1996 VW jetta alarm and heat

Could anybody help me figure out how to disable or temp. disconnect the alarm on 1996 jetta gls (manual ) when I want to replace the battery?
Also, I have a problem with the heat in my jetta,while the heat kicks in beautifully as the car warms up in neutral, heat decreases rapidly while driving and the hand on the dashboard goes to zero...
Do I have a bad sensor or something else?

Thanks,
1996 owner

I own a 96 Jetta and have found the same problem with the alarm. Mine goes off now when passengers leave the car. I think you have figured out by now, to shut it off that you insert your key in the driver's side and turn the key as if you were unlocking it. The alarm immediately will turn off.

Also, on the bad sensors, I recently had my O2 (oxygen) sensors replaced and it was worth the money because the engine light comes on now if a problem occurs. If you drive it into a VW specialist they can plug into a slot near the ashtray and tell electronically exactly what is wrong with your heat/ engine problem. Read your owner's manual and you will find something that looks like an outlet (I think with a purple outlet) where a mechanic can get a read on your problem. Also, change your battery out at Sears auto centers, if the key does not work.

Hope any of this helps.

There are several posts in this forum on how to disable. Perhaps someone removed or the thermostat is stuck open.