Tach only works sometimes!! Help!!

[nphoff]

So the motometer tach and fuel economy gauge on my 1991 325i coupe only work sometimes only after the car has been taken for a drive and then sits in the sun long enough and is then driven again. All other gauges in the cluster work all the time. I replaced the si board batteries. It's not the si board unfortunately. Not the fuses. I wish it was easy.

This makes me think it's some wire or connection that gets contact after heating up enough to expand and get contact. Which leads me to believe it could be connected to the engine bay or near the engine bay. But I don't know whether what to check or where to check exactly.

(My Bentley manual only goes to 1990)

What do you guy think? What and where should I check next?

Thanks for the help!

[Kershaw]

Look at your rear diff, how messed up does the white sensor and it's connection look? Does it look mint? Maybe you need to replace it. If not, then take your cluster out and make sure the connectors are seated properly.

[rturbo 930]

My tach sticks. Have you tried tapping on it when it isn't working?

[TobyB]

Kershaw, you're thinking speedo...

http://www.wedophones.com/BMWManualsLead.htm

The wiring is pretty much all the same from 89-the end.

The wiring diagrams show the wire 'path' through several connectors-
I'd check those first, then suspect the cluster, and finally the ecu tach output itself...

hth,
t

[nphoff]

I checked the blue C1 connector with an electrician and noticed that pin #2 was not there. In my Bentley manual it should be there but it's not. I don't know know if this changed for 1991. (Again, my manual only goes to '90).

There are also a bunch of wires/plugs not connected to anything down by the clutch and brake pedals that I'd really like to figure out what they do. Don't think it's the source of my Tach problem but I'd like to get those cleaned up.

I did read somewhere that the tachometer signal goes to the ecu in the glove compartment then the instrument cluster and that I should check that connection. Does that sound right?

E30 electrical experts please help!

Kershaw, you're thinking speedo...

http://www.wedophones.com/BMWManualsLead.htm

The wiring is pretty much all the same from 89-the end.

The wiring diagrams show the wire 'path' through several connectors-
I'd check those first, then suspect the cluster, and finally the ecu tach output itself...

hth,
t

[nphoff]

I wish mine was just sticky. I tap it and nothing happens. I slam it nothing happens. Haha

My tach sticks. Have you tried tapping on it when it isn't working?

[Zeemz]

Could be that the connection on the actual cluster board is failing and needs to have the solder re-flowed to fix it.

http://www.r3vlimited.com/board/showthread.php?t=147797

[nphoff]

I thought it was this but I had the electrician check all the si board connections in front me for conductivity. We resoldered one part that I scratched putting the car back together one day and now two green service indicator lights go on occasionally and will sometimes stay on even with the ignition off and key out.

But the tach still works after a healthy drive, just not all the time.

I bought the car with the tach working intermittently thinking it would be a simple fix, just replacing the si board batteries. But did that an replaced a weak capacitor and still only works sometimes.

I'm still open to suggestions.

And if anyone knows a good BMW e30 shop in Fairfield county or westchester county (tristate area) that knows e30 electrics let me know.

Could be that the connection on the actual cluster board is failing and needs to have the solder re-flowed to fix it.

http://www.r3vlimited.com/board/showthread.php?t=147797