Tacho Needle Permanently in the Red

SimonG

SimonG

New Member
Hello,

My 72 P6B's tacho has never worked in the 5 years I have owned the car. Now is the time to look at fixing it. The symptoms are:- needle fully at maximum in the red and never moves. I would appreciate any suggestions as to the best way to go from here.

The speedo needle is wildly hunting up and down too with grinding noises from behind the dash. I have to estimate an average of the speedo needle position to see how fast I'm going. Any assistance here appreciated also.

Cheers....Simon
 
Hello Simon,

I would imagine that your tacho has an internal problem, and as such an instrument repairman should be able to rectify the situation for you.

The speedo could also be in need or a general overhaul,..they do indeed seize and certainly in the case of my speedo a wandering needle and lots of strange noises eminating from within occured prior to silence and a still speedo needle even while driving... :shock:

It could also be your speedo cable in need of a good clean and some fresh grease, although I would imagine that your speedo also has its own problem. You could have both speedo and tacho serviced at the same time. New speedo cables are available, so you could also fit a new if you wished.

Ron.
 
Thanks Ron.

I'll have a look at taking the dash out and removing both instruments. Any tips re attacking the dash as I have never attempted it before?

Cheers....Simon
 
Hello Simon,

Glad to offer some tips, hopefully they will be of help... :D

To bring the instruments forward so as to gain access, you will see on your right a curved metal cover with a twiddly knob upon it. This will spring undone when pulled upon revealing two large flat head screws. At the other end you have two plastic knobs which adjust the brightness of the instrument lighting, and the speedo trip meter. Both knobs pull off which then allow the disk beneath to be unscrewed by hand. The metal cover can now be lifted away which will reveal another pair of flat head screws. Release all four and the instruments can be maneuvered forward. There are attachment screws at each end to allow the clear screen to come away. You will see the screws which secure the speedo and tacho in place and these can also be removed, but detach the speedo cable from behind first.

It is a tight squeeze to fit your hand in behind the instruments to release the cable, but once this is done it is somewhat easier to maneuver the instrument pod. Once you remove the speedo and tacho from their home on the printed circuit board, the wires from behind can be detached. Be sure to note their location prior to removal.

Refitting is just a reversal of the removal.

Best of luck,.
Ron.

P.S : How is the weather in Melbourne? Has been raining on and off for most of the day up here in Sydney... :cry:
 
SydneyRoverP6B said:
Hello Simon,

Glad to offer some tips, hopefully they will be of help... :D

To bring the instruments forward so as to gain access, you will see on your right a curved metal cover with a twiddly knob upon it. This will spring undone when pulled upon revealing two large flat head screws. At the other end you have two plastic knobs which adjust the brightness of the instrument lighting, and the speedo trip meter. Both knobs pull off which then allow the disk beneath to be unscrewed by hand. The metal cover can now be lifted away which will reveal another pair of flat head screws. Release all four and the instruments can be maneuvered forward. There are attachment screws at each end to allow the clear screen to come away.
Click to expand...

Not wishing to confuse things, but I thought the 4 large flat head screws with felt washers held the clear plastic screen on :?: :?: :?: and that there were 2 cross head screws that go through the spring panel on the right and 2 cross head screws next to the panel dimmer and trip reset holding the instrument panel itself on :?: :?: :?:
 
Hello Dave,

Yes you are right!!

I was going from memory, and I could picture the flat head screws in my mind, just put them in the wrong spot... :oops:

Still the locations I described are correct, just had the screws swapped around.

Thanks Dave... :D

Ron.
 
SimonG said:
The symptoms are:- needle fully at maximum in the red and never moves.
Click to expand...

Simon,
I had a similar issue a few years ago. Does the needle on the tacho rise as soon as the ignition is switched on? Mine used to rise, and then when the engine was started, typically reading 3000 rpm higher than actual engine speed. Removal and refitting cured the issue, seems to have been an earthing issue in the dash??? Worth a try.
Regards,
Dave
 
No, not a sausage. The tacho needle is actually jammed fully clockwise is the red zone. I pulled the dash out on the weekend and removed both the tacho and the speedo. This confirmed that the tacho needle has no free movement at all. The speedo on the other hand was suffering from wandering needle syndrome, ie at 60kph, it swung from 40 to 80 and I had to take an average (guess) of the actual speed. Cable seems ok, I gave it new grease. I've taken both speedo and tacho to specialists to get serviced.

Cheers
 
An update to close this one off.
Removed dash and hence tacho, speedo and speedo cable and took all to Howards Instruments in Heidelberg.
Tacho needed a new movement and was duly repaired.
Speedo was checked and found to be ok.
Cable inner was deemed to be RS so a new one was procured.
Fitting all three back resulted in smooth steady operation of both the speedo and tacho - fantastic!

Thanks to all for advice on this one.

Simon
 
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