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Ron
Ron, ASE Certified Technician
Category: Ford
Satisfied Customers: 33407
Experience:  23 years with Ford specializing in drivability and electrical and AC. Ford certs and ASE Certs
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2001 f250 and i think my ac is acting weird. I know i have a

Customer Question

2001 f250 and i think my ac is acting weird. I know i have a slow leak (ill find that here soon) but when i turn the ac on max cold a/c it starts at defrosters then eventually (sometimes 10 second later) comes out the top vents. Sometimes it will last for 10 mins, sometimes 1 min- it will eventually just blow out the defrosters again. I can turn the system back off then on again and its rinse and repeat. what is wrong here?
Submitted: 2 months ago.
Category: Ford
Expert:  Ron replied 2 months ago.

Hello. My name is ***** ***** I am happy to assist you today. Give me just a moment to review your post, and I'll be right back with the help you need.

Expert:  Ron replied 2 months ago.

Your AC/Heater system is designed to divert to the defrost mode when the system is low or slow to hold vacuum which controls the actuator doors and if you have a vacuum leak it will cause the type of problem you are having. In order to solve this you are going to need to do some testing to trace the vacuum leak down. Are you able to do this if I send you the steps?

Customer: replied 2 months ago.
ah. that would make sense, on occasion after driving the rpms will fluctuate about 150-200 rpms. yes, i should be able to
Expert:  Ron replied 2 months ago.

Okay I have enclosed the complete factory steps in the link below. Download the file and scroll down to pinpoint test A1 and follo the steps. You will need a hand held vacuum pump to check the vacuum motors if it gets that far. Start with taking a close look at the vacuum reservoir located next to the battery as its a common place for the line to leak. Post back if you have more questions and or need more help and we can work from there.

https://dl.dropboxusercontent.com/u/104923897/Pinpoint%20test%20A1.pdf

Customer: replied 2 months ago.
a2 step 2 where are these hoses? maybe i am just missing them? exhaust manifold which side?
Expert:  Ron replied 2 months ago.

They run from the intake manifold over to the vacuum reservoir and from there into the firewall and connect to the AC control panel. The supply line is the black line from the reservoir to the Ac control panel.

Customer: replied 2 months ago.
ok maybe I'm a little confused, are we talking "vacuum reservoir" that is the brake booster?
Expert:  Ron replied 2 months ago.

No, the vacuum storage reservoir for the AC system. It mounts on the battery tray. See it in the link below. Take a look at it and the lines in and out of it first, there known to break due in that area.

https://dl.dropboxusercontent.com/u/104923897/VAc%20reservior%20Sep%207.pdf

Customer: replied 2 months ago.
ok ill check it out. now does the ac system need to be filled with freon first then look for this issue?
Expert:  Ron replied 2 months ago.

No, air flow out the correct vent has nothing to do with the AC cooling. That being said the engine dose need to be running to produce vacuum.

Customer: replied 2 months ago.
ok i checked out this black box (vacuum) and all the lines seem fine, however next to the box (against the frame of the truck to the left of the black box), there is one vacuum hose that curls down into the engine bay, attaches to a bracket near front right wheel next to brake line, then curls down and is attached to nothing. is this the problem? and where does it go?
Expert:  Ron replied 2 months ago.

If the line is coming off the vacuum reservoir then yes it may be a problem. There should be no breaks in the vacuum supply line.

Customer: replied 2 months ago.
any idea where that line should be going? its attached to the brake line bracket next to the passenger front wheel
Expert:  Ron replied 2 months ago.

Are you sure its a vacuum line, with the engine running do you feel any vacuum on the end of it?

Customer: replied 2 months ago.
the line i am holding has an elbow that goes down through engine bay and curls around to where brake line is. if you can see the connector on the bottom right of the picture that line goes back into there, then goes off there into black box.
Expert:  Ron replied 2 months ago.

The red line is the vacuum supply line from the engine and the black line is the feed line to the control panel through the firewall . The black box is the reservoir . Which line are you seeing that is loose?

Customer: replied 2 months ago.
it is the black line that goes down attached on brake hose bracket. about a 1 foot long after bracket
Expert:  Ron replied 2 months ago.

Okay that line should make its way back up to the firewall. You can check it for leaks by removing it from the reservoir and applying vacuum to it, it should hold vacuum if there are no leaks from it the the AC control panel.

Customer: replied 2 months ago.
there is no leak until the hose that is unattached. where is this connected to the firewall? i really can't find this broken hose anywhere
Expert:  Ron replied 2 months ago.

It should go into the firewall right next to the AC/heater plenum. Unfortunately I do not have an exact picture.

Customer: replied 2 months ago.
alright so after nearly pulling out my hair last night (haha) looking for a hose and or leak. i turned the truck back on with ac on and realized that i am leading us both down a rabbit hole. the rpms ONLY jump when the compressor is cycling on and off, which it does about every 1/5 seconds. so, there is no leak. lol. the rpms are clearly only moving when the added load of the compressor is turning on. So, i guess we are back to square one.
Expert:  Ron replied 2 months ago.

The compressor will cycle if the system is low of Freon. A vacuum leak in the system will cause the AC vent air to divert to defrost, is that now not happening?

Customer: replied 2 months ago.
hmmmm. ok. well i guess its two fold. i still haven't found this vacuum leak in the system. but it seems it only goes to defrost when freon is low, does that sound right or no?
Expert:  Ron replied 2 months ago.

The Freon level will not affect the air flow, only cooling.