquisition, I automatically force myself to overhaul the entire gauge cluster whenever I pick up a new E30, saves me the headache later on. Good luck.

In my case I have done the above as I have put another fuel gauge in the cluser trying to remedy this. I made sure the small bent washer was used on the backside of the gauge and the larger flat washer was used under the brass nut. The nut is not loose. And before installing the gauge I did use sandpaper and scuff the contact points to expose fresh metal. So any other suggestions would be helpful. TIA

[atomic]

???

[Ray McCooney]

In my case I have done the above as I have put another fuel gauge in the cluser trying to remedy this. I made sure the small bent washer was used on the backside of the gauge and the larger flat washer was used under the brass nut. The nut is not loose. And before installing the gauge I did use sandpaper and scuff the contact points to expose fresh metal. So any other suggestions would be helpful. TIA

Aside from some fresh solder, I would have to assume that your problem is more restricted to your main board. These are definitely the moments when it works out well to have a couple spare "parts clusters" laying around. Just take a scientific approach to it and systematically replace things and immediately test for results. The main board shouldn't have a dependency on your SI lights/battery, so try replacing the board from another unit. If you are not yard friendly, see if someone near you is either willing to give/sell you cheaply just the main board from a known functioning cluster. Clusters tend to devalue once their speedo/odo or tach.'s stop functioning. Happy tinkering.

[atomic]

Aside from some fresh solder, I would have to assume that your problem is more restricted to your main board. These are definitely the moments when it works out well to have a couple spare "parts clusters" laying around. Just take a scientific approach to it and systematically replace things and immediately test for results. The main board shouldn't have a dependency on your SI lights/battery, so try replacing the board from another unit. If you are not yard friendly, see if someone near you is either willing to give/sell you cheaply just the main board from a known functioning cluster. Clusters tend to devalue once their speedo/odo or tach.'s stop functioning. Happy tinkering.

Thanks for the input! I will add that after swapping out gauges wednesday evening and driving it yesterday that when I made a left hand turn the fuel gauge would go to empty or almost empty. And when making right hand turns it would go to full or almost full. I then put gas in it as I knew it was no where near being full. It held 9 gallons of a 16 gallon tank and still had the floaty needle. So after seeing it respond to different turns I made I am thinking it probably is the sending units now. Sound reasonable ?

I do have the working cluster that came out of the car since the one I am having problems with is a e30 m3 cluster that I put in. I just got the cluster that came from the car out of my storage building and yet to try it out to see results. I also do have a huge source of parts as well since my friend owns a independant BMW repair shop with 10 or so e30's laying around not to mention the stack of clusters in his storage room.

But after the gauge reacting to the car going around turns with just under a half tank of gas in it I am thinking it is the sending units.

[Ray McCooney]

Thanks for the input! I will add that after swapping out gauges wednesday evening and driving it yesterday that when I made a left hand turn the fuel gauge would go to empty or almost empty. And when making right hand turns it would go to full or almost full. I then put gas in it as I knew it was no where near being full. It held 9 gallons of a 16 gallon tank and still had the floaty needle. So after seeing it respond to different turns I made I am thinking it probably is the sending units now. Sound reasonable ?

I do have the working cluster that came out of the car since the one I am having problems with is a e30 m3 cluster that I put in. I just got the cluster that came from the car out of my storage building and yet to try it out to see results. I also do have a huge source of parts as well since my friend owns a independant BMW repair shop with 10 or so e30's laying around not to mention the stack of clusters in his storage room.

But after the gauge reacting to the car going around turns with just under a half tank of gas in it I am thinking it is the sending units.

I would first try swapping in another cluster as you have already stated you will do. From there I would probably check for voltage and ground at the harness connector terminals. Hopefully the cluster swap will remedy the situation. Good luck.

Why the M3 cluster, is your E30 not M20 powered?

[clavinZERO]

pics to help clarify

I snapped some shitty cell phone pics to help directly identify what most people are talking about with the back of the cluster connections.

I know it is pretty self-explanitory, but pics are always nice to have.

The temp / fuel gauges have essentially three pins sticking out the back. There are two smooth pins (one on top and one on bottom), and one threaded bolt right in between those two. BOTH of my gauges had the nuts missing from the threaded bolts, so I put new nuts on with lock washers. So far, the gauges behave better; although, my temp gauge now reads just above notch one -- instead of just below the middle notch.

Pics:

[atomic]

I would first try swapping in another cluster as you have already stated you will do. From there I would probably check for voltage and ground at the harness connector terminals. Hopefully the cluster swap will remedy the situation. Good luck.

Why the M3 cluster, is your E30 not M20 powered?

Thanks for the info. I have yet to have time to get to the bottom of this with all the holiday stuff going on this time of year. But I have plans to get back to it very soon...


Yes it is a m20 powered e30 but I liked the oem look it gives to have oil temp plus the 160mph guage looks cooler, and I have in the plans for a s52 swap in the next year.




:up: