Searched....but didnt find what im looking for - glow plugs

[g-spec]

So I have a 95 TD golf....just rebuilt the head on it after a timming belt break......The problem I am having is the glow plug light does not turn off until I start the car.....I havent checked the relay yet....I might just replace it......
Car starts fine and runs great timming is set to 1.00mm, Im only worried about it cause its supposed to be my winter car....and I dont want to mess with it while I get deeper into school!!!!!

[bigblockchev]

There is no specific info in Bentlys but other glowplug systems that I have dealt with have a diagnostic feature which causes the light to come on when one or more glow plugs are gone. The easiest way to check them is to measure the amps at the engine connector which usually is a round twistlock affair attached to the head beside the drivers side end. there are a couple of larger wires red/white stripe which combine and go to the glowplug copper strip. you should get 32Amps if all four are working 24Amps if three 16amps if two and 8amps if only one is good. They can be tricky and look fine but are open circuited. The car will normally start fine on three or even two , mine even worked with one functional. The relay may have some way of detecting a bad glow plug and alerts you by coming on after the timing cycle is done. If you are actually getting current flow until the engine starts then likely the relay is toast. If you put your voltmeter on the glowplug bar and watch for voltage it should time out after 7 seconds or so after you turn the ignition on with the engine dead cold. If it goes much longer and doesen't shut off  it is likely the relay. Verify the plugs first though as they are cheap and relays are expensive. Cheers Dan

[Vincent Waldon]

Unfortunately VW glow plug relays are not that smart... at least pre-TDI.  The light itself isn't even that smart as it has nothing to do with power actually being applied to the glow plugs, but rather indicates one particular part of the timing cycle.

In any event, if its staying on until you start the motor the thing to check is if power is being continuously applied as well... the max cycle should be about 30 seconds and of course if it stays on too long the life of the glow plugs is shortened accordingly.  A test light or multimeter will tell the story.

If it's cycling fine then you can chose to buy schoolbooks rather than a new glow plug relay... that's very very likely what the culprit is.  Even with a bum temp sensor the relay should default to 30 seconds max.

[BlackTieTD]

if it is a relay at fault, grab a couple to try from a used car, part out, junkyard, etc... the dealer wants crazy money for those and i don't trust non-OE relays all that much.

[houseofdiesel]

According to VW, a 95 Golf td should have diagnostic capabilities with scanner (vag-com or 1551/1552 etc) you should be able to communicate with the glow plug control module via the port beside the ash tray (slide cover beside the ash tray). I have not been able to commuicate with an AAZ yet, but the dealer told me it can be done (this was during a warranty dispute over my brother's car, 94 Golf td that had a ten year/160k warranty that they offered back then). The glow plugs do run once the engine is started for up to 3 minutes on that model, so they do continue to receive power once the car is started depending on temp. Some models even have the glow plugs fire up when the drivers door is opened (might just be Passat though).
Check for power at the glow plugs, does it follow what the light indicates? If not it might be a bad instrument cluster internal issue, bad relay or control module, bad ignition switch etc.
Greg

[Hillshy]

i would say earth fault or relay fault,  the circuit as i understand it, basically decides what status the engine is in, ie cold or hot, this is determined by a coolent sensor, if coolent is cold, ths sensor doesnt ground one side of the relay, this fires the relay into action to power the glo plugs, if the coolent is warm then the reley does not energise and won't power the plugs.

if there is a break in the wire the connects to the coolent sensor then the relayand light will stay on for around 90 seconds and slowly burn out the plugs. So get it looked at asap IMO

so your circuit is kinda working, so bad earth or faulty sensor, maybe faulty relay.