No Tach

[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]

My 316i has a clock and no obc.

[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.

[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.

[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 ?

[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]

is the radio working ?

[twright]

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

[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 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.