Glow Plug Electrical Fault - Golf MKIII 1996 TD

**Mikejhan** · 13-09-2006,10:53 PM

My VW Golf Mk III 1996 Diesel Turbo will not start without help. I first noticed the problem when I tried to start it one day - The glow plug light came on then started flashing and then went off - the car would not start.

The 50A fusible link is fine and I know the glow plugs must be fine too as for the past two weeks I have been starting the engine by hooking up a direct electrical feed from the battery to the tip of one - I just hold it there for 10-20 seconds - engine starts and runs fine - Though getting embarrassing at work

I understand that it can't be the relay because when the GP light switches off I can hear a click. Is that right?

I read something about a controll module???

Please help me - I'm so stumped!

**thefoolmccool** · 20-09-2006,12:26 PM

Think Ive Definitely heard of this problem before. It is the Glow Plug control unit. (located under the drivers side dash). I had problems with my glow plugs but it turned out it was just a broken wire at the supply to the plugs. But everyone told me it would probablly be the Control Unit. Best to get it from scrapyard/breakers. I will look at the haynes manual later and see exactly whats involved in changing it.

**Mikejhan** · 20-09-2006,04:27 PM

If that is what I'm thinking of I was going to post a picture of that later tonight as I noticed it when I was changing the Glow Plug Relay (no joy - The original was clicking bought I'm clutching at straws

)

I did notice this black box hanging above the relays which has four black wires going into it and fixed in a row. I have just spoken to VW as I could do with getting it sorted straight away and they're gonna call me back so would be good if you could let me have further info. Think I might call the local scrap yard too!

Thanks!

**Mikejhan** · 20-09-2006,07:18 PM

Here is the image of what I was talking about - I'm confused because it says GP relay on here when the GP relay is located main relay board. I spoke to the VW dealer earlier and they said that this model 1Z does not have a GP control unit - I looked in my Haynes manual and only engine code 1Z has it.

So what is this then?

They recommended that try unplugging the temperature sensor as maybe that is damaged - Just trying to fin that now.

**stuart** · 20-09-2006,07:45 PM

Are there any numbers on it?

**Mikejhan** · 20-09-2006,08:08 PM

On there it say:

Part no 436-910

Doc no DPFK436961-0

I gave this info to the VW dealer but they couldn't even identify it.

**Mikejhan** · 20-09-2006,10:25 PM

Also if it gives any more clues, I recall that prior to this fault happening when I would go to turn the ignition to allow the coil to warm the GP light would come on then instantly go out and I would have to repeat the process once more and bingo it worked fine and the GP light stayed on for the correct amount of time.

**thefoolmccool** · 21-09-2006,03:30 PM

Right. Looked at the haynes manual - no help.

Firstly. The last problem you described is not a fault. On these cars the GPs are designed to come on either when the drivers door is unlocked or opened (can't rem which) which means less waiting time inside the car. So when you turn the ignition on less time than expected is taken to heat the plugs. So don't worry about this. It happens on my car too and the car starts no problem.

On my car, there is only one wire going to the plug closest to the gearbox. A bus bar then links the rest of the plugs. So a unit with four wires coming out seems useless. If you can check and see if you also have a bus bar and whether a wire is joined to the No. 4 plug.

But to control the process I have described at the start and the continuous heating of the plugs until the engine reaches operating temp, there must be a control module.

Also you could try this coolant temp sensor. Think it is located at the bottom left hand side of the engine as you look at it, in the thermostat housing. This might cause your symptoms.

Oh and if you have any ideas about gearbox oil, please check out my post!!!!

**Alun** · 24-09-2006,09:54 PM

Ive got a golf TD. In the cars manual it says that the glow plugs start to heat up after the drivers door has been closed. Which I thought was quite clever. Sometimes the glow plug light doesn't even come on (no it's not broken!) so it must be doing it's job.

For your car there should be a some sort of unit/module whatever under the dash near the fuse box (as mentioned before). You may have to take some of the trim off near the pedals to get to it (Ithink, don't quote me on that). If you locate it, could you not buy a second hand one from the scrappy and fit that?

**Mikejhan** · 30-01-2007,11:29 PM

Thought I should post that this was sorted. Thanks for all the help.

After trying everything myself and others could think of I called in the trusty old mechanic.

It turned out to be a wiring issue - So he ran a new wire from the relay to the plugs - Not sure if VW would approve of this fix but it works. I got charged £90 and was not happy but that was the price.....