Author Topic: Driver's Door Glowplug "Myth" (Read 3788 times)

vanbcguy · « **on:** May 04, 2009, 08:18:53 am »

We've all seen the "on some models glowplugs activate when the driver's door is opened" line in the manuals, but it's been generally acknowledged on here that it isn't true.

Well...

Got in my car the other day and was fiddling to find my iPod for a bit. Heard a "CLICK"... "That sounds EXACTLY like my glow plug relay" was my next thought. Turned the key on and no glow plug light - ie ready to rock. Fired immediately.

OK... So now let's actually test this...

Friday I came out to the car after work, opened the door and popped the hood. Stuck my finger on the end of a glow plug and yup, that sucker warmed up quite nicely. No key in the ignition, nothing more than "Unlock doors, open driver's door"

Well that explains why my glow plug light goes out so fast a lot of the time... It's already done!

This is on my Canadian '94 Jetta with a 1.6TD stuffed in to it in place of its factory 1.9, who knows if it applies to anything else.

MYTH BUSTED!

Vincent Waldon · « **Reply #1 on:** May 04, 2009, 09:30:22 am »

My light on the dashboard directly connected to the glow plugs confirms this behavior, although the engine management module must use a bit a bit of an algorithm, since it doesn't do it 100% of the time. For instance, if you open and then close the door several times in a row it won't keep firing the glow plugs arbitrarily.

My belief is that it's an AAZ in combination with MK3 chassis thing... discontinued by the time they started putting TDIs in the MK3... the engine control module being specific to the AAZ MK3.

My 2001 TDI (MK4) manual says "unlike previous generations of VW diesels, the glow plugs are no longer activated by the drivers-side door"

burn_your_money · « **Reply #2 on:** May 04, 2009, 09:40:47 am »

My brothers car (95 Jetta) had the glow plug driver door but it was disabled by the previous owner.

I thought I had read that it will only switch on the first time the door is opened and then after that it will stay off.

dieselweasel · « **Reply #3 on:** May 04, 2009, 10:26:23 pm »

I'm about to find out if mine has the glow plug door or not. Have installed a light on the dash and am going to wire it up to the glow plugs this week. I suspect that it does have this as well as my '93. Reason being, often when I have gotten into both cars when cold and turned the key to cycle the glowplugs, the glow plug light in the cluster would not come on. I would then cycle the key off, then back on, and the glow plug light would come on. Maybe the glow plug light won't come on when the driver's door activates them?

vanbcguy · « **Reply #4 on:** May 05, 2009, 08:39:46 pm »

That's how mine behaves - I've gotten in and turned the key on to see the light come on for a brief second, usually followed by me saying "you've got to be kidding!!" to the car and cycling them again. Now that I know what it's doing I've changed my behavior a bit.

All seems to be about how fast you turn the key on - if you jump in real quick and turn it on right away you'll get the light for a bit longer than if you get in, sit there for a moment, find you keys, etc.

As a side note, I've been driving my gasser for the past couple of days - fired it up for the first time in about 8 months, taking it up to give to my sister in Kelowna this weekend. Seems no matter how long I wait the 'CHECK ENGINE' light never goes out till I actually start it...

Vincent Waldon · « **Reply #5 on:** May 05, 2009, 08:43:24 pm »

In my dream world (filled with puppies and pixie dust) *everyone* wires a light on their dash connected to the actual glow plug buss... makes troubleshooting blown fuses and learning about bizarre driver's door behavior a breeze.

In my case it has prevented my wife from having to drive me to work twice: loose connection at relay, wonky temp sensor. :wink:

You'll also marvel at the duration of the AAZ afterglow, and perhaps even show your alternator some lovin' by not turning on the rear window defogger until the glow plugs are done. Or maybe that's just me needing to get a life. :lol:

dieselweasel · « **Reply #6 on:** May 05, 2009, 09:30:15 pm »

Haha. I'm doing it because I sit in my car for ~2 1/2 hrs every day. I need stuff like lights and gauges to keep me entertained.

Also a conversation piece for people who ride with me...I can impress the ladies with my glow plug knowledge :lol:

But you're right, it is a good diagnostic tool.