Cerbera Tachometer Repair

[ajmevans]

My newly acquired Cerb has a tacho fault, the needle just dips a bit when you rev it, other lights in the gauge work fine. Is there a good repair guy? Any ideas? ...... Also going to need some new front discs soon, any recommendations appreciated.

Thanks

[morebeanz]

As a gross generality, electric oddities tend to point to a lack of oomph in the system, which can be caused by a failing 100 amp fuse or a battery that is no longer charging or holding charge. The cerb can be very sensitive to battery/electrical levels. I would do a quick health check on that first.

If your sure it's a dodgy guage, then most people go to Speedy Cables, who are effectively Caerbont who made many of the guages originally. You'll have to send it away, and they are often anything but Speedy...

[Steve_T]

There are a few tachos on ebay at the moment if you have the usual white dials. You could be waiting a while if you have the gauge repaired. I'd go with Ian's diagnosis, check the battery is being charged first as it's by far the most likely culprit.

[Gazzab]

Agree re 100amp fuse.
Regarding the front brakes...what calipers do you have / what size discs are there at present?
Have a look at some of brummies one piece discs (Search the forum) or if you have sep bells go for new AP's (possibly larger). dont go for the tvr drilled ones.

[sonnylad]

According to web site Brummies are also cross drilled

http://fortunamotorsport.com/products.html

[matty1275]

Had a similar fault with mine. It was quite erratic and dipped when I reved.
changed the big fuse and the holder and cleaned all the terminals.

that seemed to cure it for a while, but then I had an issue with the alternator.
fitted a new one and now all is good.
Diagnosis was probably voltage stabiliser in the alternator breaking down,
but the dirty terminals were making it worse

[pjnixon]

Agree again with the big fuse solution. I had mine do exactly that, then the battery wasn't charging. Replaced the big fuse (for £1.92 inc postage) and Hey Presto! A working Tacho and charging battery. Certainly worth parting with your knuckle skin for.

[crypto]

My tachometer had an intermittent problem, sometimes the rpm's are shown correctly then all of a sudden drops to zero until now when it failed totally. When I checked the connectors behind the dash, it became obvious there's a bad connection inside the tachometer. But how do you open the instrument ? The glass is held by the beading of the metal ring and it seems not repairable without destroying it ?

I cut a "window" into the side to peek in and found the problem to be the "loose" connection of a 470 Ohm resistor going to signal input (inside the tacho the yellow wire). Re-soldering the resistor solved the problem. The resistor can also be added outside, between +12V (green) and Signal Input (white/black). The tachometer type is "Caerbont Automotive EET5-1832-23A".

[TwinKam]

Blimey! Keyhole surgery! You did well. But how did you ensure that no debris entered from the cutting of the window? And how did you know where to cut, or was that just luck?
Instruments are more frequently opened up by gently teasing the crimped ring open, from the back obviously.

[crypto]

TwinKam said:

Blimey! Keyhole surgery! You did well. But how did you ensure that no debris entered from the cutting of the window? And how did you know where to cut, or was that just luck?
Instruments are more frequently opened up by gently teasing the crimped ring open, from the back obviously.

You can not 100% prevent debris entering the housing unless you work overhead , but I put 2 strong magnets next to the cut. Don't let the blade of the Dremel grinder go thru the metal, just until there is a tiny gap.
I tried to find a picture of an open speedometer in the web but without success. Knocking on the casing, the knowledge how long AMP connectors usually are and a some luck made the decision If the window cut wouldn't be successful, I would cut the instrument around the entire circumference.
Peter