So it wasn't the starter motor...

[srichards]

After the non start when hot incident a few weeks ago I bought another starter motor. A whole £94 from autodoc.

It was fitted this week. 5 hour job as you have to drop the sub frame due to the usual 'bastard bolt' you can never see until you get in there.

Garage brought it round today as it was ready after the service and MOT. Dumbo here had accidentally flattened the battery on their loan car. Forgot to cancel the indicator so it left the park light on even though the light switch was on 0. I will never remember this is a thing. Oops.

So of course they go to start mine to move it and..... nothing. Same symptoms. Assuming it might be the starter something relay as the mystery ticking noise when hot is just somewhere in the right place. Not an earth either. They had started it and moved it and used it and it behaved every single time. It arrives home and then sulks instantly.

So on the upside my stupidity did at least make sure it didn't break down on me...

[Shoppinit]

Ugh. That's annoying.

There isn't really a starter relay*. It's done by the massive solenoid on the side of the starter.

What brand was the starter? Ridex? Unlikely the new one is also faulty, but can't discount it entirely since at that price it won't be an OE quality one.

It could be the ignition switch. To eliminate, I would wire up a manual override to the starter solenoid to send 12V to it, bypassing the ignition switch, to see if it turns over then. I'd use a pushbutton switch to close the circuit instead of turning the key to position III. If not, then it's could be a bad earth, a problem on the positive cable between the battery and the starter (including 200A fuse), or a feeble battery.

*I'm going to double check this in a minute.

[Shoppinit]

There's the J207 starter inhibitor relay. This only stops the 12V getting to the solenoid. It *could* be faulty, but I don't think you'd get ticking if it was. It's probably easy and cheap to replace though.

Only other thing I can think of is checking for corrosion / damage at the positive cable at the alternator. The juice goes via there.

[srichards]

It was a what looked like a reasonable remanufactured one. https://www.autodoc.co.uk/eurotec/8846173. Eurotec seem to have an ok name from what I can tell. RRP is nearly £400 but not sure what store you can set by that if it's been discounted to sub £100. Autodoc pricing is weird.

Shouldn't be the battery as that was replaced and it lives on a conditioner and it was the same with the jump pack on ie no start. It seems to be a heat thing. When it's hot it's not interested. Once it's cooled down then it's fine.

It's gone a bit Italian

[srichards]

Starter inhibitor relay! That's the thing they mentioned.

[srichards]

Got it started. PRND light was lit up like a christmas tree Banged into reverse, banged into D. Managed to not put it in the garage quite far enough forward so had to restart again. PRND not lit up like Christmas tree. Didn't bang into gear but did churn a bit before starting.

It's definitely not a happy camper at all.

[Shoppinit]

Classic F125

[srichards]

Classic F125

Good point. It was done quite a number of years ago so it probably needs another!

[HPsauce]

Classic F125 indeed, your dodgy starting symptoms are exactly what happened on my 2002 S8 a few years ago.
Fixed in the short term by taking out the J207 starter relay and putting a short circuit wire in. Longer term a new F125.

That's the J207 socket in my S8. The wire goes between the two smaller steel connectors (left and right in the picture) NOT the big copper ones!

[srichards]

Another order gone in to autodoc! Found the switch thingy. Gone for a Metzger as a reasonable brand.

[srichards]

Found this useful bit of the wiring diagram in the Bentley manual. Definitely where trouble might be intersecting.

[Shoppinit]

Yup. The signal goes via the F125 and to the J207 so it could be one or the other. Given that you're also getting PNRDS lighting up then that suggests that the F125 is faulty. I'd change both, to be on the safe side.

I've yet to fit my cheapo Chinese F125 and still get the PNRDS fault occasionally, especially after the car has been sitting for a while (which is often). I've found that cycling through the lever positions to "wipe" the F125 before starting helps.

[Shoppinit]

Classic F125 indeed, your dodgy starting symptoms are exactly what happened on my 2002 S8 a few years ago.
Fixed in the short term by taking out the J207 starter relay and putting a short circuit wire in. Longer term a new F125.

That's the J207 socket in my S8. The wire goes between the two smaller steel connectors (left and right in the picture) NOT the big copper ones!

This is good for confirming/eliminating the J207. skygtb's method is good for eliminating everything else.

[srichards]

Yup. The signal goes via the F125 and to the J207 so it could be one or the other. Given that you're also getting PNRDS lighting up then that suggests that the F125 is faulty. I'd change both, to be on the safe side.

I've yet to fit my cheapo Chinese F125 and still get the PNRDS fault occasionally, especially after the car has been sitting for a while (which is often). I've found that cycling through the lever positions to "wipe" the F125 before starting helps.

Will get the relay changed as well. Daft not to as it's got to be either original or at least 10 years old.

Didn't know about moving the lever to wipe the F125 trick.

They definitely sulk more if left don't they?

[Shoppinit]

Yeah, mine has been punishing me since I left it in my friend's garden for a few months when moving house. The F125 tantrums are from that. Annoying because it was an OE one I put in less than 2000 miles ago (and they're not cheap).