Glow Plug Light on even tho I changed them.

The glow plug light came on in my 1998 Jetta. I changed the glow plugs but the light is still on. It started after I changed them and a lot of white smoke came out of the exhaust pipe. I drove it around the block, the glow plug light was still on, but it drove fine. The next time I went to start it (about 2 hours later), the car would turn over but not fire up. I should also mention that the wires in the glow plug harness are looking very old and worn.
Any ideas what the problem is and where I should start investigating the issue?
Thanks, Beth

Scan for codes, glow plug light is more than just indicator of glow plugs, it's more like secondary check engine light on TDIs.

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Welcome to the forums. Happy to see other mk3 owners out there.

Many things trigger the glow plug light.
You probably just did that work for no reason.
Your car will trigger a glow plug light if the brake lights have a fault lol, among other things it could be.
Scan for codes and stop throwing money at it for no reason (even though you thought you were correct). Gata love VW for misleading stuff like this. Been there. At least you have new glow plugs for winter!

your car (so is mine) has many things that will cause it to not start, and the 109 relay is one of those things that does not throw a CEL (maybe it does, I’ve been told now that it should but my 98 Jetta never once threw a CEL over the 109 relay issue.) there is a good thread around here for no start troubleshooting, you should read through it. Can't find the link right now but you can do a search easily.
You’re not a crazy distance from me. I am parting out my Jetta and wanted you to know I have some goodies you might be interested in, nothing engine related though.
Listing is here with pictures (CLICK ME)

As for your harness, that sucker gets really brittle, there is a good chance you have damaged it, it’s so freaking easy to do when you change out the GP or go injector work. You can wire them up temporarily; it’s just a connection at the top of each one so in a pinch you can rig it up if the harness is fubar.
Scan the car first. Have someone check your rear lights as well. there is a harness in the trunk under the carpet right by the latch area, if it gets wet, this will give you nightmares on tracking down the issue of why the lights work and done work, food for thought, dove me nuts for weeks trying to figure that one out. Anyways, send me a message if you’re interested in parts or just have general questions.

The key question is:. Is the glowplug light flashing or steady?

If steady, your problem is strictly with the glowplug system...could be relay or harness in addition to the plugs themselves.

If flashing, it's a "fix me ASAP" malfunction light with about 20 different causes including injection pump issues and problems with the brake lights.

In either case scanning for codes is a great next step...the ECU knows what's wrong and wants to tell you.

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mjez said:

Scan for codes, glow plug light is more than just indicator of glow plugs, it's more like secondary check engine light on TDIs.

Click to expand...

I think the only thing the glow plug light indicates that is glow plug related is when the glow plugs are actually working.

Somewhere in my "stuff" is a list of at least 12 items that can trigger the flashing GP light. The list was put together by MoGolf, I believe. The original list is somewhere in all these Threads in the forums.

As someone suggested, scan for DTCs....

Metal Man said:

I think the only thing the glow plug light indicates that is glow plug related is when the glow plugs are actually working.

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yea, when mine came on it was mid summer so i was like OH ill just blow that off, i don't need glow plugs right now. turns out the connection in the trunk was badly oxidized from rain water leaking in and my entire taillight and turn signals were OUT COMPLETELY. i had LEDs already and have a slow flashing relay installed so i had no idea. THEN I LEARNED, 1 fix it ticket later and a nice conversation with a state trooper at 2am about how my car was smoking, he got a healthy education on TDI's that morning, he was like WHAT you get 55MPG? i might have made a believer that night. but my taillights STILL have the same issue lol. you can see in my autocross vid how my left tail light is still bad. oh those days

ok im done my little story.

It should be noted by now that a glow plug fault will cause a check engine light, not a glow plug light.
Did I miss that in the above posts?

Not sure about the 98, but in my 2000 beetle, in addition to the glow plug light, the cruise control would not work if there were issues with the rear lights. So while waiting to find someone to scan your car, see if cruise works.