benja

This is a bit of a call for help…. My much-loved 150,000 1989 964 C4 has put me through it this last year. An engine rebuild due to broken head bolts, new set of tins, and a nasty engine management fault which took ages to diagnose and more means it’s cost me over £14,000 to keep on the road in the last 12 months. And now I have another 3 problems which I’d really like to fix cheaply rather than empty the rest of the piggy bank. After 5 years and 20,000 miles of pretty (ish) trouble free ownership the car is starting to be a bit of a money pit, and any ideas would be very much appreciated. The first one is clearly the most worrying…

Intermittent Brake Failure

A couple of times in the last 200 miles at random I’ve had the braking and transmission warning lights flash up and then lost brake assistance (though they have flashed up without the brakes going as well). The brakes just about work, but require a real stamp on them and I wouldn’t want to stop in a hurry. Looking on the forums, it sounds like a problem with the brake booster. But if I pull over and restart the engine, the problem goes away, and it’s all fine again. Brake fluid levels are fine, and I can’t see any obvious leaks from the booster, but a while back I did notice a load of liquid in the spare tyre well. At the time I assumed it was water from somewhere, but I wonder if a seal might have gone in the booster. But then again the off/on reset seems to solve the problem so is it just electrical?

Intermittent Electrical Failure

Sometimes when starting the car, it fires up but not all the electrical systems work. Radio for example is fine, but headlights won’t go brighter than sidelight level and electric windows won’t work. No warning lights and the car is driveable, but it’s odd and at night clearly an issue. A couple of restarts, and everything comes back to life (though not always first time). This happens perhaps 1 in 10 times I start the car?

Very Intermittent Heater Blower

This is the least of my worries, but is still a bit of a pain, especially in the current cold weather. The heater works, but the first time I switch the blower on it comes on for about a second, sounds horrible then cuts out, never to be seen again. I’m hoping it’s something fuse-like as I know the blower motors are expensive, and mine seems to still be working.

Any advice would be hugely appreciated. For the first time I've started to wonder if I should maybe consider letting her go....

fasterlaster

Lots of electrical issues? Check your grounds and clean them. Might even want to replace the main ground straps as well. I had a battery to chassis ground strap that looked good, but as soon as it was replaced some little gremlins went away. It's cheap at least.

ZG862

Take a good look at the earth lead between starter and body in particular. It lives in a pretty exposed place (unless you live in California) and corrosion eventually causes apparently random misbehaviour.

Z

spartansix

What voltage is your alternator putting out at idle and at 3000rpm?

Gordon52

Had similar issues with my 89,at times my windows failed to operate also.The shop could not duplicate the issues,for some reason a restart would temporarily solve ? On a hunch i replaced the ignition switch and all problems went away…Five years later and none of the problems have resurfaced ..Hope this helps.

benja

Its coming out at 14.7V for both.

I recently did a clean on the earth cable as well - stripped it, cleaned all connections and put everything back together and it seemed fine.

I did have a flat battery a few weeks ago which was unusual with no obvious cause, so did a proper bench charge on the battery which again seems fine now.

benja

Ignition switch. Interesting - i'll give that a try. Thanks!

Earlydays

If a battery goes completely flat and even if it then takes a charge, it may still be bad. This happened to me. Have the battery properly tested at a battery/parts store where they put a load on it.....

ToreB

Very Intermittent Heater Blower:
Failed rear fan. Try to set to minimum temperature. If blowers are working OK you have a problem with the rear fan resistor/fuse/motor. This is a common issue, see my DIY pages linked below for details.

Noisy blowers are mostly due to worn bearings, and the fan cage starts to rattle around in the fan housing. This is also often seen in the 964.
Cheers,
Tore

benja

Thanks Tore - much appreciated. I'll take a look at your DIY pages.

newsboy

If none of the above works, you might want to think about replacing your coils. A coil can still test within limits, and have an internal fault. Been known to be related to electrical issues.