Three problems related to defogger heater have been reported for the 1997 Volkswagen Jetta. The most recently reported issues are listed below.
It was at night rainy and cold. I turned on the heater and defroster because my car windows and whole inside of cabin were obscures by a fog. My defroster cleared the back window but all others not so I rolled down the windows and shut down the heater. I waited a while and used clothing to wipe the window. This was the third time in 6 weeks appx. I did turn on the fan alone to push brown fog out of the car. Today I checked my fluids the coolant was half gone in the reservoir so I topped it up. I saw on line vwof America has helped people in the past with a good will heater core but they told me 4-152004 that they would not help me. That is where I'm at no $ and I need my car for work. Thank you.
Replaced ignition coil for the third time in as many years!! electric water pump replaced. Eater core exploded a couple months later while I was on the highway at 65 mph with my child in the car! couldn't see anything as car filled with antifreeze cloud. Belt driven water pump went a week later. Entire power steering rack needed to be replaced. Window regulator needed to be replaced twice. Door handle broke twice!.
While parking my 1992 Volkswagen corrado back in late January 2005, my heater core leak all over my passenger floor, and had steam coming out the vents and fogging up my windows. After investigating on the internet I saw that this was a common problem on water cooled Volkswagens. On 7/30/05 I had a similar event happen while driving my wife's 1997 Volkswagen Jetta. The windshield suddenly fogged up and had steam coming from the vents and a coolant smell in the car. This happened while driving on the highway. I had to wipe the windshield with my hand so that I can see out the windshield. I pulled over and checked my coolant tank, there was a drop in fluid. What is in common between both vehicles is they are equipped with the same engine, the 2. 8l vr6. After researching again on the internet I have found out that the cars in NHTSA campaign id number : 92v050000 and most water cooled Volkswagen manufactured after that date share the same part number for the heater core. It seems that the faulty part is the heater core. Please investigate this, luckily there was not much traffic when my windshield fogged up, and no one was hurt. Thank you for your time.