1987 760 Turbo wagon heater all of a sudden wouldnt get hot and a leak appeared under the motor area. I found a broken heater water valve. I replaced. But befor installing, I verified that valve opened when I sucked on teh tubbing nipple. Now new heater valve in and my heater STILL doesnt get hot. no more leak. Took glove box out and checked the motor. Verified I get suction on grey tubing from motor to valve. I took motor apart and found NO dirt. I watched motor operate when climat control operated. damper assembly moves motor to various locations.

Any ideas why minimal hot air and no vacuum at heater water valve when heater is turned on?

Thanks in advance.
Brian

After replacing the heater water valve in the hose we couldnt get vacuum to the valve to open. After much troubleshooting we found that the vacuum controller valve located under the DASH behind the GLOVE box was also worn and leaked around that post. After discovering volvo wanted 620.00 for a new unit, I wrapped some PLUMBERS TEFLON tape around the metal post before reassebling. OK now! It's just a question how long the teflon tape will hold out.

Flapper doors may not be operating. I believe the under the hood heater valve should be open when your climate control system is off. Both hoses in and out of the heater core should be hot. When you ask for heat, it is the flapper doors that open and allow the heat to enter the cabin.
I had alot of heater problems with our 87 765T 205K miles. First I managed to clog the heater core with rubber sealant trying to seal the radiator. Had to keep back flushing the heater core to get it all out. Next I had to have the climate control programer replaced because the flapper doors stopped working and I had nothing but heat. This cost around $800, the part alone is around $600.

vacuum hose not connected somewhere?

Thanks, but we checked that. Inside the distribution valve, where there are several hoses attached, is there supposed to be an O ring or somethig to assist a tight seal?