Primus pump and wiring modification:

Since it is hard to find the original small primus pumps, it was decided to go with something a little more available.

The circulation pump used is a Groco CP-20-BBC ( like the pumps used on the older Birds for chassis heat. This pump moves 17 GPM and draws 5.5 Amps @ 12 vdc.

Electrical problem:
1. Origional wiring to a switching relay came from a power source, through a 10 amp fuse, going to the controller. Before the controller, another wire tap going to pin 30 of the switching relay carried the amps for the circulation motor.
2. The original pump motors are rated at 2.2 amps and the wire gauge was originaly installed for this amperage.
3. Since the new pumps draw 5.5 amps or better, it was decided to power them from a seperate power source and increasing the wire size to the switching relay to 12 ga to handle the increased amperage.

Solution:
1. Installing a 30 amp cb above the switching relays ( one for the front Primus and one for the rear.) (see photo)
2. Finding a clean source of 12 vdc from the house batteries, not start batteries.
3. Installing 12 ga red wire from 12 vdc source to cb then to pin 30 of the switching relays.
4. This wiring change will do two things;
a. Handle the increased amperage.
b. remove the motor power circuit from the controller, the original wiring retained for the controller.

Pumps:
Install the new Groco CP-20-BBC motor and brass pump with 3/4 inch in let and 1 inch out put to the existing coolant lines.

Overall soultion:
The new pumps are readialy available, have a higher GPM out put and brass direct drive pumps that are made for Coach heating systems.

Costs encountered:
Groco CP-20-BBC pump       $136.00
Wire/cb/miscl               $20.00
Total                      $156.00