electrical and ignition Tachometer Not Working

[briantmac]

Hello,

My tachometer (a.k.a. Rev counter) is not working.  My mechanic pulled my tach and installed his tach (from 02) and his tach worked in my car.  So, that tells me that my tach is broken.  Has anybody successfully repaired their tachometer?  Or, can anyone recommend a shop to send my tach to?

 

Much thanks!

 

[M3M3]

north hollywood speedometer

 

they fix all the VDO stuff and it comes back looking new.

[TimMN]

If you want to try to fix it yourself and are not afraid of a soldering iron it it possible. I've found that tachs that sit for a long time without being used have bad electrolytic capacitors. Pull the tach apart and replace them. I've had several come back to life.

 

TimMN

[tlapham]

Sorry to be such a bum, but when you say "my mechanic replaced mine with his and it worked, that tells me mine is bad" i just don't trust it. It is soo easy for those wires to come loose from a bump or vibration, and when you pull the gauge cluster, they usually pop off anyway, so you can't tell if it was on or off before...

 

Test it yourself to be sure, before you start tearing into it.

[briantmac]

I was working on the tach last night.  I had an old aftermarket tach and I wondered if it still worked.  So, I hooked it up to the 02, direct to components in the engine compartment.  And it worked.  While I was working around the coil, i noticed a black wire that was broken.  It went from coil (neg side) to distributor condensor and then I'm not sure where it went.  So, I soldered it back together .  Checked the cars tach, still no worky.   Then I pulled my cluster and tried wiring the 02 tach direct in the engine compartment and it worked.  SURPRISE!!  I thought I might still have a wiring problem, so I RECONNECTED  the cluster and used my voltmeter to test the grn,brn,blk wires for the tach.  The grn & brn wires showed me 12VDC.  That's good.  Then I went to brn and blk wires and they showed a 6.98 - ? VDC.  It was varying, kind of like I would expect a coil to do.  But it did the same thing in the engine compartment and I figured that meant my wire was not broken.  That is good too.  Then  I reconnected to the tach and it has been working.  Not sure what I did but it is working.  Thanks for your help...

[briantmac]

I just want to correct something that I said; I did not test the brn (ground) and blk (neg side of coil). Rather, it was the grn(+) and blk wire. This test gave me a 6.98 +- varying voltage. I am not sure that this is a valid test but I was just looking for the same voltage inside the car as I got in the engine compartment. I used that result to tell me that I didn't have a short in the wire.

[M3M3]

 

I was working on the tach last night.  I had an old aftermarket tach and I wondered if it still worked.  So, I hooked it up to the 02, direct to components in the engine compartment.  And it worked.  While I was working around the coil, i noticed a black wire that was broken.  It went from coil (neg side) to distributor condensor and then I'm not sure where it went.  So, I soldered it back together .  Checked the cars tach, still no worky.   Then I pulled my cluster and tried wiring the 02 tach direct in the engine compartment and it worked.  SURPRISE!!  I thought I might still have a wiring problem, so I RECONNECTED  the cluster and used my voltmeter to test the grn,brn,blk wires for the tach.  The grn & brn wires showed me 12VDC.  That's good.  Then I went to brn and blk wires and they showed a 6.98 - ? VDC.  It was varying, kind of like I would expect a coil to do.  But it did the same thing in the engine compartment and I figured that meant my wire was not broken.  That is good too.  Then  I reconnected to the tach and it has been working.  Not sure what I did but it is working.  Thanks for your help...

 

good job chasing the problem down!

and thanks for posting what you did.  it may help someone someday when they do a search for a tach problem.