Freightliner Classic Ac issues

Take a pair of vise grips and pinch off the heater hoses going to the cab and see if that makes any difference.

 

That’s right, passengers side, behind small panel, at the door. You can also access it by taking fuse box cover off. You’ll see water hoses running to it. A manual Solid steel cable from the temp control slider on the dash. If it’s bad, you can turn water valves off at the waterpump, 1 for cab, 1 for bunk. Also has 2 return lines, shut them off too, if you can. Doing that will tell you if the valve in cab is bad, if it solves the problem.

 

You may have a faulty blend door actuator. Meaning it is stuck on the heater core side and has closed off the ac side

 

The Classics don’t have one. Both cores are mounted next to each other. Air blows through both always. He says it’s blowing hot air. Has to be the valve.

 

Ok, didn't know that was the setup. I always shut my valves at the engine, as soon as the weather doesn't get too cold at night where I would need the heat. So there is not even a cable to control the blend?

 

There’s a manual cable, for heater valve, to open it or close it, attached to the slider ( cold, hot) control on the dash. That’s all. The blend doors are air operated. The blower blows through evaporator, first, then has to also go through the heater core, mounted side by side. So if the valves bad, heater core stays hot, air gets heated up, defeating the purpose of the evaporator. I always shut them off under the hood. I’ve had a new valve to install for a few yrs. myself. They only work good in spring and fall. I think they start leaking inside after about a year. I’ve seen brand new Freightliners that you had to shut the off valves under the hood, in the heat of summer to get the air to blow cold. Bunk valve works better, it’s electric. The air over electric valves, used up until 2000, on the bunk were a real disaster. WS had them on Cabs too, mounted on the firewall. They were a nice feature, setting them like a thermostat. But when those went bad, once the desired level of heat was reached, they would close, and air would pressurize the coolant, causing many unnecessary head gasket, head replacements, and Overhauls. Lol, a real dilemma. One minute everything’s fine, next minute, coolants spitting out the overflow. Idling with the radiator cap off, turn key off, coolant shoots 15 ft. in the air like a volcano. My 92 WS Cab valve did that. 6 Mechanics claimed I had a cracked head, before I figured it out. Almost got an Overhaul, over a $15 part.

 

Luckily I didn't have any issues like that when I owned a Freightliner. But it doesn't sound like the best set up to blow air through both.

 

It’s not a good set up, dust, dirt gets onto the evaporator, blocks the air flow for a/c and heat. But it’s a simple design. But not the greatest. Big Classic with no insulation, almost needs an extra a/c and heater. Condo Cabs just too big for the factory hvac

 

I agree, I kept the curtain closed to attempt to keep the cab area cool