Tacho prblem

[The Big Man]

Hi Guys
I have a problem witht the tacho on my 1996 E300D (W124).
Recently it has started to fall to zero when idling and engine becomes rough. At higher revs it seems to read normally but this too is becoming erratic. A few months ago I did blow the fuse on the OVP but it has been fine untill recent weeks. I have swapped the relay from another 124 and it made no difference. The ABS light is not lit

Any ideas much appreciated

The Big Man

 

[Bolide]

1 - AFAIK the tacho is driven off the alternator. 2 - why did the OVP fuse blow?

I think the two things are related and I'd be looking at the alternator for answers

Nick Froome
www.w124.co.uk

 

[The Big Man]

Hi Nick

The OVP fuse blew because I had a glow plug short to earth and heater relay caused cable to melt one morning so I had to renew some of the cables along with glow plugs

 

[television]

Dont think so Nick the tach on a diesel was an extra or retro fit in place of the clock

It looks to me as though the TDC sensor is fitted to the front of the engine and wired to the Diag socket and taken on from there

If I send you the retro fit its all there

 

[The Big Man]

If the tacho does not get a signal then will the OVP fail to o/
perate hence the rough idle

 

[television]

The OVP relay can give a rough idle on a late 124

 

[The Big Man]

I did have those symptons when the fuse was blown on top of the OVP but it is fine now and I have tried another in its place whichmakes no difference. Does the relay take a signal from the tacho or vice versa?

 

[television]

I did have those symptons when the fuse was blown on top of the OVP but it is fine now and I have tried another in its place whichmakes no difference. Does the relay take a signal from the tacho or vice versa?

This is nothing to do with the alternator or OVP relay, I can send you a paper with it all in

 

[The Big Man]

Hi Malcolm

That would be great. Can you pm it to me,

 

[television]

I need your Email address

 

[The Big Man]

Do I just post it here?

 

[television]

Put it up hare then in a few minI will tell you to go back to the post and in "edit" you can take it away

 

[television]

OK I have sent it,, go back to your post and delete the address or the whole message in edit

 

[The Big Man]

Ok
Thanks for that. I shall take a look and see if I can get to the bottom of this

 

[television]

Ok
Thanks for that. I shall take a look and see if I can get to the bottom of this

The TDC sensor is fitted at the front of the engine by the front pulleys and belts, the rest is in the diagram, and good luck