No power to ECC

[RonMac]

FIXED!
I replaced with good, used ECC (Electronic Climate Control) unit from eBay (few weeks to arrive from Latvia).
The Part number must be correct - I tested Volvo Nos: 9171594 and 9134783 (Both work perfectly for S70, RHD,1998)
That explains why Scan tool could not read ECC fault codes (or even communicate with ECC) because "nobody was home" in the ECC.
Thanks abscate for your help with circuit testing.
This is a classic case of the obvious solution is the one that works (after wasting time with all the obscure and less expensive potential repairs).

[Porkyofthepine]

I made an account to revive this thread.

I encountered the same thing on my C70 and noticed it taking longer and longer before the ECC would would get power again and it would only last for about 10 minutes before losing power again. I ended up with the same solution of just buying another ECC unit off ebay but I'm looking to try fix the old one too.

I assumed it was a solder joint partly because of it working in high heat but also because my FM antenna is intermittently going out and sifting through forums seems to point to that being a solder joint. I've pulled apart the old ECC and I'm also not seeing anything wrong.

Any ideas on where I should look specifically on the circuit board or what else could cause the issue?

[RonMac]

Yes, I pulled my ECC apart too! But no solder joints look suspect. (The dry joints in the ABS control unit were more obvious. I fixed it). I looked at where the power enters the unit and saw nothing obviously loose or visibly overheated. So if you find the faulty location (in ECC) let me know because I will attempt to repair it before I throw it into the bin. I suspect that high temperature has destroyed a component such as transistor or capacitor). BTW, for S70, I have another spare, used ECC (tested - good) for sale, with Celsius metric numbers (for RHD - not sure if that matters).

[Porkyofthepine]

Yeah I've started suspecting capacitors or something else not immediately visible too. I'll probably test mine this weekend after I buy a capacitor discharge tool and will post an update.