Top quality auto-electrician recommendation, please

[PMMatthews]

My car has been suffering an intermittent electrical fault over the last few years and it seems the mechanics at the local Porsche independent are unable to identify the problem.

I think it's time I tried a different tack, so I'm looking for recommendations for a really good auto-electrician, based in South London (as that's where the car is right now), please.

The problem manifests itself when the engine is hot (i.e. above normal cruising hot). After the engine has been switched off for a few minutes (say, to refuel), the engine won't restart. The usual ignition / warning lights come on, but nothing happens when the key is turned to the start position. After allowing the engine to cool down for 15-30mins, it will start normally. Once started, the engine runs fine. Provided the engine doesn't get abnormally 'hot', the car will always fire first time, even if restarting.

The usual diagnosis is a faulty starter motor - that's what I was told this morning, until I pointed out the garage had fitted a brand new one last year (a few hundred miles ago), when I'd been told that they had found and fixed the problem!

An immobiliser issue (it's an aftermarket unit that otherwise works fine) could be another cause, or a dodgy contact / wire somewhere which opens up when the engine is hot.

Seems to be one of those hard to identify (i.e. no fault codes generated), intermittent faults that mechanics hate these days, and it might just be more profitable to turn the focus on the potential electrical issues than keep fitting new parts.

Thanks

 

[T911UK]

Try Ed

[h1]Kent Car Audio & Security[/h1]11 Bromley Road
Beckenham
Kent
BR3 5NT View on map
[*]T: 020 8402 8881[/LIST]

 

[bernard tester]

It sounds like the crank position sensor there is only one on the 964 the older 3.2s had a speed and a refrence sensor side by side I always change the two, when it starts cold but not hot and then starts after its cooled a little I would go for that. Good luck.

 

[TonyGee]

I have the same problem on my 964, have had for years and had a new starter motor fitted which hasn't solved the problem. It's a real pain in this weather and I'm in South London too so lots of stop start to get it going. It's going for a service in a couple of weeks and that is top of the list and I was expecting another starter motor to be honest so maybe I'll get them (GT One, Chertsey) to check the crank sensor. How would that cause the problem, is there some degree of expansion and contraction going on?
Sorry I couldn't help solve the issue.
I'll let you know if they find a fix in 2 weeks.

Tony

 

[bernard tester]

The sensor is in a small ally housing and they get crushed, they work when cold and pack up when hot they will eventualy pack up all together

 

[mcgc0]

Berny (top bloke I met on a Milbrook shoot few years ago!) may have a point and will be something I might check out too. I have the same problem.

However, only when my 964 has been thrashed most the day (long sprint runs) or a long high speed drive in the heat (i.e. summer France autoroute trips) do I get exactly the same issue - non-starter until after a 5 to 10 min wait. But... a couple of times when I've stood outside the car, locked, imobilsed from the key fob then disarm and unlock, it all fires up again [stroking chin]. Never a problem with all-day normal runs up and down the motorway - only when hot days and/or really sprinted hard for a while.

What immobiliser are you using? Mine is an Autowatch product and I've thought of using the supplied code to completely disarm the thing for good and then see what happens. However, the crank sensor is a low effort and prudent check. How do I test this Berny or are they cheap enough to throw away and replace?

Marcus

 

[bernard tester]

Hi Marcus yes I remember the Milbrook day, on the sensors I just replace and on the older 3.2s change the two' the corrioson crushes them and I have often had to drill the old ones out , remember to set the air gap. Regards Berny.

 

[colin129]

I am not being funny, but this sounds like a simple DME relay fault, have you tried changing it, you don't mention it in the OP.

They used to cost £20 odd, but I think they are over £50 now.

 

[mcgc0]

I am not being funny, but this sounds like a simple DME relay fault, have you tried changing it, you don't mention it in the OP.

They used to cost £20 odd, but I think they are over £50 now.

Fair point. However, not sure why relay performance would be subjected to higher temps on some journey types if in a sealed box up front... Anything worth a go though, if it ticks it off the list.

 

[T911UK]

Sorry, thought you had done the DME relay. The relays run incredibly hot after an hour or so you can hardly touch it. Worth carrying a spare, they start at £15+

I have swapped to a solid state version after cutouts were experienced after 90 minutes or so of driving

 

[mcgc0]

Sorry, thought you had done the DME relay. The relays run incredibly hot after an hour or so you can hardly touch it. Worth carrying a spare, they start at £15+

I have swapped to a solid state version after cutouts were experienced after 90 minutes or so of driving

Now that is interesting, would never have thought the relay would generate so much heat during prolonged use - if anything i would have thought it more environmental. Are the relay contacts/arms in constant use every (milli)second or something..? Will definitely look into that it.

 

[PMMatthews]

Thanks all for the very helpful responses.

I have tried changing DME relay in the past without the problem going away. Besdies, I tend to think along the same lines as mcgc0 - while I get that the relays can get very hot in general use, it doesn't explain why the triggering factor seems to be a hot engine / engine bay (i.e. wrong end from front relay panel, no!?). Unless the heat around the ignition components could be placing greater strain on the DME? If so, why does it perform faultlessly in every scenario other then if I'm trying to start the car? The car doesn't misfire, stutter, cut-out etc.

Is changing a crank sensor a big job. Talk of drilling out old units makes me think this is a job for my (new) independent, once I've decided on one.

The aftermarket alarm is from Laserline. I did talk to them last year about this issue. They said they have never heard of one of their units suffering an intermittent fault as the result of being affected by excess heat. They gave me the name of an auto-electrician to try, who was based in Harrow. If I go down that route, I would prefer to see whether I can find someone well-regarded and local, if at all possible.

I'm gonna insist the starter motor is changed for another new unit under warranty, if the mechanic believes the one fitted last autumn is the culprit once more [] With a new ground strap.

 

[Dekker]

I've heard of problems with relays associated with alarm circuits. Relays that stick when very hot so they don't disarm properly.
Also of problems with crank sensor. I think Steve Brookes had issues with his when he owned his 964. He writes a blog under the name Boxey and owned a 964 for about 10 years.
He lurks on the 964RS forum.

 

[PMMatthews]

Thanks, David.

Not sure if I'm not right back at my original question, otherwise I could get into a game of component roulette.