Help and advice...?

Quick question...Installed a Viper 300 esp into a 97 Ford Ranger. Basic install, no keyless entry.  Well, about 6 months later the customer calls and says we ruined his trucks 4 wheel drive system! He says he took it to the dealer and they told him it was because of the alarm! He never brought the truck by for us to check. He just called and said we owed for the alarm AND the repair of his 4 wheel system or he's taking me to court. I just received court papers...

Any advice or help would be greatly appreciated.

Sorry to hear about that.  The dealer is looking for a quick escape (personal opinion)  The Viper 300 is very basic and should not cause any problems inside that vehicle. 

Check with the owner to see if the dealer even did anything to the car.  I imagine that the 4 wheel drive requires 12volts, so it could be as simple as a fuse or relay going bad.

What other indications does the vehicle have.

WOW, I'm glad I'm not in a country where every little thing that goes wrong, you can sue for ! Any way....... unless you tapped into the 2 nd ignition wire that usually controls most transmissions computers and fried the transmission computer and the 4 wheel drive system, you can pretty much blow this guy off. If the alarm had any affect on the 4x4 system it would have done it instantly, not over a 6 month period. Electronics do not take time to wear out like mechanical parts.

If this guy is serious, you can obtain maintenace records to see what this guy has all done to his vehicle and to blame the alarm for the 4x4 system is pretty harsh considering it has nothing to do with the vehicle when it's moving. Maybe ask him if all those times he went 4x4'ing through the bush could have caused the problem

How much does the dealer want for fixing it? Its its not to much try to sweet talk the dealer into giving you dealer labor price and just pay it or may be just do some cars for them for half off or something to cover it. I had an issue with a customer, he took his car to GM to fix at first they wanted 150/hour for labor from him, i went down and talked to them i got it down to 60. Just suck it up and pay it, if you just blow this guy off it might cost you more in lost customers.