7 replies to this topic

[kavesh]

Hi all

I purchased a Monaro gauge cluster a few years back for my ute. I want to now install in the van however, when I tested the tach, the needle does not move at all. I think it must be broken.

I have confirmed that there is a signal at the HEI tach signal on the dizzy using a multimeter, not ideal but at least I know there is a signal there.

Has anyone any pointers to try and figure this out myself. I do not trust service providers so want to have a go at it.

Thanks in advance.

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[hanra]

Does it need a tach adaptor?

[VDO]

Electronic ignition will typically put out a 5 volt tach pulse, compared to the 12 volt put out by standard ignition.  The circuit board in the factory tacho, while being a 3 wire setup, still won't see the 5 volt signal.  Need to upgrade the tacho circuit board for low signal input.  Should cost less than $200 to have done.

[kavesh]

Thanks for the replies.

 

I decided to strip the face plate off the tach to test the many diodes and capacitors and found many had no reading on my multimeter which was set to ohms.

 

I am based in South Africa so won't be easy to find someone locally to repair / upgrade my tach. 

 

I am thinking of looking for an aftermarket tach that has the same screw holes on the face plate which may enable me to swap out the internals onto my face plate.

 

Anyone done something like this before successfully. Any advice in this regard would be appreciated.

 

Thank you kindly.

[VDO]

The screw hole positions on the dial are standard VDO fitment.

Most VDO tacho movements will have this same spacing.

 

With yours, you'll probably find that the moving coil movement itself is ok and working.

It's the circuit board that can often fail in these LC LJ tachos.  Or as in your case, the circuit board is not compatible with your application.

Either way, you'll need a replacement board to accept the low signal from your ignition.  Replacing the tacho won't fix the problem.  This is a modern problem when using these old tachos in a later setup such as you have.  Other VDO tachos you find will still not see the low (5V) tach pulse signal.

 

The type of tacho circuit board you need isn't usually available to the public, only to Instrument Techs, so you'll need to see a Tech... sorry.

[kavesh]

Sorry to revive my old post.

 

I was chatting to someone locally who said that I should install a W terminal on my alternator. This would give out 6 volts for the tacho.

 

He was suggesting using a VDO tacho and we swap out the internals and use my original face.

 

Wondering whether this could work..

[VDO]

Sorry to revive my old post.

 

I was chatting to someone locally who said that I should install a W terminal on my alternator. This would give out 6 volts for the tacho.

 

He was suggesting using a VDO tacho and we swap out the internals and use my original face.

 

Wondering whether this could work..

The W terminal is usually the source of tach for diesel engines.  It's an AC output which needs to be converted to DC and to the correct pulse and voltage.  This still requires a specific circuit board.  It won't work directly with the tacho.

[kavesh]

Thanks for the reply VDO.

 

So what the guy (whose business is to repair instrumentations on more modern vehicles) said that we could adapt a VDO gauge that he had in mind. We would still use my original front, and mentioned that some calibration may be needed to get the gauge to read accurately. He just needed to see if he can get a 95mm gauge.

 

Btw, I am chasing another lead for Monaro cluster, hopefully with a working tacho. Hope to find out on the weekend if I can get it.

 

Then the big issue will be whether it will work normally with an HEI dizzy.