* When the engine overheats, the cabin heat (AC) will not work, it blows cold air only (but it works fine at other times)! I feel this is an important fact in the diagnosis, it seems to me to indicate that the coolant has stopped circulating for some reason. You're correct that this is unusual and ...

I'm unfamiliar with SPA Volvos... is there a temp gauge in the instrument cluster? Either oil or engine temp.

I'd probably push a little on the Volvo dealer service department. Try to make it their problem, talk to the manager -- polite but firm.

240 is hot, yes.

Let me see if I can summon a guy with SPA experience to this thread...

Was the coolant temp sensor replaced? I read you replaced much of the cooling system, but didn't see mention of this. The way the HVAC stops heated air during your overheat is super odd and not a behavior I'm familiar with at all. It does sort of sound electronic in nature. Usually this symptom migh...

Thinking the temp sensor, check a hose under the hood with an infrared temp gun both before and after issue to ground truth your onboard temperature measurements. Can get an infrared temp gun at Harbor Freight pretty cheap.

I have read about this problem and I am having the same problem with my XC90. The problem is a short in the ECM. Apparently you can get it repaired or replace for $1000.00 and up. I will post the link to the site. Hi, are you able to share that link? I've got one that seems to be having the same is...