Rev Counter & Warning Lights Problem

[PMMatthews]

Headed out for a blast this morning, before settling down to watch the GP. I'd left the car on the drive overnight, instead of in the garage. It was a beautiful morning, and with the dew on the front and rear screens clearing as I started off, I thought I was in for a memorable drive.

2 mins down the road, the warning lights in the Oil Temp / Pressure guage flashed on momentarily as I dipped the clutch to change gear. A few minutes later, the rev counter needle died, though the trip computer display continued to work. Then nearly all the warning lights came on including the main warning [ ! ] light. I stopped and tried switching off / restarting. The rev counter flicked into life briefly before dying again. The warning lights lit up again after a few seconds. I turned for home, trying once more on the way to switch off the engine and restart. This time, just the main warning light came on after restarting, but the rev counter stayed dead. It remained like this for the rest of my drive.

Despite the various warning lights, the only obvious (other) malfunction throughout the whole drive was the rev counter.

I've tried the Streather book, but that only indicates potential causes of the rev counter failure (a problem within the rev counter itself, or loss of signal from the DME unit), and the 'xmas tree' effect with the warning lights (ignition system interference with the electrical wiring looms - though the car was serviced a few weeks back, including new plugs and tappets adjustment, this seems a bit unlikely). Unless I'm the victim of an outrageous coincidence, it seems more plausible that the various problems are related. I read in Streather that the Central Informer controls all the warning lights, so maybe this could be where the problems is.

I'm going to try again later on, once it's warmed up, just in case condensation is causing a problem somewhere. As I said at the start, it was cold last night, and I'd left the car on the drive.

Anyone experienced something like this before, or otherwise got any ideas what might be going on?

Thanks,

Paul

 

[colin129]

Paul,

I have to leave my car out all the time unfortunately. I drive it at least once a week, even during Winter, weather permitting, and I have taken the car out covered in condensation and I have never had any starting or running issues.

Whilst this probably doesn't help you very much, I would be surprised if condensation is the course of any of your problems.

 

[PMMatthews]

Colin,

Thanks for your reply. I realise that the car is robust enough to live outside all the time.

However, I went out just now to re-try it, and the car was fine again for the 30 minutes I drove it!

I tried before starting to reach the Central Informer under the dashboard, but could only just manage to wiggle a couple of rubber-covered connectors(?) at the front (towards the driver) of the unit, given how tight everything is up under the dash. Perhaps, that was enough to cure a dodgy connection, but I didn't know the Central Informer had any impact on the rev counter. Perhaps, someone out there can confirm?

I'll also check with my usual independent next week.

Paul

 

[PMMatthews]

Just had a quick chat with Bob at RGA. His quick reaction, without looking at the car, was that a drop in voltage due to a problem with the alternator / alternator belt could have the effect of causing warning lights to come on, and the rev counter to stop working. However, a one-off incidence isn't conclusive, and might instead just be a loose contact somewhere.

I'd still be pleased to know whether anyone else has had this problem arise with their car, and what the solution was. In the meantime, I'll check all the fuses and relays are properly seated, and check over connections under the dash, where I can reach them, before seeing whether this crops up again.

Paul

 

[PMMatthews]

The cause of my rev counter and warning light problems is starting to look like it's the rev counter itself. I'll put a final (please!!) post on here to confirm whether a replacement cures all the problems.

In the meantime, I've put a 'wanted' post in 'Members for Sale' as I'm looking for help finding a rev counter with OBC display (from a 964 or 993, RHD or LHD - they seem to be interchangeable). I've tracked down one or two with the well-known breakers but they seem quite pricey to me. Nothing in comparison with the new price of about £1,500.

Paul

 

[Steve Brookes]

Paul, I have a spare normal rev counter. I don't want to sell it but could send it to you to try out if you want one to use to confirm that it's the rev counter at fault? The alternative plug for the normal rev counter is hiding behind the dash. If your car came with the OBC version, the plug will be neatly tie wrapped to the loom. The reason I know this is that I took out the normal one and fitted an OBC version.

 

[colin129]

ORIGINAL: PMMatthews

The cause of my rev counter and warning light problems is starting to look like it's the rev counter itself. I'll put a final (please!!) post on here to confirm whether a replacement cures all the problems. 

In the meantime, I've put a 'wanted' post in 'Members for Sale' as I'm looking for help finding a rev counter with OBC display (from a 964 or 993, RHD or LHD - they seem to be interchangeable). I've tracked down one or two with the well-known breakers but they seem quite pricey to me.  Nothing in comparison with the new price of about £1,500.

Paul 

Paul,

I have been looking for an OBC for my Carerra 2 almost since I have owned it (coming up to 3 years) and the only ones I have seen have been at the breakers for £300 to £350. The only ones that seem to come up on E-bay are KMPH l/100km rather than imperial.

I have accepted that this is what I am going to have to pay unfortunately. At least I know who I will be bidding against if one does come up! []

I understand, and perhaps someone else can confirm this, that there is a company which can repair your faulty OBC/Rev counter. I will have a dig back in some old e-mails & see if I can find the info, but it may well have been deleted by now.

Colin

 

[PMMatthews]

Thanks for your posts guys, and sorry for the slow response. I managed to find a Rev Counter with OBC from a 993 at a breakers yeard for £85, but once connected up to the car it was clear the OBC wasn't working. By cannibalising parts from the old metric OBC, the independent was able to get everything working though, so I picked the car up on Friday night. All seemed to be working fine, only now with the bonus of an imperial OBC to provide speed and consumption data I can use!

However, a much anticipated drive on Saturday (after weeks of withdrawal symptoms) quickly turned sour when the familiar pattern of warning lights, warning buzzer, and failing rev counter returned to spoil it for me. Plus, there was now the added issue of a bad misfire. A second run on Sunday (I guess I was hoping some divine force might have taken sympathy on me overnight) confirmed the lights / rev counter issues, and the misfire situation had worsened to make the car pretty much undriveable.

So, back to the drawing board.......

Great tip on the non-OBC rev counter, by the way. These are much cheaper (£75 - 100 range on Ebay, versus typically £400+ for a secondhand OBC unit from most breakers, even without a guarantee of it being an imperial unit).

Paul

 

[Steve Brookes]

Paul, re-reading this thread, it sounds to me like you have the classic 'Christmas tree effect' which is an endearing term for lots of warning lights on. It is most often solved by changing the coils or the plug wires. This also seems to fit with your misfire. The coils are easier and cheaper.

 

[gazzy]

Don't know if this is relevant on Porsche's but having spent many years working on motorbikes I have quite often found multiple problems with electrics to be earth related.Usually if one problem occurs it is a component fault,any more than that I alway's look for earth.

 

[PMMatthews]

Thanks for the futher posts. Looking at possible causes for the misfire that could also lead to the voltage fluctuations which I think are triggering the 'christmas tree lights' seems to be the way to go. I'd wondered about the coils, so that's probably where to start. More to follow...