usrjcro11 Posted August 29, 2016 Share Posted August 29, 2016 The truck started spewing freon out f the dryer bypass valve. After about 5 years from doing an AC overhaul.Thought it was stopped up ev. Since I was going to replace ex and dryer decided to replace AC compressor also. I also replaced the low side line from the ev to the compressor. I flushed everything while I had everything disconnected . Pulled vacuum and let it set overnight no leaks. Put one can of freon in and low side went to about 18 and high side to 150. Temperature outside was about 85 degrees . Put another can in and low side went to about 25 and high side went to 300. Did not it anymore in. Was thinking about putting a new condenser on it. The AC evaporator is cool but not cold. With the high so high am I wrong thinking the condenser has some partial restrictions? I took the side panel off the evaporator and blew it out. It was pretty clean. Any deals? Thanks ahead f time. Quote Link to comment https://www.bigmacktrucks.com/topic/46614-1991-mack-ch613-ac/ Share on other sites More sharing options...
br549 Posted September 1, 2016 Share Posted September 1, 2016 CH should hold 3lb for a day cab and 3.5 lbs for a sleeper cab. Is the engine fan kicking in, it keeps the pressure down by cooling the con denser. The high pressure switch should cut the compressor off before the pressure get too high to blow off the drier valve. Quote Link to comment https://www.bigmacktrucks.com/topic/46614-1991-mack-ch613-ac/#findComment-344240 Share on other sites More sharing options...
BGarofalo Posted September 2, 2016 Share Posted September 2, 2016 Change the expansion valve an charge it to the correct weight and you should be good. Condensers don't typically become plugged up internally. Quote Link to comment https://www.bigmacktrucks.com/topic/46614-1991-mack-ch613-ac/#findComment-344291 Share on other sites More sharing options...
usrjcro11 Posted September 3, 2016 Author Share Posted September 3, 2016 I replaced the fan clutch Wednesday. The clutch came from Mack. I only have less than two 12 ounce cans f freon in it with high pressure over 300 and low pressure around 25. The expansion valve, drier, and compressor new from Mack. Mack said t only holds 2 cans for day cab and 2.5 cans on sleepers. Did I get wrong info maybe? I usually charge by high pressure 2 times ambient temperature . Where is the high pressure switch located? I know low pressure is on the dryer. tommrrow I am going to put a garden hose on the condenser while running and see if that changes high pressure. If it does not lower it does that mean the condenser is plugged? thanks for all replies. Quote Link to comment https://www.bigmacktrucks.com/topic/46614-1991-mack-ch613-ac/#findComment-344411 Share on other sites More sharing options...
br549 Posted September 4, 2016 Share Posted September 4, 2016 Does it have an air control fan or a automatic fluid control fan on it? If air control I think that model had a trinary switch [3 pole] that was mounted on the drier and when the pressure got high it would kick the fan in. If it has a fluid automatic it sense the air temperature in front of the fan and kicks in automatic, they used a binary switch [2 pole] on the drier. Day cab should be 3lbs. Either system the switch should cut off when pressure gets to high. Run the truck at a higher RPM if it has a automatic fan and see if that helps any. On the air fan unplug it and see if it stays kicked in all the time and see if pressure goes down. Sounds like every thing has been replaced. I don't know if it would cause it but make sure the drier is installed in the right direction, in & out. Quote Link to comment https://www.bigmacktrucks.com/topic/46614-1991-mack-ch613-ac/#findComment-344538 Share on other sites More sharing options...
usrjcro11 Posted September 4, 2016 Author Share Posted September 4, 2016 It has a fluid control fan. I can here it and feel the air volume changing when idling.. The drier can only go one way because of the law pressure switch sticks out on the side. I will go check out anyway. Good point. Thanks Quote Link to comment https://www.bigmacktrucks.com/topic/46614-1991-mack-ch613-ac/#findComment-344550 Share on other sites More sharing options...
Dirtymilkman Posted September 4, 2016 Share Posted September 4, 2016 Sounds like there is internal restriction somewhere. If it was completely plugged you would be pulling a vacuum on the low side. You could have gotten dirt in the system by accident when installing. Or the expansion valve could be partially blocked. Sometimes flushing will loosen junk up inside but you don't have the pressure to push it out. 250psi will push the gunk around where your shop air at 125psi couldn't. We use to use nitrogen to flush systems. More pressure and no moisture in it. Quote Link to comment https://www.bigmacktrucks.com/topic/46614-1991-mack-ch613-ac/#findComment-344557 Share on other sites More sharing options...
usrjcro11 Posted September 4, 2016 Author Share Posted September 4, 2016 Thanks for reply. When I was flushing I thought I was getting good airflow. Going to take lines off and probably replace the condenser and might replace evaporator also.. Quote Link to comment https://www.bigmacktrucks.com/topic/46614-1991-mack-ch613-ac/#findComment-344613 Share on other sites More sharing options...
usrjcro11 Posted September 5, 2016 Author Share Posted September 5, 2016 The parts guy at Mack said 2 cans or I may have misunderstood . I thought it was 3 cans also. What does everybody agree with. I know br said 3 cans. Quote Link to comment https://www.bigmacktrucks.com/topic/46614-1991-mack-ch613-ac/#findComment-344649 Share on other sites More sharing options...
Dirtymilkman Posted September 5, 2016 Share Posted September 5, 2016 3 cans would be 2 1/4 pounds Quote Link to comment https://www.bigmacktrucks.com/topic/46614-1991-mack-ch613-ac/#findComment-344653 Share on other sites More sharing options...
wilbur Posted October 1, 2016 Share Posted October 1, 2016 Mine says on the radiator 3# which is 4 12oz. cans. 2000 CH 613 Quote Link to comment https://www.bigmacktrucks.com/topic/46614-1991-mack-ch613-ac/#findComment-347490 Share on other sites More sharing options...
tjc transport Posted October 1, 2016 Share Posted October 1, 2016 correct. 3 pounds, or four 12 ounce cans. and the high pressure switch should shut the system down once the high side hits around 350 PSI Quote when you are up to your armpits in alligators, it is hard to remember you only came in to drain the swamp.. Link to comment https://www.bigmacktrucks.com/topic/46614-1991-mack-ch613-ac/#findComment-347497 Share on other sites More sharing options...
usrjcro11 Posted October 5, 2016 Author Share Posted October 5, 2016 Update on problems. Put a new clutch on fan. Helped little but high side too high. With truck running and AC on used a water hose on the condenser and pressure dropped immediately. Used truck pulling Lowboy and dozer. AC cool. Put gauges on it about two days later and high side high again. Replaced condenser and AC has been cool since. Thanks for all replies Sent from my iPad using Tapatalk Quote Link to comment https://www.bigmacktrucks.com/topic/46614-1991-mack-ch613-ac/#findComment-347880 Share on other sites More sharing options...
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