pulsing dash...is it normal?

[m33ufo]

Whilst sat at a set of traffic lights, I noticed that the dash display was pulsing (slight change of brightness), with the engine note. Is this normal?

 

[chriscoates81]

Slightly different voltage as the engine revs maybe?

 

[m33ufo]

Yes, just wondering if it's indicative of a fault?

 

[Chris_in_the_UK]

Sounds like it could be the voltage regulator.

 

[richardjjs1]

Almost certainly the voltage stabiliser get it fixed it could start causing problems with ECU and the like

Sure RichardH will come back

Would think it will be expensive

 

[Richard_Hamilton]

I don't think I have heard of this before. The Durametric will display the supply voltage in the DME in Actual Values, so it would be worth seeing if it fluctuates there. You may also be able to see the supply voltage in Instrument Cluster>Actual Vales, but I'm not sure.

The voltage regulator itself isn't that expensive (£40-ish) if you DIY. There's quite a good DIY here: http://forums.pelicanparts.com/porsche-996-997-forum/408495-alternator-repair-regulator-replacement.html

Bosch Part number: F 00M 145 225 (Replaces F 00M 145 350).
Porsche Part No: 000.043.206.37.

I dare say it may be something else, like a bad earth to the instrument cluster, or a bad connection on one of the instrument cluster plugs. However, generally speaking, bad connections to the electronic units are pretty rare on the 996.

 

[Chris_in_the_UK]

If it's the regulator it's not expensive.

 

[m33ufo]

Much appreciate all your assistance.

 

[m33ufo]

Also noticed a slight undulation in the tail lights when at idle too. I guess that means I can discount any problem with the dash.

 

[Richard_Hamilton]

Try turning the light switch fully in each direction a few times. Perhaps it is a dodgy connection in there, which is a common fault.

 

[m33ufo]

The dash pulses whether lights are on or off. Once lights are on they pulse also as well as brake light when activated. They don't go on/off, just vary in brightness. Toggling the light switch didn't make a difference.

 

[m33ufo]

Also, just noticed, I had assumed only at idle but when rev'd to around 2000rpm the lights and dash etc still pulse.

Edit...and as I suppose you'd expect, ignition on but engine off, no pulsing to lights or dash.

 

[924nutter]

Occam's razor pretty much going to be the voltage regulator
Occam's razor alternatives alternator belt got oil on it in one place- drive slip drive slip, or maybe a high ish load continuously switching something like you think the heated rear window is off but it keeps chiming in then switchng off because it thinks it's at temperature then chiming in again

 

[Richard_Hamilton]

Did you do any voltage checks with the Durametric?

 

[m33ufo]

ORIGINAL: 924nutter

Occam's razor pretty much going to be the voltage regulator
Occam's razor alternatives alternator belt got oil on it in one place- drive slip drive slip, or maybe a high ish load continuously switching something like you think the heated rear window is off but it keeps chiming in then switchng off because it thinks it's at temperature then chiming in again

As you've mentioned some additional load, there is one other possibility. The previous owner (Rob Huff), had a couple of amplifiers professionally installed. Could these be causing the problem?

 

[m33ufo]

ORIGINAL: Richard Hamilton

Did you do any voltage checks with the Durametric?

Not had a chance today. Probably the weekend now.

 

[924nutter]

ORIGINAL: m33ufo

ORIGINAL: 924nutter

Occam's razor pretty much going to be the voltage regulator
Occam's razor alternatives alternator belt got oil on it in one place- drive slip drive slip, or maybe a high ish load continuously switching something like you think the heated rear window is off but it keeps chiming in then switchng off because it thinks it's at temperature then chiming in again

As you've mentioned some additional load, there is one other possibility. The previous owner (Rob Huff), had a couple of amplifiers professionally installed. Could these be causing the problem?

That is certainly worth investigating; almost like the amp is seaching for a signal and not finding one, or the bass speaker is just taking a big whack of current. Pull the fuses for the amp and see what happens. Are there great big F/O capacitors hooked up to the bass speakers? I have absolutely no idea what these do but perhaps their purpose is to smooth out the current demands of the speakers.

 

[m33ufo]

But, if it was the amp, wouldn't it be producing the same effect with ignition ON and engine OFF?

Still think it's probably the voltage regulator. I know nothing about the amp install so will investigate over the weekend.

Cheers.