BACKGROUND:I purchased a 1997 850GLT from a private party this summer with about 60,000 miles. It came with a remote starter which I believe was installed after the first owner purchased it (I am the 3rd owner). I had the dealer inspect it before making the committment. The only major fault detected was that the brakes needed replacing which I did (all 4). I also was aware that the clock/thermometer display wasn't functioning correctly. The thermometer was OK; it would always start up in Celsius, could be switched over to Fahrenheit, and seemed to be accurate. The clock was a different story. When starting up it usually began at zero although that was no guarantee that it wouldn't start at some other numbers. But it would keep accurate time, for instance if it started up at zero the clock would show :23 after 23 minutes went by. If I set the clockto the correct time it would maintain the correct time until the ignition switch was turned off and then turned on again. I haven't done anything with it because I felt that it really wasn't a necessity. I mention this because it may have some bearing on the following:
When the weather turned cold I noticed that adjusting the HVAC mode selector did not change the flow patterns (floor vs floor/defrost). The pattern did change when turned to any of the vent settings (note: this is a dual auto temp unit). I took the car to the dealer and he diagnosed the problem to be a defective ECC unit. This diagnosis cost me $500.00 (approximately 6 hrs. labor). My question: Is this reasonable? It seems that with all the instrumentation at their disposal and having certified Volvo Master Mechanics that the diagnosis could have been performed in much less time. Any opinions out there?
Also, I was told that the time/temperature display required a new circuit board.

$500 for a diagnosis is just short of robbery. Is the ign sw good?

$500 for an ECC diagnosis only or did they also replace the unit? $500 for diagnosis only would be a bit steep anywhere IMO but it's an expensive unit so I'd believe that price for both parts and labor.

$500 for diagnosis only. I believe the part costs about $600 so the total if I choose to have it repaired will be $1100+ plus instal labor.

Could remote starter installation cause the ECC to blow?

"Could remote starter installation cause the ECC to blow?"
-I can't imagine how it could as it's not related.

Did you already have to pay them $500? At our dealership, our normal diagnostic labor time for most things is between .5-1.0 hour, never 5 hours or more as no one would pay that. There's no way that it'd take any skilled, experienced tech trained in Volvos ECC systems 5 hours to come up with that conclusion. The car has a self-diagnostic system so it stores fault codes. One then only needs to diagnose the particular fault codes stored and if one is then left to conclude the ECC unit itself (VERY rare too btw), one can test that idea easily by just swapping one from another car if need be as that takes minutes to do (not hours).

If you didn't already have to pay, get another opinion. If you did have to pay them $500 and it's still not fixed, I'd ask to talk to their service manager as that sounds rediculous to me and I've been in the business for many years.

This is a remote possibility but it won't cost a thing to check. If the clock won't maintain time across ignition cycles and the temperature goes to default celcius, I would think that the cluster is getting power from the ignition circuit only not the battery. It requires both. Check all fuses.

This might be related to the HVAC problem ( and then again might not ). Assuming that the dealer is honest, and I usually do, the problem must be subtle to take that long to diagnose by an expert.

Good luck,
Greg