[BradB]

My first post here but I've been lurking for a while.

I have a 1978 Shadow II that I got last summer and am finally catching up on some things I wanted to look at. When I got the car the AC did not work. I looked into that last year and the thermal switch was blown and eventually after some diagnosis thought the expansion valve (I believe that's what it's called) had failed and caused high pressures. That seemed like a spring project so here we are.

I replaced the expansion valve and the drier a few days ago and then today evacuated the system and recharged with R12a (I'm in Canada). The compressor works happily and pressures are good, so that was successful.

Oddly now the issue is that the fans don't seem to blow any air. Before (because the compressor wasn't running) the vents would blow warm air. Now, nothing but a bit from the defroster (in low, auto, or high). Defrost doesn't seem to do anything either. Has anyone experienced this?

I assume one of the handy ACU test boxes could assist, but I don't have one of course. I did see some old posts where someone had built one from the original diagrams - if the diagrams were available I would be happy to go that route and build one!

Thanks in advance,

Brad

 

[Jim Walters]

Hi Brad, welcome to the forum. The test box is needed to set the servo potentiometers but you can diagnose and test most of the operation of the system without it. There has been a lot of information posted here before, have you done searches to read some of the posts? The most common faults are the 44° sensor on the thermostat housing and the AC ECU ground connection on the passenger side of the transmission tunnel under the carpet just below the centre console. Check those first. Have you read through the testing procedure in the workshop manual?

 

[BradB]

Thanks Jim,

Yes, I'm working through those past posts, a lot of hits about recharging but I will look for those specific things and that will help me narrow it down, that's really helpful.

 

[Jim Walters]

In your search for 44° sensor there are thermostat housing images which will tell you which sensor on the housing it is. The test for it is to simply unplug it. This sensor prevents operation of the AC system until the coolant temperature reaches 44°.
Also when replying on a post you don't need to quote the previous one if you are following the train of thought in the post.

 

[Jim Walters]

The 44° sensor has sometimes been referred to as the 45° sensor so add that to your search terms.

 

[BradB]

So I’ve had some success! I think when I first tested it, the outdoor temp may have been too low and the system was reacting accordingly. I drove it on the weekend and when I got back in at one point it was quite warm and the AC turned on as you’d expect.

I still don’t think it’s right but it’s tolerable - sometimes it goes into a defrost zone for no reason. But, this will work and gives me time to do more diagnosis properly. Pretty sure the 44° has something going on since the fans fire right away, regardless of water temp. If I have a moment this weekend I’ll go at that.

Thanks for the advice so far!