Thanks for everyone's input. It's been very helpful. Here is an update on the problem:
I wish I had the old pump, but unfortunately, the MB shop threw it away when they installed the new one.
First of all, I have tested the new pump and it works fine.
Second, I can get the new pump and climate control system to work, but it takes several tries of turning the car off and on, each time resetting some sort of breaker/circuit. Once the system is running, it will keep running until the pump shuts itself off when the system reaches the proper temperature. Climate control system then keeps working until the pump tries to come on again (under the start-up electrical load), at which time the breaker/circuit trips and the whole system shuts down. I can keep the system running indefinitely if I keep the temperature dial set to maximum temperature, thus keeping the aux. pump running all the time and avoiding the start-up load. The problem with that is obvious, TOO HOT!
Based on these findings, start-up load appears to be the problem. The operating load of the aux. pump is around .9 amps and the start-up load is 1.2 to 1.3 amps. This appears to be within the perameters.
This brings me to a couple of questions:
1. If the start-up load is normal, then could it be that the breaker/circuit is no longer handling the load? If so, does anyone know where this breaker is located?
2. Although the new pump looks similar to the old pump, it is lightly different. Could it be that the new pump draws more power than the old one did, thus causing my problem?
Input from anyone would be appreciated.