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240 AC Controls

volvowagoon

Active member
Joined
Jul 19, 2012
Location
Franklin, IN
Hey guys,

I'm trying to get a head start on repairing the HVAC issues in my girlfriends 240. I actually started thread about wanting to get the AC working months ago, but it didn't quite pertain to the issue I'm addressing here. I'll update that one once I can deem my electrical system good-to-go.

What we are noticing is that the blower motor runs in all speeds just fine, but also runs on low speed in the off position. Upon further inspection I noticed that the compressor clutch is also on at all times. Nothing changes if I move the thermostat into any position, so something isn't working right.

I generally hate diagnosing wiring issues in old Volvos now. RIP volvowiringdiagrams.com. :-(
However, thanks to cleanflametrap I have this nice simple drawing. I think I can trust that he has it drawn correctly.
w1HvHr3.jpg


First of all, let it be known that we did not drive it long with the AC clutch stuck on. I unplugged the pressure switch pronto because I'd like to continue using this compressor some day. If I study the diagram, it would appear to me that the t-stat is stuck closed and allowing power to the relay and therefore those two malfunctioning circuits. I've never done one of these, and they're kinda funky so this will be an interesting adventure.

Does my diagnosis sound correct to you guys? Thanks. I'll post updates.
 
The usual reason is the thermostat is bound up and you need vise-grip strength in your index finger and thumb to shut it off all the way. Pulling the plug on the low pressure cutout switch has the same effect on the compressor, but not to shut off the blower low speed.
 
Oh dang... so there's an indent to get to the off position? :lol: Okay, I'll have to try that and go from there. I saw a video of a guy that does something similar to whats on your site except he keeps the thermostat. Can I bypass the microswitch with a snowflake switch and keep the temp control? I'm not sure if it's really necessary to keep it since the the heater control will kinda give the same results. Right? The compressor would just run more than it need to with the thermostat removed. Right? This system is kinda wacky.

Thanks for the info!
 
Last edited:
... I saw a video of a guy that does something similar to whats on your site except he keeps the thermostat. ...

I kept the thermostat too. The Microswitch was the problem, if I recall correctly. I didn't want to replace the thermostat because I'd have to dig the cap tube and sensor out of the butyl around the evaporator, so I just left it in the circuit behind the panel.

http://cleanflametrap.com/ac.html
 
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