Originally Posted by Capt.Bill11
Open the control box that the pump is wired into. Check the fuses if there are any. If the system is set up where the pump only comes on if one or both of the compressors are running then you my have a bad triac. A triac is the switch that sends power to the pump when it senses that a compressor has kicked on.
If you have a system that uses a triac it's handy to add a bypass switch so when the triac fails you can bypass it and power the pump directly to run full time until you can replace the bad triac. It's also handy to carry a extra triac in your spares kit.
This jogs my memory. Both of our units suffered triac failures several years ago when the boat was plugged into a faulty shore power box and kept getting voltage spikes. I went to www.marine-ac.com
for some very good on-line trouble shooting help. If it's a later Cruisair unit with Triac switches, the trouble shooting goes like this...
Find the triac (roughly 3/4 inch square black block with three male electrical connectors...potted on a metal bracket with a screw on either end). Identify yellow, purple, and black wires and note their locations.
Disconnect the yellow wire. If the compressor keeps running, the triac is likely bad.
Now pull the purple wire (with the yellow still disconnected). If the compressor stops, but the fan keeps running, it is almost certainly a failure of the triac.
If you isolate the problem as a triac failure get the number off the switch. The one on our Cruisair is SANREX TG35F60. Go on line and find it at an electrical supply house. The cost will be about one third of what a local marine AC shop will charge. As mentioned above, buy a spare (about $9 on line).