I have a 1998 v6 3.8l and I’ve been ac certified for a few years and I have never had something I couldn’t figure out one way or another but on this thing I’m completely stumped. So my ac just stopped working one day after I parked it so the next day at my shop I checked the compressor and the clutch is not engaged pretty much what I expected so I went to hook up the ac machine to see if I was low on Freon and it all spewed out the low side port when I took the cap off so I figured that was my leak and the compressor isn’t kicking on because it’s low so I get a new service port and go recharge the system and it fails the leak test I find the condenser is leaking so I replaced the condenser and the accumulator and recharge it compressor still doesn’t kick on so I check the fuse and it’s ok so I check the ccrm and found the clutch relay was bad so I replaced the ccrm with a used one out of a 2000 (should be interchangeable) and the compressor kicks on for a second and the clutch is making a lot of noise so I replace the compressor and liquid line (with orifice tube) and flush the evaporator to have a virtually new ac system and I won’t have to worry about it since this is gonna be my daily for as long as it lasts so I charge the system after repairs and the compressor kicks on for a sec then kicks back off and won’t kick back on unless switch is cycled. Slapped 2 new pressure sensors high and low just in case it was one of those still same results. After doing some readings on all data the pcm kicks the compressor off if it causes the rpm to drop more then 200 rpm which I noticed the rpm were dropping when the compressor engages but after reading data and turning the ac on for the second it’s on it causes the rpm to drop 400 rpm had the compressor warrantied out new one does the same thing sometimes it stays on longer then others and the lines are getting cold if it stays on long enough as far as I can tell the ac system is ok but it causes the rpm to drop drastically so it keeps the compressor off. I cleaned throttle body and iac hoping that would do something but I’m stumped any suggestions would be greatly appreciated.

 

Hello,

Interesting Situation.

I Could Not Pullup a 98 So I Am Posting 2000 Mustang Shop Manual Info. One On A/C Clutch Relay Control and The Other on IAC Control. It's Just What Seemed Like it Might Help. If You Need Some Other Shop Manual Info LMK and I Will Try and Find For You! I'm in Ca. Too, Gotta Have Air. Have you Tried Hot Wiring Compressor To Test A/C Operation and See How it Behaves???

Just an FYI, As Per Rock Auto Your CCRM Interchanges from 1994-2000. Most of Those Have a Core When Purchased New But The Four Seasons Do Not! Just in Case Your Used One Causes Issues. Most Good Parts Houses Also carry Four Seasons as an A/C Tech You Likely Knew That!

https://www.rockauto.com/en/moreinfo...Sa4%2FSvMwFTBE

Mgb,

Kc

 

When I manually cycle the ac on and off to keep the compressor engaged the high side goes up to 200 psi and low side drops to about 40psi and the air will start to blow cold but unfortunately I can access the links you posted I cleaned out the IAC might try just slapping a new one but I’m really confused on why the ac is causing such a harsh rpm drop