911 C4S starting issue

[mattb1972]

Looking for a bit of advice..

I have a 10yr old c4s and been having an issue in that it starts no problem first time when i get in to use it but if i pull over, turn it off and leave it for a couple of minutes it will either not start or really struggle to start( almost like a dead batttery) but if i leave it for an hour it seems to start no problem again....any ideas

[g7jhp]

Do you know the condition of the battery?

I leave mine on a trickle charger to keep it in optimum condition.

[mattb1972]

i tend to keep mind on trickle charge too but doesnt seem to make any difference

[David W.]

How old is the battery? They need replacing at 5yrs use in my experience. I’ve had it when they start the car ok but will struggle again unless driven for an hour or so. Old batteries take a while to charge in a running car that has other items consuming 12v power.
Hope this helps
DW

[mattb1972]

its about 3 yrs old so might look at replacing it, just seemed strange that it starts no problem if left alone for an hour but even after a decent drive if i turn it off the try to restart it it struggles....thx

[bgunn]

mattb1972 said:

Looking for a bit of advice..

I have a 10yr old c4s and been having an issue in that it starts no problem first time when i get in to use it but if i pull over, turn it off and leave it for a couple of minutes it will either not start or really struggle to start( almost like a dead batttery) but if i leave it for an hour it seems to start no problem again....any ideas

Starter motor, or corrosion on the Y lead that goes between the alternator, starter, and the battery feed coming from the front of the car..

[Marley71]

Most likely a corroded alternator cable. I had the exact same issue with my 997 gen 1. It is a cheap part but a tricky job. Well known issue with that age of car. Also it knackered my starter and had to get that replaced too.

[Jefferson Steelflex]

I always believe that on these cars these exact symptoms were the result of a dodgy crank (or cam) sensor? I’m sure I read that recently over at 911uk forum.

[R129 300SL]

Can confirm that changing the wiring harness on a 996 C4S cured this exact problem.

New part is slightly modified and has a 997 part number.

It becomes corroded and the resistance changes with high temps.

Tricky to do put definitely a DIY if handy with spanners

[anonymous-user]

This type of hot start problem is most unlikely to be battery alone - but rather the high resistance in the cable highlighted above - but a tired battery will accentuate it.