Porsche 924 Scheiße - hit and run

[N Dentressangle]

Well, the electric window issue wasn't the plug - that's still happily in place.

There is an audible click from the motor when the switch is pushed in both directions, but it doesn't move. My suspicion is that the goosed weatherstrip on the window has allowed so much water to pour in that the motor's been drowned. I'd have replaced the weatherstrip earlier, but it's 55 quid!!! Ah well, more Porsche expense:

Left the dehumidifier in the car to dry the carpets out, and maybe the window motor'll come back to life too.

After that good long run I pulled a plug today to see how close the mixture was to being right:

Perfect biscuity brown - result!! I can take the 3mm Allen key out of my coat pocket now.

[rusty_vw_man]

1 hour ago, N Dentressangle said:

Well, the electric window issue wasn't the plug - that's still happily in place.

There is an audible click from the motor when the switch is pushed in both directions, but it doesn't move. My suspicion is that the goosed weatherstrip on the window has allowed so much water to pour in that the motor's been drowned. I'd have replaced the weatherstrip earlier, but it's 55 quid!!! Ah well, more Porsche expense:

Left the dehumidifier in the car to dry the carpets out, and maybe the window motor'll come back to life too.

After that good long run I pulled a plug today to see how close the mixture was to being right:

Perfect biscuity brown - result!! I can take the 3mm Allen key out of my coat pocket now.

Windows are irritating, but you must be pleased with that plug! 

[N Dentressangle]

22 minutes ago, rusty_vw_man said:

Windows are irritating, but you must be pleased with that plug! 

Very much so. Got an MoT booked next week, so it'll be interesting to see what the gas analyser says but I'm not expecting it to be too far out.

[dome]

My windows were troublesome too, I think I had worn teeth on either the motor or the regulator which would cause them to jam

[inconsistant]

This all sounds rather encouraging! Fingers crossed things continue to be settled.

[Verysleepyboy]

Really pleased you are making great progress on this one - love the colour as well!

Mine has become a lot more usable over the past months - I don't feel like it will break down each journey now - but have similar issues to you, despite being a couple of younger!

Rear window demister - nope, doesn't work, needs some investigating!
Intermittent wiper - nope doesn't work, needs some investigating!
Damp in the passenger footwell - yet again, needs some investigating!

A few other bits to look at, seats need attention, lacquer peel, cracked dashboard and could do with sorting out the excessively lowered suspension but it is great to drive as is and attracts a lot of attention everywhere!
 

[N Dentressangle]

20 minutes ago, Verysleepyboy said:

Really pleased you are making great progress on this one - love the colour as well!

Mine has become a lot more usable over the past months - I don't feel like it will break down each journey now - but have similar issues to you, despite being a couple of younger!

Rear window demister - nope, doesn't work, needs some investigating!
Intermittent wiper - nope doesn't work, needs some investigating!
Damp in the passenger footwell - yet again, needs some investigating!

A few other bits to look at, seats need attention, lacquer peel, cracked dashboard and could do with sorting out the excessively lowered suspension but it is great to drive as is and attracts a lot of attention everywhere!
 

Well hopefully I've helped with diagnosis on two of those three anyway. Suspect the wiper weirdness is pins not being pushed fully home in the connector block or similar. I have no idea, and if it fixes itself then I'll take that.

The rear suspension is raised and lowered on eccentric bolts. There are some OK write-ups on the net on how to do it. Mine was sitting lop-sided, so I raised the low side to the correct height again. Needs a massive open ended spanner - 32mm I think - but isn't hard to do.

[Verysleepyboy]

I'll certainly use a lot of your findings to help with diagnosis of the issues on mine, thank you! The joys of 40+ year old German sports cars!!!

With regards to the suspension - the issue is mainly around the cheap coilovers and late offset Boxster wheels that a PO decided was the right look. Not my personal taste on either front so will need sorting, but it's a big chunk of money for suspension, wheels and tyres that my piggy bank doesn't really support right now!!

[N Dentressangle]

I did have an FTP in Bristol yesterday - alternator was goosed so drained the battery over the few hours I was parked. Jump start from the Big Yellow Taxi saved the day.

Alternator now removed and at the menders.

[Matty]

4 hours ago, N Dentressangle said:

I did have an FTP in Bristol yesterday - alternator was goosed so drained the battery over the few hours I was parked. Jump start from the Big Yellow Taxi saved the day.

Alternator now removed and at the menders.

Small beer that though although inconvenient. Otherwise its took to the road well after the initial struggle. Obviously i was touching wood as i typed 😁

[N Dentressangle]

Last week I was in Bristol and came back to the car to find the battery was flat. I got a jump start then drove home, but noticed when I parked the car that the charging light stayed on even when I removed the keys. With the car running it went off as normal:

I suspected a faulty reg rec on the altermator and had this rebuilt - it needed a new regulator and a diode.

The charging light was on as above even with no alternator fitted. My assumption is that something is earthing through the alternator connection.

I have now re-fitted the alternator but still have the same light on unless I disconnect the battery. The alternator is charging fine. I have tried removing each fuse in turn but it makes no difference.

Any ideas?

[EyesWeldedShut]

How was the radio wiring when you were in at it? (I'm thinking it could be aftermarket wiring, inline fuse, spliced into the loom in an odd place?)

[N Dentressangle]

12 minutes ago, EyesWeldedShut said:

How was the radio wiring when you were in at it? (I'm thinking it could be aftermarket wiring, inline fuse, spliced into the loom in an odd place?)

Not too bad tbh. The car's had an alarm fitted at some stage but I haven't found anything too gruesome.

Seems an odd fault to suddenly occur.

[EyesWeldedShut]

3 minutes ago, N Dentressangle said:

Seems an odd fault to suddenly occur.

It's a proper head scratcher - I'd blame the alternator diode but it's doing this with no alternator even in the car 🤷‍♀️ Something is hooked into the exciter wire and pulling current - Googlefoo suggests a link through to the alarm system on some 924 models - there's a multiplug wiring diagram in that thread (but no clue if your alarm system is anything like the USA one)

[N Dentressangle]

Brilliant, thanks - I'll have a good look at it all later.

MoT this afternoon #prayforthe924

[N Dentressangle]

So, this just happened:

aaand...

Woohoooo!!!!

Now to fix that sodding charging light.

[rusty_vw_man]

Is the alternator trigger used to power up any aftermarket relays? I know it’s a favourite way of getting moody power source that’s only powered when the engine is running. Got a dodgy additional fuel pump relay, that’s a favourite bodge…..

[N Dentressangle]

58 minutes ago, rusty_vw_man said:

Is the alternator trigger used to power up any aftermarket relays? I know it’s a favourite way of getting moody power source that’s only powered when the engine is running. Got a dodgy additional fuel pump relay, that’s a favourite bodge…..

Could be, couldn't it? I'll have a look what that blue wire's doing tomorrow. But why it should suddenly act up now is a mystery - plus, it stays out if the car's been run for a while, but then comes on again!

[2316cc]

Well done on the MOT pass! You’re definitely winning!

I had all sorts of problems with flat batteries and the charging light coming on when I first got mine. It turned out the big fat wire(s?) that links the starter, alternator and battery is routed underneath the exhaust and had slowly cooked itself over the previous 30 years. I replaced it and it all worked again, but I remember testing it first by wiring it all up temporarily on top of the engine before swapping it properly. 

[N Dentressangle]

2 hours ago, 2316cc said:

Well done on the MOT pass! You’re definitely winning!

I had all sorts of problems with flat batteries and the charging light coming on when I first got mine. It turned out the big fat wire(s?) that links the starter, alternator and battery is routed underneath the exhaust and had slowly cooked itself over the previous 30 years. I replaced it and it all worked again, but I remember testing it first by wiring it all up temporarily on top of the engine before swapping it properly. 

Brill, thanks - I'm thinking it's something weird like that. I'll look into that first I think, as I did have the alternator out to fix its bushes last week so potentially buggered up the wire routing. That would also fit with the charging light being on even with the alternator removed.

[Rusty_Rocket]

Massive congratulations on the MoT pass!

I'm not sure what's causing the charge light problems, but I will say that a notorious 924 failure point is the alternator/ starter wiring that runs under the exhaust manifold.  It gets totally cooked from day 1, the wiring eventually goes crispy and sheds its insulation, causing all sorts of mad problems.

My car was really bad in this area; I removed both starter and alternator and remade the complete wiring loom up to the plug on the bulkhead.  Mine had bare sections of wiring close to shorting out and other wires touching each other where the insulation was gone/ melted.

Worth checking!

[N Dentressangle]

So, blue wire from the alternator up towards the bulkhead looks ok. Followed up to the multiplug above the brake servo:

Battery disconnected, the blue wire down to the alternator (LH side of the plug) has continuity with earth - should that be? I think it should.

I also have continuity between the blue wire and the fat brown wire which feeds into the red/black wires on the female side of the plug.

With the battery connected but no key in the ignition, I have 12v at the blue wire.

What shouldn't be happening is the charging light bulb getting power when ignition is off, but nothing when it's on. Weird.

[N Dentressangle]

I have spent a while* getting access to the wiring from the alternator up to that multi-plug. Although it looks undamaged, some fiddling and pulling on it has restored normal charging light service, so my suspicions are being confirmed.

It looks like a total bastard to remove, unfortunately - I've already bent back the heat shield around the starter and deleted its bracket with the angle grinder 🤣

[stuboy]

5 hours ago, N Dentressangle said:

deleted its bracket

permenent access 

[Zelandeth]

If the factory routing is a real pain, if you're likely remaking the loom in question anyway can you take a substantially different route?  A lot of decisions regarding routing of things in engine bays tend to be optimised for ease of mass manufacture, which you're obviously less worried about.

If you do route things differently though, do any future owners (or yourself!) a favour and document it properly!

[Asimo]

Is the alternator mounted via (insulating) rubber bushes? Common practice on VAG products of this era which could cause odd charging problems if the alternator earth strap is fitted wrong or corroded etc.

[N Dentressangle]

10 minutes ago, Asimo said:

Is the alternator mounted via (insulating) rubber bushes? Common practice on VAG products of this era which could cause odd charging problems if the alternator earth strap is fitted wrong or corroded etc.

Yep, rubber mounted. These were the old ones:

Replaced with a Mini shocker bush for the two rubber ones (which is a perfect fit) and a new exhaust bobbin for that mushy, horrible thing at the top.

Earth lead is good and properly connected.

I've ordered 2m of this in blue: https://ebay.us/m/p2pM5A so will make up a new exciter lead and route it more sensibly than Porsche did.

[N Dentressangle]

Down in Bristol again today, but luckily noticed when I switched off that the charging light came on.

Battery disconnected, so hopefully no FTP later. I'll be making a new harness then!

[N Dentressangle]

So, work commences on rebuilding the loom. The starter is REALLY inacessible - a right bastard to get at the wires on the solenoid, so I'd rather not remove stuff if I don't have to.

I started by pulling the alternator loom down from the bulkhead and snipping the blue wire off near to the multiplug so I can splice a new one in cleanly with heatshrink and it will all look original. I then (having removed the alternator) could pull the whole length of blue wire out to examine for faults:

Ah yes, that'd do it.

That burn is just after the wire goes back into the sheathing towards the alternator, and might have been caused by the wires heating up when the alternator shat its diodes and regulator rather than by exhaust heat. Interesting.

Plan now is to pull back that length of sheathing and re-insulate the +ive cables from the alternator. I can then feed the new blue wire through, put a ring terminal on the alternator end and splice the other end into the multiplug.

Next live report later...

[rusty_vw_man]

Always satisfying when you find an actual broken bit that you can fix!