Poor AC at idle - have pressures/duct temps

Friendly format provided to inquire about automotive a/c systems.
Archived Forum

Moderators: bohica2xo, JohnHere, Tim

Post Reply
Gear Head
Posts: 1
Read the full article
Joined: Mon May 29, 2023 12:22 pm

Poor AC at idle - have pressures/duct temps

Post by Gear Head »

hey all,

long time lurker, first post on the forum.
I'm having issues with my 07 F-150 and it's A/C performance. it's a CCoT system. I did an engine overhaul and replaced the compressor with ford OEM, new condenser, suction line, orifice tube and pressure/return lines along with a new accumulator. I replaced the evaporator in the dash about 8 months ago. Holds vacuum at 29.5-30inHG overnight so pretty damn leak tight.

i have a manifold set, at 65 deg ambient, engine idle 675rpm i get this:
Low Side: 30psi
High Side: 225-250psi
Duct temp: 50 deg F

the temps eventually get cold after driving for about 15-20 mins but creep up again if coming back to stop/go traffic.
i think that the high side is too high and the low side isn't low enough which is why i get poor duct temps.

What do i look at first?
Preferred Member
Posts: 1181
Joined: Sat May 02, 2020 1:48 pm
Location: Texas

Re: Poor AC at idle - have pressures/duct temps

Post by tbirdtbird »

1. valid test of system not possible below 80F ambient
2. pressure readings s/b at 1500 rpm/max fan/max cold/doors open / recirculate (ie full load test). Then report back the numbers.
3. your low is actually about right. The high we would like to see lower. Condenser fan working properly?
4. *No* car AC will perform well at idle, the compressor is not able to do much work at idle speed. That is why we spec 1500 RPM
When considering your next auto A/C purchase, please consider the site that supports you: www.ACKits.com
User avatar
Site Admin
Posts: 1052
Joined: Tue Apr 12, 2016 2:19 pm
Location: Scottsdale, Arizona

Re: Poor AC at idle - have pressures/duct temps

Post by Tim »

Make sure the fan clutch is working correctly. Mist the condenser and see if temps drop. Having the correct refrigerant charge in the system is a must.
Please support ACKITS.com for your Auto A/C Parts and Tool needs.

Help Support the Forum
Post Reply