Chrysler Repair: 1998 van: theft system problems, chrysler voyager, electric scooter

Question
I have the above vehicle, about 2 years ago it started this problem... Sometimes when you went to start it, none of the instruments would come on, and it would turn over and run about 5 secs, you could do this 3 times and then, the next time nothing would happen. If you let it sit for about an hour or so it would be fine, this happened about 3 times over a year period. Oct 29th 2007, I was parked talking on the phone when the speedometer went up to 120. and back down to zero..it then shut off. It would not start, it was taken to my mechanic, who had it for 3 months, and said he replaced a relay/switch in the steering column, I ahd it about 2 weeks and it did the same thing, the next day he went to get and it started right up. but now its doing the same thing again....it has not been driven more than 5 times in the last 9 months, its been at his garage during that time. I was told to disengage the Factory alarm system, as it is causing the problem. Any ideas? And if the disengaging the alarm system would work..how do I do that?
Optional Information:
1998 Chrysler Voyager SE Expr 3.3L
PS
I was told to disenge the alarm system all I have to do is shut the doors, open the hood and unlock the tailgate with my key, also all the keys I have are aftermarket. The original was lost.I thank  you, i'm disabled and really need ny van to transport my electric scooter, to go to the grocery or anything else.
thanks again  

Answer
Hi RD,
You are probably correct that you can cancel the system from functioning by opening the hood and then unlocking the liftgate. However, after 20 subsequent engine on-off cycles the theft system will again begin to function on its own,  so you would want to do the same procedure again at that time and keep repeating that.
The system is integrated into the body computer and so you can't permanently disconnect it. You can avoid it's arming however if you will remember to never use the power door locks, the door keys, or the remote key fob when securing the van. Instead if you secure all the doors by means of the mechanical hand-operated push-buttons at the doors, then the system will not be alerted and so will not be armed to prevent theft other than being mechanically secured.
So those are two different ways to avoid being shut down by a false alarm. Normally just unlocking either front door using the door key should also cancel that, but if the wires from those switches or the switches themselves are bad then you have to try the hood/tailgate approach and/or avoid setting the alarm system.
On the cluster problem, should that occur again, you can prompt the system to do a self-diagnostic test. With the ignition off simultaneously press the trip and reset buttons, hold them in, turn the ignition switch to the run position, continue to hold the buttons and then after about 5 seconds the word CHEC should appear in the odometer window. At that point release the two buttons and allow the system to perform all its tests. If any 3-digit codes appear in the window subsequently note those numbers. If 999 appears there are no problems it can find with the system. It will also go thru three further separate "chec"'s which you should observe for any unusual behavior.
Let me know how this works out for you.
Roland