I have searched for this, but most of the posts relate to GP failure, and the resultant indications of the GP light staying on less. In my wife's 300D, the GP light has started staying ON, until the engine is started, at which time the light goes off.
The engine starts well, even with minimal glowing (10 seconds from cold = 15°C), glow is not needed if engine has run in last 1/2 hour.
Starting system is excellent, near new battery, good cranking speed.

Does anyone have any experience with this fault?

I shall start my testing tomorrow afternoon.
1. Test GP resistance thru the wiring to ground.
2. Current draw each, thru wiring loom.
3. ?

Is there a circuit diagram of the electronics inside the GP relay?

Is this a common fault (from what I read here it does not seem to be common)?

I welcome your suggestions.

__________________
Tony from West Oz.
Fatmobile 3 84 300D 295kkm Silver grey/Blue int. 2 tank WVO - Recipient of TurboDesel engine.
Josephine '82 300D 390kkm White/Palamino int.
Elizabeth '81 280E, sporting a '79 300D engine.
Lucille '87 W124 300D non-turbo 6 cylinder OM603, Pearl Grey with light grey interior


Various parts cars including 280E, 230C & 300D in various states of disassembly.

I bet you find a bad glow plug when testing the resistance.

Len

That seems to be as likely as finding the Holy Grail...

As far as I remember, the lamp 'ON' time varies by outside temperature. I have never seen a schematic with much more than an 'electronics go here' type of symbol for the timer in the relay diagram.

Perhaps this mystery timer circuit thinks it is really, really cold and keeps the lamp on continuously until started?

At one point my GP light would randomly come on while I was driving. I "fixed" it by replacing the relay and GPs with a post-glow type kit. I assume it was caused by a bad relay.

I was looking for the GP relay circuit, so I emailed Bosch (Aus) to try to obtain a circuit diagram from them.

The reply was:
> We would like to advise:
> Sorry, Bosch does not supply intellectual property information.
>
>
> Please do not hesitate to contact us again if we can be of further
> assistance.

It is amazing that a design which is 25+ years old is still considered "intellectual property"

Anyone have one?

__________________
Tony from West Oz.
Fatmobile 3 84 300D 295kkm Silver grey/Blue int. 2 tank WVO - Recipient of TurboDesel engine.
Josephine '82 300D 390kkm White/Palamino int.
Elizabeth '81 280E, sporting a '79 300D engine.
Lucille '87 W124 300D non-turbo 6 cylinder OM603, Pearl Grey with light grey interior


Various parts cars including 280E, 230C & 300D in various states of disassembly.

Perhaps it is time to sacrifice a unit, open it up, and document the design using 'reverse engineering.' The components inside should be easy to identify, and there are not likely any un-lableled 'chips' in there.