Weird interconnections?!?

[davidlp]

I know the computers in the B4 Jettas are connected to most everything, but...

One day I'm driving along and my cruise control kicks out and does not work again. At the same time my glow plug light starts flashing. After quickly pulling over and consulting the owner's manual, I discover that a flashing glow plug light is a fault inthe engine management system. Okay, strange to me, but I figure that hopefully the cruise going out is the cause and not an aftereffect, and the car is running fine otherwise, plus I'm over an hour from home, so I keep going.

And going... I live with this the next couple of weeks, no cruise and light flashing (okay, no bashing me), and then I get pulled over by a cop following me in stop-and-go traffic who tells me two of my three brake lights are out (lowers). I'm thinking it's kind of weird that two of them went and hoping nothing worse is wrong. I replaced them, as the bulbs were indeed bad, and when I started the car, for the first time in over two weeks the glow plug light doesn't flash and the crusie is now working! What the...

Obviously the computer was detecting the failed brake lights. You'd think the car could give me some more useful information that wouldn't require a trip to the dealer to read a fault code to tell me two $2 bulbs are out! And why take out the cruise?

Very strange.

 

[compu_85]

Flashing glow plug light can also mean you have a failed brake light switch. That will also knock out the cruse control. Did the dealer replace the switch for you? It's under recall.

-J

 

[whitedog]

Flashing glow plug light can also mean you have a failed brake light switch. That will also knock out the cruse control. Did the dealer correctly replace the switch for you? It's under recall.

-J

One little addition there. Little, but important.

 

[compu_85]

Very true. I'm kinda suprized mine did it right the first time

-J

 

[davidlp]

The only problem with that is that the brake switch was not replaced. I said it would be stupid to have to have the dealer diagnose it, not that they did. I diagnosed and replaced the two bad bulbs myself. I assume the high brake light would be on the same switch, and it didn't fail. So, again more strangeness, unless dropping the load from three to one bulbs fooled it.

 

[mtltdi]

VAG Com will pick up the failed switch error code. I bit the bullet and paid the $9 for it so I could D.I.Myself without having to leave the car there for the day.

 

[DaveBeatty]

I had same problem with my 2000 Jetta TDI. Flashing glow plug dash light and cruise control not working. Purchased for $12 a Brake Light switch from the VW Dealer. Same brake light switch that was due for a recall but had to wait a week to get into the VW dealer to do the install. Worked with a fellow TDI owner in Tacoma to replace the switch and both problems are history. Flashing glow Plug dash light is gone and Cruise control works again.

Thanks for the great advise from this Forum.

Note also used VIACOM tool to confirm brake light switch was failing. Note... no problem seen with actual brake lights ...