Glow Plug Electrical Fault - Golf TDI Mk3 1998

[RichardP]

My VW Golf TDI MK3 1998 has an intermittent fault. Within a few minutes of starting out on a journey, sometimes the engine completely cuts out and all power lost (it only ever happens within a few minutes of a journey). I turn off ignition and turn on again half way to get Glow Plug Light (GPL) on. However, GPL does not come on (although all other red lights come on), and engine cannot be started. I turn off again and try again. After a number of goes, the GPL eventually comes on, and when it goes out, engine can be started. Journey, however long, can then be completed without further problem.
On occasions, after I have switched engine off having stopped, and then restart, same problem. No GPL, but after several attemps, eventually GPL comes on, then goes off, allowing engine to be started.
My engine is a AHU and GPL is NOT linked to door opening. Neither can engine ever be started without GPL first coming on, however hot engine is. Various manuals sugguest it is possible to start without GPL coming on, but this is not my experience.
I have replaced glow plugs, fuel filter and had diagnostics carried out (which revealed nothing wrong).
I have looked in haynes manual, which possibly points to Control Unit.
I would be grateful if anyone has any ideas :1zhelp:

[27motorhead]

Richard.

It'll be the 109 relay (glow plug relay / control unit) don't know VW code / part number - but happened on mine and is a known pain in the a*se fault on MK3 TDI's. Do a search in the forum for glow plug relay or something similar, but it sounds like it's that.

It'll be only about £10 - £15 from a VW genuine spares place including VAT. Don't ask me how much I spent as it ended up going into a VW dealer... £££'s!!!

Ta!

Tim

[Paul C]

Yep. Replace relay 109 (slot 3 from the left on the upper row of relays) ly it switches the supply for the ECU so when it fails the ECU does not register any new fault codes, just thinks the ignitions been switched off. Cost from VW £12.00 and mine hasn't failed since.

The ones to look out for are the old type black relays, prone to this problem. New type grey ones don't suffer the problem.

Paul

[RichardP]

Many thanks to both replies - can't wait to get out and get a relay, and hopefully sort this problem. Will let you know how I get on. Thanks again.

[RichardP]

Many, many thanks again to both replies. I have now had a new glow plug relay 109, grey, for 10 days, and not experienced the problem since. I'm quietly confident this is the end of it. I can't recall the last time I went 10 days without the car cutting out. The detail you provided was spot on. Thanks for the trouble you went to, to reply to my thread. Rich P :Blush: :Blush: :Blush: