84 BMW 325e RPM Gauge not working anymore

[turtlerevor]

Recently my RPM gauge stopped working, I replaced the 21 fuse and it started again for a while but recently has gone out again. I replaced the 21, 12, and 10 fuses and still nothing this time. I have recently replaced the SI board with a batteryless one (don't know if that was a good choice yet) but so far, my oil indicator lights are working when starting the car. Every gauge but the RPM gauge is working normally (better than before I replaced the SI board). I have been looking and so far, I have seen people recommend replacing the SI board with a new one or new batteries.

The person I got the car from gave it to a -lets just call him not so proficient- mechanic who decided 1 bigger battery was better than 2 smaller ones. Turns out that wasn't a good idea as the oil indicator lights never worked, tach and temp gauge were wonky. (another one of that mechanics thought was to hold the radiator shroud with a bent spoon. Innovative ill give him that.

I just want a couple more ideas to do and if I need to swap the board again I will just want to try to avoid doing that if I can. But it seems ive hit a wall and could use the help!

Thanks,
Trevor

[Tom Galloway]

I got the same thing except sometimes the mpg gauge goes out too and the temp gauge never gets hot - just out of the blue / the gauge pegs when I ground out the lead ---

So - what to do - My plan is to make sure all the wires going to the unit are tight - the p.o. removed the cluster several times to fix the speedo but the problem was a broken wire on the sensor. In the process looks like he may have stressed the connections.

Generally I think BMW's never break ( yeah) but do get corroded, lose , dirty, abused, cussed out, etc..

Blast it with cleaner and good luck.

tg

[turtlerevor]

Hmm my mpg gauge works, and the temp gauge goes to the middle like it should, ill check the wires behind the cluster and reclean it out, ill also check some ground points within the car just in case.

Thanks!

[turtlerevor]

Update: when I got in it this morning (car was sitting for about a week in the freezing weather) and drove it for a couple minutes the rpm gauge was going in and out. Then when I parked the car the gauge was working properly like nothing happened. Still no clue what is happening but glad its working as of now but would still like to fix that intermittent problem if at all possible.

[reelizmpro]

The tach on the 84-85 cars isn't run by the SI board like the later cars assuming you have the correct cluster so battery replacement won't affect it. In fact, you can remove the entire SI board and it will still work. In your case, I would suspect cracked solder joints on the tach board or main PCB. Post of a picture of your instrument cluster to confirm what you have.

[turtlerevor]

The tach on the 84-85 cars isn't run by the SI board like the later cars assuming you have the correct cluster so battery replacement won't affect it. In fact, you can remove the entire SI board and it will still work. In your case, I would suspect cracked solder joints on the tach board or main PCB. Post of a picture of your instrument cluster to confirm what you have.

I will have to try that out, when I get back home ill take a photo and upload it here as well. Thanks for the tip!

[turtlerevor]

The tach on the 84-85 cars isn't run by the SI board like the later cars assuming you have the correct cluster so battery replacement won't affect it. In fact, you can remove the entire SI board and it will still work. In your case, I would suspect cracked solder joints on the tach board or main PCB. Post of a picture of your instrument cluster to confirm what you have.

I checked the solder joints everything was getting the proper connections and nothing was broken. resolder a couple just in case but when driving still same issue.

*while playing around with the board plugged in but not fully installed noticed my battery light was out. I moved the cluster around and the light came back on. long story short found out the wires to the connector are not perfect and are not connecting properly all the time. I dont know if i need to repin or just replace the wiring- seems to be the last 6 inches of wire is where the break is im thinking the pins since im sure they have not been redone or replaced ever they are cracked, or just need to be replaced. When starting the wiring seems to affect the temp gauge and battery light as well.

I ended up wiring in a resistor on the cluster board to give the alternator power to the signal when starting to skip over that light until i fix the wiring so it charges the battery still. But I am still having the issue with the rpm gauge coming in an out and temp gauge with the battery light not coming on always as well. starting to think need to redo all of the wiring soon.

[turtlerevor]

After fixing the battery charging issue (or temporarily fixing) the car has been idling very bad to the point now where i need to depress the pedal while cold start to stop it from dying. Possible ICV or Idle control module from what I have been hearing, will need to check the icv for buzzing and the resistance and voltage still. I have a another module that I will test with for that, and I will try disconnecting the brown temperature switch and see if that has any affect as well. The last thing that would be in my mind is the AFM meter as it has been opened by the previous owner. Or another wiring issue. We will see.

[turtlerevor]

After fixing the battery charging issue (or temporarily fixing) the car has been idling very bad to the point now where i need to depress the pedal while cold start to stop it from dying. Possible ICV or Idle control module from what I have been hearing, will need to check the icv for buzzing and the resistance and voltage still. I have a another module that I will test with for that, and I will try disconnecting the brown temperature switch and see if that has any affect as well. The last thing that would be in my mind is the AFM meter as it has been opened by the previous owner. Or another wiring issue. We will see.

adjusted the idle set screw and the icv valve screw and it idles great for a couple seconds then starts to run horribly rich and continues till it dies. I tested the temperature sensor and that was not reading
anything. I have a new one going to replace that and see if that fixes my horrible idle. - also had to do wiring repair for the icv but that is completed

[jeffnhiscars]

There are 2 sensors on your bell housing on an eta. IIRC 1 is your crank sensor and the other is for your tach they look identical so don't mix them up

[turtlerevor]

There are 2 sensors on your bell housing on an eta. IIRC 1 is your crank sensor and the other is for your tach they look identical so don't mix them up

I haven't taken then off and would that come to an intermittent issue?

[jeffnhiscars]

I haven't taken then off and would that come to an intermittent issue?

Intermittent issues are typically random so harder to pin point. A bad wire is often the cause and can be anywhere