Red Tacho light on constantly

[Mr M]

Anyone else had this. I read in the manual it's supposed to go on when peak revs have been reached to indicate a gear change.

[morebeanz]

I've not had it, but the Cerb electrics are fairly Heath Robinson! Worth checking for a short behind the dash, or a fault in the sensor.

[shpub]

Err.... there is no sensor. This is driven directly from the ECU. To turn it on the signal wire is grounded. So it is either a fault in the wiring or something wrong in the ECU.
Equally it could be that the ECU software has become corrupt and the shift light limit is now set to below the idle.

I would suspect a wiring fault of some kind.

[julian64]

Wot e said

The tacho signal from ECU to gauge has got itself earthed.

Not a good idea to leave it that way because the little chip that drives the tacho signal also drives a few more important things in your car, and is possibly under a bit of strain at the mo.

[Mr M]

Thanks all. Car is in fact driving very well apart from that little niggle and I believe it has been doing it since I purchased it from Offords last May. Obviously an added cost option to have it fixed at the time

PS Julian - what other important things would they be do you know ?

Edited by Mr M on Friday 4th January 15:07

[julian64]

Mr M said:

Thanks all. Car is in fact driving very well apart from that little niggle and I believe it has been doing it since I purchased it from Offords last May. Obviously an added cost option to have it fixed at the time

PS Julian - what other important things would they be do you know ?

Edited by Mr M on Friday 4th January 15:07

I take it all back. The tacho signal is controlled by a little chip on the ECU called hip008. A small line driver chip. It controls the fault pin, tacho pin, pin14,pin15 and pin34 on the ECU connector which I believe in the Cerb powers exactly nothing

[Mr M]

Thanks Julian - good stuff and into my filing cabinet it goes and reminds me I must try and download some of those technical pdfs at some point.

[Mr M]

Thanks Julian - good stuff and into my filing cabinet it goes and reminds me I must try and download some of those technical pdfs at some point.