95 Caravan weak heater

I had the water pump replaced on my 95 Caravan. The heater worked fine until the water pump job. The mechanic checked the thermostat works fine but replaced it anyway with a 195 degree one still only luke warm air. He couldnt fine any problems heater hose in is hot out is cool. There is a switch/valve on the input side of the heater hose by the firewall. I was wondering if that could be the culprit does anyone know how to test to make sure the valve is woking properly? The cooling system is clean with so sign of debris or corrosion so I fingured the odds of a plugup are small.

"The heater worked fine until the water pump job."

That's what they all say.

Burp system, check heater blend door.

Thanks trapped air seems like a likely cuprit. Is there any standard way to burp the air or try to get it moving somehow?

If you had trapped air I believe you would have an overheat condition (I did). I warm engine up and with heater on and radiator cap off, I squeeze the upper radiator hose a few times with engine running and then pray. You may have a bleed bolt on the radiator side of the engine (diagram in Haynes manual) that will allow you to loosen the bolt and let minute amounts of coolant flow until the bubbles (air) stop flowing.

Thanks Ill try to purge air in the system. I replaced the water pump on my T&C air trapped in the system threw the temp guage off. I suspect air becasue I cant see anything else that would bring shut down the heat that quick. I cant picture that much air in there but has to be something like that will get on it before cold weather sets in.

Thanks guys purging the air increased heat about 60%, also found the switch on the core input hose by the firewall was stuck lubed visible linkage and I have enough heat to cook a pizza. Now Im ready for winter. Thanks!