Tach issues

[Buckeye]

Good morning, I have had this issue since I purchased my 1993 500e 11 years ago. My tach does not work until I get the car up to 15-20 mph. After that it works fine. Both upper and lower wire harnesses have been replaced. This is not a huge problem but I would like to get it fixed. Thanks

 

[gsxr]

There's a chance the tachometer itself is faulty / flaky. The 400E tach is identical and fairly commonly available, you could buy a used one (might need to buy a complete 400E/E420 cluster) and swap it out.

Alternately, you could try to find an electronics shop (perhaps a VDO repair shop) willing to try and repair your existing tach, but unless there's obvious failures like deceased capacitors, I don't know if this is feasible.

 

[nocfn]

or turn on the car first thing in the morning and if the tach is not working, give the dash a sharp wrap with the heel of your right hand and that should wake it up.... until the next time. I get this on the 126 and 124 occasionally between stretches of non-use.

 

[R129 UK]

HHT-Win has a test feature which moves all the gauges from min to max which tests the cluster operation with the engine off.

I assume this would work on a 93 500E too and might give some clues to what is wrong if you have access to Xentry / DAS & HHT-Win etc.

 

[Buckeye]

I tapped the dash this morning and it woke up my tach. It preformed as normal. Thanks for the advice

 

[R129 UK]

I tapped the dash this morning and it woke up my tach. It preformed as normal. Thanks for the advice

Nothing beats a bit of "gentle persuasion"

 

[gsxr]

HHT-Win has a test feature which moves all the gauges from min to max which tests the cluster operation with the engine off.

I assume this would work on a 93 500E too and might give some clues to what is wrong if you have access to Xentry / DAS & HHT-Win etc.

Later R129 have digitally-controlled gauges which can be manipulated via HHT-Win.

The 500E (and all 124 chassis) have old-school analog gauges with no computer control, nothing for HHT-Win to communicate with.

 

[gsxr]

I tapped the dash this morning and it woke up my tach. It preformed as normal. Thanks for the advice

This confirms the tach itself is probably bad. If you continue to have the problem and tire of whacking the cluster, replace the tach/clock gauge assembly.

 

[nocfn]

I agree with the GSXR. Other than the occasional need to wake her it up, the refection of idle speed appears accurate.