Volkswagen Repair: VW jetta door locks, vw jetta, vw jetta diesel

Question
I have a 98 vw jetta diesel in Alberta canada. When it gets cold I can not open the doors with the key or fob. usually the rear door will open but not the front. If its really cold -20 not doors will open either from inside or outside. Have to exit through the window. What could be wrong. The pump runs and stops but no action on the door locks.

Answer
Rui,
 Extreme cold will cause you many problems.  Condensation will form on mechanical parts, freeze, and render them inoperable.  Fluids such as hydraulic fluid and motor oil will change their pour rate and effect operations of the starter, as well as any hydraulic systems in the vehicle. Solenoids can jamb, and this can effect your doors.  The remedy, of course is to keep the vehicle in a heated garage (not a very helpful bit of advice for most people, myself included).  However, if you can arrange to park your vehicle under cover (carport,etc), it may mitigate the problem by keeping your vehicle out of inclement weather, and keeping moisture away from the components in question. Also, using a dry graphite as a lubricant for your door locks and mechanisms may be beneficial.  Hope this helps.  Jerry