Rev counter problem?

[plymGTI]

Hi peeps, got a small problem with my 1989 Golf Cabriolet GTI. The rev counter on the car will only go as high as 4500 RPM (indicated) before the rev counter kicks in. I think that the rev counter itself is the fault, and the engine is in fact revving a lot higher then what the dial is showing as the car certainly picks up well and the revs are increasing although seem to take ages to do so on the dial, and only go as far as 4500rpm.

Has anyone else experienced problems similar to this before? Any ideas what needs to be done to fix the problem?

The car has been fitted with a TSR 1900 engine in 2005, performance cylinder head and an uprated cam - but I dont think these items would effect the rev counter/rev limiter on the car.

Also, whats the rev limiter of a GTI mk1/cabby.

Thanks 

[rubjonny]

hmm have the faces been replaced?

[plymGTI]

I am not too sure if the clocks have been changed as far as I can tell they are original although there are some gremlins with the warning lights and clock back light.

Im going to get the timing checked later today to make sure thats correct as I have already checked the rotor arm for a built in rev limiter, but it appears to just be a normal non-limit arm.

Cambelt was replaced earlier this year by the previous owner after the last one snapped - so perhaps it wasn't fitted correctly.

Just wondered if anyone has come across this problem before?

[rubjonny]

does it have an mfa?  if sao have a go at getting into the secret menu to bring up the digital rev counter.  another dirty test is to disconnect the wire to the high pressure warning switch on the oil filter housing, then rev the engine.  the buzzer & light should come on at around 2k rpm

[plymGTI]

Well very weird, when I refitted the rotor arm on the car it then revv'd normally, upto 6500rpm+.

Could a badly fitted arm cause the rev limit effect? Im a bit confused as to what was actually the problem, think I would have preferred to find an exact fault then it just cure itself. 

[rubjonny]

does the engine seem to actually rev higher or has the rev counter started to match the engine speed if you get me?

[plymGTI]

Rev counter now matches the engine speed....

[rubjonny]

hmm maybe summat is up with the hall sensor in thew dizzy, have a close look at the plug & wiring to it.

[bow]

yes i agree with that the hall sensor or in between the rev counter and speedo there is a 3 prong resistor called voltage stabilizer could be that good luck

[plymGTI]

Okay done some futher tests last night, and think Ive discovered the problem.

Whilst its daytime, all is well and good the rev counter responds quickly and freely and will go upto the redline on the dial.

However..... switch the headlights/sidelights on, and the rev counter itself drops down on the dial and this is when it will not read over 4000rpm when hitting the limiter, although I have done a further test driving along at 6500rpm and then put the lights on, the revs drop down to about 3500 indicated - any ideas what could be causing this?

I was thinking possible alternator fault? Dials themselves past it? Bad earth somewhere? All the lights function correctly, as does the switch as far as I can tell, no blown fuses or anything either.