Well, the heat stopped working in my 760, but I'm not sure where to start looking for the problem... I was always under the assumption that for a heater core to be bad, it had to be leaking (which mine isnt). Is that always the case? I'm suspecting the heater valve, but my car does have the electronic climate control, could it be related to that? Also, where is the heater valve located, and what is a good way to see if it is bad? Any other suggestions? Thanks for the help!
--
2003 Miata (53k mi), 1987 760GLE sedan (263k mi)

In addition to the other suggetsions, the heater core can become partially clogged. Feel the two hoses going into the firewall, if one is significantly cooler the core is clogged. I back flushed my core and it was a VAST improvement.
--
Paul NW Indiana '89 740 Turbo 120,000

DMC,

The heater valve is located in the engine bay on the driver's side firewall.
It's cut into one of the two heater hoses that goe through the fire wall. It should have a small vacuum line attached to it as well.

If your engine thermostat is broken and open all the time it's possible for it to prevent the engine from getting hot enought to produce much heat. Especially if it's really cold outside. Do either of the heater hoses coming out of the engine feel hot?

I'd suspect the heater valve if you are getting no heat at all.
--
Norm Cook; Vancouver BC; 1989 745T 210,000KM

Ditto on the heater valve.....A core will usually leak, or if it's completely plugged, you'll have to take the heater valve off to blow through the core anyways to check it, so plan on replacing the valve.

I found one at Canadian Tire (canada's original wal mart) for $30.00 or something. Pretty easy to swap out.

Get that Volvo warm!

Josh