B3200 Air Conditioner

The temp settings are sensed by the thermostat which has two wires going to it and is situated on the boxing/housing upstream of the heater core.
The pig tail goes onto the face of the evaporator to sense the temp.

It sound like the thermostat is sluggish and not reconnecting the two wires when cold. You can check these when it won't start. Only when the temp of the evap gets to near freezing does the thermostat open the wires connection and switch off the compressor.
Some times these are adjustable on older trucks and you may be able to move it both ways to free it up so it will work ok.
If no joy then possibly the thermostat may have to be replaced, not a hard job.

If the fans inside and out don't work the it could be a break in the fan resitors which are also mounted in much the same spot and usually held in the airstream with two small screws.
Inside it will have three resitors which control fan speed and also power to the rest of the sytem via relay. One of these resistor elements may be broken.
Again a relatively easy thing to check.

I would suspect either of these two items.

Cheers

Ross M

Hi Arthur

As advised elsewhere, a small fan heater will do a much better job and be cheaper to run. I doubt you air con will heat in sub zero temperatures, but the fan heater will heat your caravan effectively and quickly.

Motherhen

Arthur you air conditioner in your van will not blow warm air if below about 15 Deg C.

As soon as it gets cold we get a ton of phone calls from caravaners wanting their air con fixed..... as soon as they say fixed we "not getting warm on heat", the answer is "have you seen this problem before".

A refrigerated air conditioner on cool works by the evaporator (the part that get cold inside) pulling the heat out of the warm air that goes through the evaporator core (hot is attracted to cold... remember it) the heat that is pulled out of the air going through the evap core is then transferred by the refrigerant to the condenser that is mounted out side with it's own fan, the air flow going through the condenser outside then transfers the heat to the open air and the cycle starts again.... a refrigerated system is just a heat transfer pump much like how your radiator gets rid of the heat you engine producers.

An evaporator in a comfort type air conditioner can only theoretically run down to 1 Deg C before the water droplets start to freeze turning the evap core into a block of ice.

Most comfort type air conditioners will have the compressor cut out point set to about 5-10 Deg C, this is deemed as a safe temp to stop the evap core freezing in all conditions.

Now what has this go to do with heating?

Most refrigerated air conditioners that has a heat setting have what they call a refrigerant reversing valve, the refrigerant reversing valve does exactly what the name suggests, reverses the refrigerant flow in the evap and condenser.

As mentioned above where in a normal cool only system the evap gets cold and the condenser get hot.... in a cool/heat system when on heat the condenser pulls the heat out of the outside air and that heat is then transferred to the evaporator that in turn transfers the heat from outside to the air flow inside the premises.

The problem with this type of cool/heat system is the heat source is outside the premises and is usually colder then the heat inside the premises, seeing that the condenser (the part outside get cold when on the heat cycle) can only pull out so much heat before it turns into a block of ice, the lack of heat it pulls out equates to the lack of heat it can get rid of inside...... so if it is 10 Deg C outside it can only pull a maximum of 9 deg C out of the air (remember water freezes at 0 Deg C) before it cycles out.

It works by the amount of heat inside + the amount of heat that can be pulled out of the air..... if you work on the 9 Deg C as above and the inside of your premises was 10 Deg C you will get a temp of 19 Deg C..... still below the comfort zone of 24 to 26 Deg C.

If it was a 15 Deg C day it can pull out 14 Deg C of heat and the inside of you premises was 15 Deg C it can provide up to 29 Deg C of heating making it comfortable.

Most newish RV refrigerated reverse cycle (cool and heat) air conditioners these days have a electric radiating heating element inside the inside unit (evap) making the more comfortable in colder climates...... a lot of cars and trucks are going this way as well to provide heating inside until the engine temp increaser.

There is a lot more involved in refrigeration so I gave you a version that's understandable....... sure some one will get technical and try to out do this version.