CAV Air Conditioner control box

CAV Air Conditioner Control Unit Repair.

As you may recall CAV air conditioner began to falter intermittently about a month ago on CAV Mono #04. This is one of the first mono CAVs and the AirCon system was one of the early ones in the build cycle manufactured in South Africa by SMITHS. Unfortunately, I was never able to locate which applications (other than early CAVs) used it. CAV now uses another type unit and I do not know when the changeover occurred.
I was able to bypass the control unit (the gray box in picture #1) so it was clear the compressor, switches and wiring to the box were OK. I pulled the box and had it bench tested at an electronics shop and it was determined the voltage was getting to the small “sugar cube” relay but not out (the black box in picture #2). So it appeared the relay was bad. With help from the forum, I was able to locate a replacement, removed to the old one and soldiered in the replacement and everything now works as new.
The original relay was manufactured by HG part # HG4230 012 Z1CL. While I found several sources for these, they all only sold bulk orders.
There are several sources for the relay in the USA to purchase single relays that appear to match (if you have similar issues be sure to cross reference your individual part number to insure a compatibility match as your car/relay may be different!):

Mouser Electronics Mouser Electronics - Electronic Component Distributor part # 833H-1C-S-12VDC cost: $1.56 USD .ea
Digi-Key DigiKey Corp. | Electronic Components Distributor | United States Home Page part #PB337ND cost: $1.70 .ea

Long term, I plan to go to another control system where local parts availability would be easier but that will be a project for a winter month…

Excellent Veek! Glad to hear you solved it.

Thank you veek. Electronics problems can be so difficult to trace some times. I am very glad that you were able to figure it out.

Veek /Pat you never cease to amaze me with your persistance in fixing perplexing problems. Way to go.....

Thanks Veek, good information. Neither the heat nor the A/C ever worked in my CAV from the day I bought it, but I'll be looking into what's broken and needs fixing sometime this winter as a winter project. I'll be keeping this thread handy.

Thanks again.

Cliff,

First, check the fuse in a separate holder under the dash (not on the fuse panel by the A/C heater blower). It's for the climate control system. Then see if you are getting voltage to the purple&green wire going into the control box. If you are with the A/C on, the fan on and the thermostat turned clockwise, it may be the control relay I had to replace.
Also check and see if the wire bung on the hot water feed to the heater is connected. It's on the right side bulkhead. Mine was off when I first got the car. One thing I must say is that heater will roast marshmallows.
I have a couple of the sugar cube relays if you need one, just send me a PM or if you want to chat about it, give me a call.

Thanks for the efforts and positive results! Sometimes it's tempting to just ditch the offensive part and start replacing. In this case the answer, though elusive, was economical to carry out and non invasive to the rest of the vehicle. I will be printing off this posting and filing it with the other schematics and reference material. Thanks again! Cheers

Ian, before you go prime time, I have one small typo to correct. "If you are with the A/C on, the fan on and the thermostat turned clockwise, it may be the control relay I had to replace."
Should read, If you are not getting power to the purple green lead to the control box with the A/C on, the fan on and the thermostat turned clockwise, it may be the control relay I had to replace