New to me Dynasty blows hot air only in A/C.

[Wanderlust]

I recently purchase a 2002 Dynasty.  It was pretty cold out when I tested it and it seemed like it was working. On the way home from purchasing I realized it is blowing only hot air.  So far I have figured out the compressor is doing its job and it is good and cold on one side of the evaporator.  I can hear what sounds like a door opening or closing by air action in any of the mode positions for where the heat/air is pushed i.e. defrost, vents, floor, etc.  There are no similar noises when switching to ac mode.  I am inclined to believe the issue is with the water valve on the firewall behind the generator.  Is there a way to check voltage at the valve connector that will tell me the valve is getting the proper open or close signal?  They are pretty small pins so will have to figure out how to get a meter lead on them.  I want to avoid getting inside the dash if I can.  Also if I find it is the hot water valve, am I likely to dump a bunch of coolant or just the contents of the heater core when I change it.  Last question, is there a separate fuse for the heater control different than that of  the blower which works fine.   Thanks in advance. If I'm way off base in my troubleshooting, please straighten me out.  

[Ivan K]

There are major differences between models and years. Pictures of the valve, the controls, hvac box above the generator would give you better chance to get answers. I know my system but it could be very different yours. 

[Rodger]

A quick check to assure the heater valve is the culprit is just pinch off one of the hoses somewhere to stop flow. Luckily I have never had to work on this system, I wonder if they have blend doors like later model autos?

[Wanderlust]

Good idea Rodger.  I'm taking it for a drive tomorrow and will clamp off one of the hoses and see what happens.  I'm glad that at least the system is producing cold.  I just have to figure out how to get it out.  Thank You.  

36 minutes ago, Rodger said:

A quick check to assure the heater valve is the culprit is just pinch off one of the hoses somewhere to stop flow. Luckily I have never had to work on this system, I wonder if they have blend doors like later model autos?

From what I have been able to gather, it sounds like on a lot of coaches the air is blown past the heater core and evaporator simultaneously so the water valve does all the work of metering the temperature.  I will find out tomorrow if it's the culprit when I clamp one of the hoses off.  

[LakeBob]

This may help give you an idea of how the system operates, assuming yours is similar. Regardless, a great post with a lot of valuable information regarding a typical chassis heat/ac system. 
 

https://www.monacoers.org/topic/6608-working-on-a-mh-is-kinda-like-spitting-in-the-wind/#comment-65925

[vito.a]

I installed a manual hot water shutoff on our Windsor.  The heater hoses are up front above the generator.  

It really helped the dash A/C. 

Good luck with your new coach.