Is it a bad pressure switch?
Thread Starter
|
Cross-Country
Joined: Jul 2017
Posts: 66
Likes: 1
Is it a bad pressure switch?
94' F150, 302, auto, 132K.
AC compressor clutch does not engage when AC is switched on from inside truck.
I pulled electric supply wire plug off of the AC pressure switch & short circuited the plug with a piece of wire. Compressor clutch engaged & spun.
I do not have an AC pressure gauge.
So it seems either the system pressure is too low to activate the pressure switch or I have a bad pressure switch.
How can I test the pressure switch in order to isolate my problem?
AC compressor clutch does not engage when AC is switched on from inside truck.
I pulled electric supply wire plug off of the AC pressure switch & short circuited the plug with a piece of wire. Compressor clutch engaged & spun.
I do not have an AC pressure gauge.
So it seems either the system pressure is too low to activate the pressure switch or I have a bad pressure switch.
How can I test the pressure switch in order to isolate my problem?
Logistics Pro
Joined: Dec 2003
Posts: 3,777
Likes: 863
From: Foothills of NC
Even a cheap charging kit will have a gauge with it that will give static pressure and tell you if there is a charge in the system. You can look up static pressures by temperature online and see what the low side should be for the temperature outside.
Fleet Owner
Joined: Apr 2008
Posts: 24,318
Likes: 5,128
From: 0,0,1
If you want to check it on the cheap, get one of those recharge can that has the gauge on it. Then you can test the pressure and add if needed at the same time without having to dish out $100+ for a halfway decent set of gauges.
Thread Starter
|
Cross-Country
Joined: Jul 2017
Posts: 66
Likes: 1
OK. I bought a can of R-134 Freon with a gauge. Started the truck & let it warm up. Turned the AC & fan to max. Attached the R134 & got a reading of only 15 PSI. Added R134 until I got a reading of about 40 PSI. The compressor began to cycle on/off. About 1 second on & 3.5 seconds off. Added enough Freon to get to about 45 PSI & removed the can. The compressor continued to cycle on/off.
But..............................
Still no cooling. AC blows as warm as pre Freon charge.
But I now know the pressure switch is OK. Do I have a bad compressor? What else could it be?
But..............................
Still no cooling. AC blows as warm as pre Freon charge.
But I now know the pressure switch is OK. Do I have a bad compressor? What else could it be?
Hotshot
Joined: Jan 2004
Posts: 19,762
Likes: 1,079
From: St Louis
You probably need more refrigerant. If you only had 15 psi to start with, it was essentially empty. There should be a sticker under the hood that gives the total charge. You can guess at it and hope you get lucky or you can fix the leak and then charge it accurately by weight.
Logistics Pro
Joined: Dec 2003
Posts: 3,777
Likes: 863
From: Foothills of NC
If the compressor is off more than on, it's still under charged. Add another can, or at least half of one.
Trending Topics
Thread Starter
|
Cross-Country
Joined: Jul 2017
Posts: 66
Likes: 1
I added more r134. no change in symptoms.
Per the gauge on the can, it reads about 25-30psi when the compressor cycles on & about 45psi when the compressor cycles off.
Per the gauge on the can, it reads about 25-30psi when the compressor cycles on & about 45psi when the compressor cycles off.
FTE Stories
Ford Trucks for Ford Truck Enthusiasts
Top 10 Most Expensive Ford Trucks Ever Sold on Bring a Trailer
Joe Kucinski
2027 Ford Super Duty Buyer's Guide (Every Model, Engine, & Package)
Brett Foote
Top 10 Ford Truck Tragedies
Joe Kucinski
AEV FXL Super Duty - the Super Duty Raptor Ford Doesn't Make
Brett Foote
Lobo Vs Lobo: Proof the F-150 Lobo Should Be Even Lower!
Michael S. Palmer
Ford's 2001 Explorer Sportsman Concept Looks For a New Home
Verdad Gallardo
10 Best Ford Truck Engines We Miss the Most!
Joe Kucinski
2026 Shelby F-150 Off-Road: Better Than a Raptor R?
Brett Foote
2027 Super Duty Carhartt Package First Look: 12 Things You NEED to Know!
Michael S. Palmer
Hotshot
Joined: Jan 2004
Posts: 19,762
Likes: 1,079
From: St Louis
The pressures appear normal on the surface but lack context. Those are the typical -pressures for when the low pressure switch cycles but, we don't know either the ambient, the load or the cycling rate.
Did you check the temperature of the evaporator inlet and outlet tubes while the system was cycling?
Fleet Owner
Joined: Apr 2008
Posts: 24,318
Likes: 5,128
From: 0,0,1
Still needs more refrigerant. A front only system takes almost 3 cans, more if you also have rear air.
Thread
Thread Starter
Forum
Replies
Last Post
BigSix1
1987 - 1996 F150 & Larger F-Series Trucks
4
Jun 1, 2011 08:22 PM