flashing door alarm light when starting

[pabinlove]

  hi has anybody had this trouble, car is hard to start very slow turn over changed glow plugs as 1 was dead, battery seams fine but am getting it dropped tested tomorrow, i have checked the alternator and it seams ok my meter was reading 12-14v i think, will check again to make sure. but i have noticed the red door alarm light flashing fast when turning over, when i have the car started it continues to flash then goes out after awhile,
I've been looking through some of the threads to find out but cannot find anything, i swear i saw something last week that it has something to do with the glow plug relay, but that maybe just be me reading a thread wrong
If this has been put in another thread then i'm sorry to post the question again
Any help is most welcome 

[Mirez]

The flashing light indicates the immobiliser is doing something or has a fault -

The key has a transponder chip inside it which is read every time its inserted into the ignition barrel - since the car will start then theoretically the key and reader are ok. The most common cause for poor starting with the earlier diesels is relay 109, specifically it develops cracked solder joints internally.

Later car's got fitted with a revised part which can still cause issues but it much less likely to develop a fault however pre 2002 cars often have the older, black 109 relay. You can test the relay on a bench or short its terminals in the box to prove/disprove its faulty however on the Galaxy its a bit of a pain to get to so for the sake of Ã,£10/15 I would get it changed. The part number is: 1J0 906 381A from VW/SEAT as its one of their parts.

Chris has an excellent guide to accessing the relay here: Guide to accessing relays

[pabinlove]

hi i've replaced relay 109 it's now a grey one the one i have removed is a white one. Starting seams to be ok but will see how it is in the morningto see if any more door light flashing

[pabinlove]

changed relay 109
struck up this morning very slow turn over, but fired up, door light did flash for abit then stopped, when idling it seamed fine no erratic behaviour, will get battery check again just to make sure.
When struck up later today again slow turn over but this time no door light.
I have checked the alternator for out put, but can you please tell or show me where to put the probe again just to make sure I'm not getting a false reading

[Mirez]

The easiest way is to measure across the battery terminals with the engine running and no loads on (ie no A/C, lights etc), 14.4V is the ideal and .4 +/- is acceptable. Next load the alternator by turning A/C, headlights and the rear defroster on and repeat the measurement - a good, fully functional alternator should load the engine accordingly and the voltage should still be around 14.2 - anything lower then 13.3(ish) and the alternators not working properly.

If you have an assistant turn things on then its normal to see the voltage dip below this threshold momentarily whilst it catches up.

[pabinlove]

thats great thank you