No Tach

[twright]

I recently purchase a 1993 BMW 316i Touring (Yes, another one.)

The car is in pretty good shape, but I am having trouble getting the tach to work. I have tried all of the usual things (i.e. swapped several know good clusters, verified good power coming all the way from fuse 41, swapped several known good SI boards, verified a solid square wave signal from the black wire on the blue connector on the back of the cluster, etc.) but I still can't get it to work.

Anybody got any more things to look at?

P.S. The fuel economy gauge doesn't work either.

[82eye]

swapped tach will only work if it's off another 4 cyl car. i'm not certain an m42 tach will work but believe it should.

check the SI batteries on the original board. if the tach or speedo doesn't work the econo gauge won't either.

[twright]

I changed the SI batteries in the original board: no change. Still no Tach.

[82eye]

is the radio working ?

[AWDBOB]

swapped tach will only work if it's off another 4 cyl car. .

This is incorrect- 7k tachs are the same between 4 and 6cyl cars. Only coding plug is different between 4 and 6 cyl 7k tach

Tom you almost certainly have a fuse 21 issue- especially since you had to get power to the radio from another source

[82eye]

This is incorrect- 7k tachs are the same between 4 and 6cyl cars. Only coding plug is different between 4 and 6 cyl 7k tach

thought the tach determined the coding plug. i've also read fuse 12 as tach and radio and 21 for obc.

edit : don't think 316i even has an obc. aren't they all clocks ?

[82eye]

Tom you almost certainly have a fuse 21 issue- especially since you had to get power to the radio from another source

didn't add i'm guessing someone accidentally grounded the original radio circuit as well.

[twright]

The radio did not have a battery connection and wouldn't work. I have connected the fuse 21 circuit to battery and the radio works now.

[twright]

My 316i has a clock and no obc.

[82eye]

The radio did not have a battery connection and wouldn't work. I have connected the fuse 21 circuit to battery and the radio works now.

the tach is on the same circuit.

[twright]

I have a Tach! It turns out the Fuse 21 wiring was NFG.

AWDBOB for the win!

[82eye]

I have a Tach! It turns out the Fuse 21 wiring was NFG.

AWDBOB for the win!

nice work. thanks for posting the fix. wish more folk would do that.

[Gtfour]

I also have a tach question. I have a 318is. The tach is working but the rpm doesn’t match the actual engine rpm. It’s going to like half of the real rpm. Could it be mismatch parts from a 325 or early model? I bought it from a guy who had couples of E30 and bunch of spare parts and I have parts frim couple different cars on it…

[82eye]

I also have a tach question. I have a 318is. The tach is working but the rpm doesn’t match the actual engine rpm. It’s going to like half of the real rpm. Could it be mismatch parts from a 325 or early model? I bought it from a guy who had couples of E30 and bunch of spare parts and I have parts frim couple different cars on it…

sounds like what you suspect.

[Gtfour]

sounds like what you suspect.

Yes but if I have the 318is original cluster, what is the other part that isn’t compatible with it?