87 maxima-no hot air from A/C

The blower motor inside the cab for my Climate control A/C stopped working beginning of winter 2008. The A/C was not used until today when the not operating blower was diagnosed. A bad Blower Motor Relay was replaced.

Had to have the FREON 134 recharged to make the A/C cool at all. Now that the Blower does operate at two speeds, and we do feel cold air, I found that when A/C system temperature is set to warm or hot, air from the ducts is not warm. The A/C compressor correctly stops when COLD temperature select is changed to warmer or HOT.

Opinion at the repair shop was that the heater control valve is not allowing hot radiator water to enter the heater core inside the cab.

Are there any tricks I can use to help the heater control valve again function correctly? Is the heater control valve easy to remove and replace or clean? Is it inside the cab or on the outside firewall? When the A/C system last operated before winter, A/C did heat and cool correctly.

Thanks for any help. Dave_s

87 maxima-no hot air from A/C Cabin air is blowing cold regardless of A/C heat setting. Remaining A/C functions seems to be working but I need to do the diagnostic test to be certain.

My 87 Maxima Service Manual indicates there is a 'diagnostic test mode' that I start by pushing a recessed switch on the A/C control box. Test results (fail or pass) are indicated on some indicator lights. On which unit are those indicator lights located? Are these test results lights the indicators on the A/C control panel?

Is the valve that allows water to enter the heater core called a 'Water Cock Solenoid Valve'? Is that valve located in the engine compartment at the firewall or inside the cab? Is this a vacuum or electrically controlled valve?

I am reading and rereading the Factory Service Manual.

Thanks for any help. Dave_ss