We had a new air codititioner compressor put on last summer now that winter is here heater dont work I temp, control from cold to hot no change . Is there something they may have not hook up ....it was working very good before the work was done that was done first of summer

sounds like a faulty sensor

If the ac compressor is running and the line is cold, it could be a blend door under the dash that is not cutting off air flow thru the heater.

It sounds like the system is fried. Based on the description, it is just pulling in the outside air and not doing anything to heat or cool the flow. Unfortunately, this is a job for your preferred mechanic.

sounds like you have a bad temperature door actuator. This is a motor that connects to the door and uses inputs from the sensor in itself and the heater control module to open the door from hot to cold. I does take some knowledge on recalibrating this actuator and installing it. if it isn't install correctly it could damage the new part, so just take care

hi Planeman.
Why is the heater in my car not working? Ken Mattson, owner of Len's Automotive in Bellevue, Wash., says a car heater can stop working for a number of reasons, including: A low antifreeze/water level in the radiator due to a leak in the cooling system. A bad thermostat that isn't allowing the engine to properly warm up.11 Dec 2013

Why Isn't My Car Heater Working? ' Angie's List

https://www.angieslist.com/articles/why-isnt-my-car-heater-working.htm Search for: Why is the heater in my car not working?
Why is my car heater not blowing hot air?Hot coolant from the engine passes through a heater core, which looks and functions a lot like a small radiator, and a blower motor forces air through it. ... It's also the reason that a plugged heater core, stuck thermostat, or air in the cooling system can all cause a car's heater to blow cold.9 Jul 2017When Your Car Heater Blows Cold Air - Lifewirehttps://www.lifewire.com/when-your-heater-blows-cold-air-534667
How do you fix the heat in your car?Begin with the vehicle on level ground, engine off (cold) in park with the emergency brake set.Heater Controls. Step 1 - A heater cannot operate unless the engine is full of coolant/antifreeze. ...Refilling Cooling System. ...Engine Thermostat. ...Blend Door Actuator. ...Broken Vacuum Line. ...Heater Control Valve. ...Vacuum Gauge. ...Heater Core.How to Fix a Car Heater in Under 30 Minutes - 2CarPros
What are the symptoms of a bad thermostat?A motor with a bad thermostat will run fine for the first few minutes, then overheatrapidly. Other symptoms include the engine and radiator making a rumbling, gurgling, boiling sound: like a steam pipe knock, if you've ever heard one of those. A thermostat sticking open can make your heater not work in the winter.Auto, Car, Truck THERMOSTAT Repair bad thermostat symptoms
or go to this link if you need more help.
2008 ford ranger has heater that won get hot Google Search

that switch controls a vacuum operated door that lets a/c or heat thru.when accelerating,the vacuum in the engine changes so it sound like a vacuum issue.take apart the center stack and there is a vacuum actuator in there connected to the flap door .i have seen those have issues with the metal tab broken away from the plastic that moves it.is the a/c piping cold under the hood where it goes into the heater a/c assembly?the compressor should be cycling on and off and the pressure tested.

first check and if the thermostat is working. take it out put it in hot water. the thermostat should open up. also put a temp gauge in the hot water so you know at what temp it opens up. start there. dont forget theres more fuses under the hood for the ac unit

I had the same problem (during Summer!!) - If you take the Fan/A.C/Temp Control panel off, you'll probably find the plastic bracket that the control cable mounts to, is broken. I just used 3 zip-ties to hold everything in place. 30 minutes work, & 50c parts!! No problems since.

As me and my stepdad just discovered, the Galant came with an added feature to help the AC use less energy, by placing a heater valve within the dashboard. After pulling about 10-12 screws and half the dashboard apart, we simply opened the valve permanently. Many cars out there work that way all the time. Now after changing those lousy clamps into actual hose clamps by the firewall, my wife enjoys cool air in the summer and heat the whole winter. Hope this helps, there is a site that will actually show you a video of putting dash back together, as author did not film the disassembly.

You lost the Freon again, because you probably only fill up Freon last winter, you didn’t check the leak and fix it,

You have to check the AC belt, compressor, AC clutch, condenser ( see the small glass window to find out if there is some bubbling, if your Ac has bubbling, you need fill up Freon.