Originally Posted by Vincy
I have a National Tradewind LTC freightliner chassis and a cat engine. The dash air is no longer cold slowly decreasing. I think it might be low on freon? Where are the valves to fill the unit, what type of freon is used, and is there a manual on the air system??
Thank you for your time and info.
Find your evaporator, probably located under the front hood and look for a low pressure service valve near the evaporator. Probably a R-134 unit that you can top up with a kit from any good auto parts store. Wally knockers has them. After you gather your stuff, start the engine and turn on the Dash AC. On High with the selector in normal. Check and see if the condensor fan is running. Mine is also located in the front of my chassis. If not, you will have to make a jumper and jump across the low pressure safety cutout to get the compressor and condensor fan to run. Plug your refill adapter on the low side pressure fitting and read the pressure. If it is low, Not empty, squeeze the trigger on the refill device and add R-134, check the pressure again. If the guage reads no pressure then you should stop there and get a real AC shop involved. You don't want to ruin your unit. If the pressure come up a little remove the low pressure jumper you made and see if the condenser fan runs now. Continue to add R-134 until you achieve the proper pressure on the little guage on the refill kit. Somewhere in the green band on my unit. You should be wearing safety glasses during this entire operation so you don't get hurt. Gloves are also helpful. The amount of charge required is usually on a data plate on the evaporator housing. Mine is about 3.3 lbs of R-134. 40 ft. Freightliner Chassis with Cat engine. If you don't feel comfortable doing any of this than please seek help from a REAL AC shop.
Good luck and seeya on the road.