13 replies to this topic

[CI 0308]

This has been asked before but there was never an answer given. My Original LX SS Tacho starts off reading ok but after about half an hour starts to read higher and higher until it sits around 6000rpm at idle. park it up over night start up the next day all is fine for half an hour of driving then the same thing happens.

I have replaced the voltage regulator with the Jaycar DC to DC regulator and set at 5 volts, soldered a wire bridge across where the selector switch usually goes. checked all wiring and all other gauges read fine. no the needle hasnt been painted etc. checked wiring through to negative side of standard style coil. runs an old school SBC with standard distributor.

anyone have any ideas as there isn't much more I can think of.

 

cheers Brett 

Edited by CI 0308, 01 June 2017 - 06:00 PM.

[VDO]

Circuit board is dying.  The components are changing values as the circuit warms.  Usually the resistors are fattening (increasing value) and the capacitors.

[CI 0308]

Thanks VDO. I'll pull it out and check it. Hopefully I can change out the components with a bit of luck. Or is there a better way.

Sent from my Redmi Note 4 using Tapatalk

[VDO]

Replacement circuit boards can be bought.  Or the internals can be replaced with the same from another particular vehicle.

[deauville]

 Dads  original untouched Feb75 built LH SLR/5000 did this  exact thing  "Gradually the tacho would read 1000rpm high then idle would be at 3500 then finally at idle 6000rpm showing and at the same time the neddle would be "EXTRA BOUNCY" .   It was a build up of HEAT that seemed to affect the tachos movement.

 

We put a coduit black plastic tube around the tan tacho wire near where it ran past  the wiper motor.This really didn't help much.

 

Often wondered why ,No one ever explained it to me.

[VDO]

Replacement circuit boards can be bought.  Or the internals can be replaced with the same from another particular vehicle.

You can try re-working the solder joints on the tacho circuit board, but it probably won't make much difference in this case.  The most common culprit is the choke (on the circuit board) which often becomes intermittent due to flimsy wiring and eventually just falls off the board.  It looks like a small puck.

[Rockoz]

I went through about 4 tachos about 10 years ago.

The choke had fallen off on all of them.

I did find a replacement choke from I think VDO in Western Australia.

But to be honest I reckon a replacement circuit board would be better than trying to fix the old one.

 

I think you do this dont you Chris?

 

I know there was someone doing it anyway.

 

Cheers

 

Rob

[VDO]

I went through about 4 tachos about 10 years ago.

The choke had fallen off on all of them.

I did find a replacement choke from I think VDO in Western Australia.

But to be honest I reckon a replacement circuit board would be better than trying to fix the old one.

 

I think you do this dont you Chris?

 

I know there was someone doing it anyway.

 

Cheers

 

Rob

Hi Rob.

Yes I do.  In my opinion, it's best to replace the circuit board.

I'm in QLD.

[Stevo75]

Hi Rob.
Yes I do. In my opinion, it's best to replace the circuit board.
I'm in QLD.

Hi VDO

I’m just fixing up my dash cluster and found the same issue you talk about with the tachometer choke fallen off.

I’ve attached a couple of photos below. I assume it’s the black circular piece at the bottom of the first photo.

Do you know where I can source a new circuit board from. I’m over in NZ, but guessing I’d need to get something posted from Aus.

Also, is there a way I can test the gauge cluster off the car. Keen to see what is working and what isn’t if possible.

TIA

Steve

Attached Files

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[VDO]

Hi VDO

I’m just fixing up my dash cluster and found the same issue you talk about with the tachometer choke fallen off.

I’ve attached a couple of photos below. I assume it’s the black circular piece at the bottom of the first photo.

Do you know where I can source a new circuit board from. I’m over in NZ, but guessing I’d need to get something posted from Aus.

Also, is there a way I can test the gauge cluster off the car. Keen to see what is working and what isn’t if possible.

TIA

Steve

Steve, you'll need an array of equipment to test the cluster.  A range of resistors, Waveform generator and a bench speedo drive and the experience to us them.  Not trying to sound like a smart arse, but that's the truth mostly.  If your tacho stopped working because the ridiculous ferrite choke fell off the board, just go to where the choke was connected and bridge solder those two points together and the tacho should work again.  The choke isn't needed for the tachos operation, it's only there to reduce line interference, but there isn't that much interference around that would mess up the tacho operation.  If anyone here needs a replacement tacho board specific to the Torana, let me know and I can order through my supplier.  The supplier won't sell to public, only to approved instrument techs, or I would direct you to them.  The part number is TC1020.

Edited by VDO, 16 January 2022 - 03:25 PM.

[Stevo75]

Steve, you'll need an array of equipment to test the cluster. A range of resistors, Waveform generator and a bench speedo drive and the experience to us them. Not trying to sound like a smart arse, but that's the truth mostly. If your tacho stopped working because the ridiculous ferrite choke fell off the board, just go to where the choke was connected and bridge solder those two points together and the tacho should work again. The choke isn't needed for the tachos operation, it's only there to reduce line interference, but there isn't that much interference around that would mess up the tacho operation. If anyone here needs a replacement tacho board specific to the Torana, let me know and I can order through my supplier. The supplier won't sell to public, only to approved instrument techs, or I would direct you to them. The part number is TC1020.

Thanks VDO

I’ll try bridging the wires where the choke was. Sounds like a plan. Those wires on the choke itself are ridiculously tiny aye.

How much are the new tacho circuit boards out of interest?

Cheers

Steve

[VDO]

Thanks VDO

I’ll try bridging the wires where the choke was. Sounds like a plan. Those wires on the choke itself are ridiculously tiny aye.

How much are the new tacho circuit boards out of interest?

Cheers

Steve

I'll call them tomorrow and get the current price, I can't remember it off the top of my head.  Maybe around $130.

[Stevo75]

I'll call them tomorrow and get the current price, I can't remember it off the top of my head. Maybe around $130.

Thanks again VDO

$130, that’s not too bad. Another quick question for you. I came across a couple sites mentioning that it’s best to replace the voltage regulator at the back of the gauge cluster with a new style aftermarket one. What is your experience with that.

Cheers

Steve

[antelopeslr5000]

Thanks again VDO

$130, that’s not too bad. Another quick question for you. I came across a couple sites mentioning that it’s best to replace the voltage regulator at the back of the gauge cluster with a new style aftermarket one. What is your experience with that.

Cheers

Steve

It can't hurt while the cluster is out. The old voltage regulator is a bimetallic type and can lose accuracy over time, affecting the accuracy of the quad gauges. A solid state voltage regulator will be more stable.