2010 Expedition/AC High Side Fluctuation

[Drae]

Is the AC High Side supposed to drop when the high speed fan kicks on? It goes from 170 or so to about 370 then the high speed fan kicks on then goes back down to 170. The low side stays steady at 40 no matter what. The AC is cold the whole time but just checking to make sure this is normal.For background purpose and AC repair history, I just changed my AC compressor again because the aftermarket AC compressor clutch failed. So I decided to go back with an OEM compressor because I'm starting to understand critical parts are not worth it when it comes to saving a few dollars. The original compressor was also an AC clutch failure but I didn't figure out until I replaced it with the aftermarket compressor. I was told by a shop it was the compressor because of the noise it was making. It sounded like a French horn when it engaged but eventually stopped working all together. I replaced the front expansion valve, AC condenser and did a flush when I installed the aftermarket compressor. There was no metal shavings at the time and none now when putting the new Motorcraft compressor on.

 

[Drae]

I just took another look at my issue. I thought one fan was on constantly while the AC was on initially but when I checked again today it wasn't. Both fans will kick on for about 10 to 15 seconds to cool the condenser and radiator. That's when the high side pressure will drop to 170. After the fans go off the pressure will climb back to around 370. It just continuously cycles this way. Maybe I'm looking at a fan issue because I swear a fan is supposed to be on as soon as the AC is on?