Tricky Air Conditioner

Disclaimer: Links on this page pointing to Amazon, eBay and other sites may include affiliate code. If you click them and make a purchase, we may earn a small commission.

kingpolaris

Member
Joined
Aug 13, 2015
Posts
12
Reaction score
1
Location
Ridgecrest
Ok, I'm don't consider myself an a/c newb but this rig is kicking my ass.

2003 Expedition Eddie Bauer

A/C kicks on as soon as i start the vehicle but only stays on for about 5 seconds. Refrigerant pressures are low (i tried jumping out the low pressure switch) but shouldn't the compressor cycle back on after the pressure comes up - like ever other car i have ever worked on. I've checked high and low side pressure switches, interior and exterior air temp sensors, clutch relay and diode and all are good. The only way i can get the a/c to stay on is to jump out the compressor relay located behind the lh headlight. the only thing i can think of is it might have a bad WOT switch (wherever that is), a bad coolant temperature switch (again, wherever that is) or the dreaded bad pcm?

I'm running out of things to check so any advise would be awesome.

Thanks!
 

Hamfisted

Full Access Members
Joined
Nov 20, 2012
Posts
2,582
Reaction score
1,467
Location
Ft Lauderdale
Are you trolling us ?
Why wouldn't you just add some freon to the system rather than "jump" system safety switches ? The issue is "kicking your ass" ? Take it to a shop. Don't ruin it.
 
OP
OP
K

kingpolaris

Member
Joined
Aug 13, 2015
Posts
12
Reaction score
1
Location
Ridgecrest
Are you trolling us ?
Why wouldn't you just add some freon to the system rather than "jump" system safety switches ? The issue is "kicking your ass" ? Take it to a shop. Don't ruin it.


i jumped the switch because it is a ***** to get a meter on the low pressure switch. suction pressure switch is fine, freon is fine.
 

Skauber

Full Access Members
Joined
May 31, 2014
Posts
366
Reaction score
29
Location
Cagayan de Oro, Philippines
If you jump the low pressure switch, and it turns on, logic says that the pressure is low and the switch opens to protect the compressor from running dry, right? You need to connect an AC manometer on it to check the pressures, if it's low then you probably have a small leak somewhere. Just adding some freon is not gonna permanently fix your problem and may even be illegal to do without verifying that you don't have a leak, depending on where you are located. Anyway, check your pressures, if you don't have the tools to do that then it's time to contact a AC specialist.


Edit: it's a bit unclear from the opening post, but you say "Refrigerant pressures are low (i tried jumping out the low pressure switch)", and then "The only way i can get the a/c to stay on is to jump out the compressor relay". Have you checked the pressure in the system with a manometer? And does this mean that if you jump the low pressure switch, it does NOT turn on, but only when you jump the relay?
 
Last edited:

Skauber

Full Access Members
Joined
May 31, 2014
Posts
366
Reaction score
29
Location
Cagayan de Oro, Philippines
BTW, the few seconds the compressor runs when starting the engine is by design. It does that regardless of the settings on the AC-system. When starting the engine, the AC compressor will engage for a few seconds to circulate the system, it is a preventive measure to ensure that the oil doesn't accumulate in the compressor and cause leaks, a problem commonly seen in vehicles after winter when the AC hasn't been used for more than 6 months.
 

stamp11127

Full Access Members
Joined
Mar 10, 2012
Posts
6,218
Reaction score
1,250
Location
Temple, Georgia
Any advice.....go buy a good set of gauges and diagnose the correct way. Winging it is a waste of time.
 
OP
OP
K

kingpolaris

Member
Joined
Aug 13, 2015
Posts
12
Reaction score
1
Location
Ridgecrest
I've got a good set of gauges, a vacuum pump, a weight scale, a full bottle of 134a (30lb), and about every other tool needed to fix this problem - i hope.

I just got this rig and this is my first no cool experience with an expedition but I'm not totally unexperienced when it comes to ac (i have a bs in hvac engineering - not that that matters in this situation).

i guess i needed a little more of a back story on this. i received this ford from my uncle...for free. It had a blown spark plug, no ac, and a few other problems. i finished the spark plug repair last week (super fun) and now it runs ok. I'm still chasing problems, e.g. code P0356 (F ignition coil), so i decided to tackle the no ac problem while i wait for parts. i hooked up my gauges and noticed that my pressures where over 100 psig on both high and low sides which seemed normal. i noticed that someone put leak detection dye into the system so i recovered the freon and pulled a vacuum. system held a vacuum for about an hour with no movement in the gauges - sweet no leaks. i began to weigh fresh freon back into the unit (58 oz is factory charge) and got about 10 oz into the system before all pressures equalled out and system would accept no more freon. like every other vehicle system that i have ever worked on in the past i started the vehicle and tried to fill the system through the suction side while the compressor cycles. i could only charge the system for about 5 seconds before the system would kick out on something and never come back on (not sure at this point but i and everyone here would assume low pressure). systematically jumped out the low pressure switch, high pressure switch (multimeter indicates that that one is good), pulled and verified that the interior and exterior temp seniors were ok with an ohm meter. i replaced the relay (and diode) thinking that it might have a weak coil unable to handle the electrical current but no change. the only way i can get the ac to stay on is to jump out this relay. i had to take a break (before i raged) and a look for answers online hoping someone out there has experienced my pain. at this point i think it might be the WOT but I'm not sure how to check it. any useful advise would be awesome.

here is what i found on ALLDATdiy

"The A/C compressor clutch will only be engaged by the PCM if all of the following conditions are met:
The climate control assembly is set to a mode which provides an A/C request to the PCM.
The A/C thermostatic switch is reading a temperature above 37°F .
The high pressure cutoff switch is not open due to excessive pressure in the high side of the refrigerant system.
The low charge protection switch is not open due to insufficient low side refrigerant system pressure.
The A/C compressor relay is switched to the closed position by the PCM.
The engine coolant temperature is not excessively high.
The PCM has not detected a wide open throttle (WOT) condition."

i will not take this vehicle to a mechanic so stop advising that...please.

Thanks again!
 

Skauber

Full Access Members
Joined
May 31, 2014
Posts
366
Reaction score
29
Location
Cagayan de Oro, Philippines
Ok, thanks. That does clear things up a bit more, and it's easier to advice when we know a little more about the background and of course your own abilities and qualifications. I have similar qualifications myself when it comes to HVAC systems.

That said, there are no WOT switch, this is determined by the PCM based on the TPS. What may be the cause for compressor not engaging is if the PCM thinks it's too cold outside, does the outside air temp display work? That sensor is located in front of the condenser, behind the front grille. What type of AC unit do you have? The digital climate control with dual zones, or the standard manual control with manual fan and temp selector?


EDIT: On a side note, do you have any sort of diagnostic OBD scanner? Like the OBDLink MX? If you do, you can download FORScan for Windows, which gives you almost the same access to read data PID's as the dealer has with their scantool.
 
Last edited:
Top