I got my truck back form the shop, they replace two lower ball joints, passenger upper and put new brake pads on the front. Now my air starts switching to defrost when i approch 50-60 mph but it will come back on when i am coasting and go off again under acceleration. It might not work under heavy acceleration at speeds lower than that but i just havnt felt the need to try it out. So im guessing there is a small vacume leak somewhere causing the air to switch the defrost but why would it only be at that speed and under acceleration? has anybody else had this problem?

 

Its a vacuum leak. The plastic ball that you see on your fender wells is a vacuum reservoir. It holds vacuum pressure so that your a/c system can use vacuum when vacuum isn't pressent in the engine (like when cruising or under acceleration). Is this during Max A/c?

Here is a few things to look for:

1. THe check valve in the ball or loose connections from the intake to the ball, and from the ball to the firewall.

2. Loose firewall connector on the inside bottom of your passenger side. Drop your glove box and look for a connector with two vacuum lines at the right. Connector should be white. ONe line is supply for the system and another is vacuum for the heater control valve.

3. Check your heater control valve. Make sure its vacuum line doesn't have cracks or is broken. Also make sure that the diaphram in the HCV is still good and can hold vacuum.


When on max a/c vacuum is applied to the HEater control valve, dash vents (which default to defrost when no vacuum), and re circulation door. Any leak in any part of these will cause your problem.

 

no he is wrong. your ac is turning off under wot because it is taking power away from the engine.

 

I would believe that except that it has never done that before now and im not sure if the air is still on when it switches or if it is off. it just switches to blowing out on defrost.

 

You are talking about the WOT relay which cuts power to the compressor.....sorry but you are wrong because that has nothing to do with which vent the air comes out. This is a vacuum problem.

 

So the WOT relay cuts out power to the compressor so it that why in low range the air gets hot?

 

The WOT relay is activated by the PCM under certain conditions. It looks at your pressure and cycling switches and your throttle position sensor. When you have 100% throttle the PCM will use this relay to turn off your compressor so that you can use all the available power possible.

 

ok thanks for explaining that. but if anybody else has some idea whats going on please share.

 

I agree with sheltonfilms. Check all those connections from the ball.

 

I'll bet they either cracked the reservoir ball or knocked a vacuum line loose while doing the suspension work. The reservoir vacuum is shared between the A/C and the Pulse Vacuum Hublock system for the 4WD, so check the PVH solenoid to be sure that the vacuum lines are in place there and also at the hubs.

 

Yeah when they messed with that passenger upper control arm/ball joint that would be when it was messed up. If it was me I would take it back to the shop and have them find the problem/ fix it.

Or take a look at the last page of this link:
http://rockledge.home.comcast.net/~r...iagnostics.pdf

 

I instaled the Rugged ridge hubs so i dont need the vacume to run them anymore thank god. but ill check everything out when i get time and see what i can find.

Thanks for the link! I would take it back except im 150 miles away so i cant right now.

 

I have loooked around the vacume lines and havnt noticed any that would be leaking but my truck has been throwing P0171 codes and it comes back even after i get it cleared. Ive read on here that it could mean there is a vacume leak but also it could be other things as well. So i guess i should really be looking for a leak or take it to a shop to look at it.

 

I wouldn't take it to a shop just because you can pretty much fix it for free instead of paying around 75 bucks just for them to look at it.

 

If you are in 4lo and the ac blows hot your fan clutch is on the way out.

IMHO, electric fan is the best upgrade for colder ac at a stop.

 

I was looking around on the truck last time i was home still trying to find the leak. I found a rubber hose that connects the round thing on the passenger side (might be the heater core? not really sure) well it wasnt snapped into place all the way so i put it back on it was supposed to be, havnt drove it since then so im not sure if its fixed or not. I couldnt find the ball that everyone was mentioning so im not really sure where that is.

 

I finally had this looked at since i could never find where it was leaking. The guy that worked on it checked just about everything and replaced most of the lines and finally found the one place that was leaking. the hub actuator motor or something like that was letting vacume leak by. so he just capped it off since i have manual hubs now and put a check valve in.

 

So where is the WOT relay? I want to bypass/switch so it won't cut out. Seem the slightest hill in 4th or 5th and I loose cold. I don't care about MPG or power loss.

 

It's been 6 years and nobody knows where the WOT relay is hiding? BTW it also affects the heater blower. Does Ford think the heater blower robs engine power too?

 

I have never seen a WOT situation affect the blower unless the vacuum dips and throws the door in the wrong position sending the air somewhere else.

I have a 2000 sitting at work and will look tomorrow night, but you should be able to take the top off your PDC where the rest of the relays are and look under the cover, it will probably be well marked. There are explanations under the cover of what relay and what fuse does what. I can confirm that tomorrow evening unless someone will chime in with a snapshot.

 

WOT relay is in the engine fuse box

 

Which is synonymous with PDC (power distribution center) LOL.

I worked in a mold shop for a while that was working on a fuse box, the term PDC is what they used and it kinda stuck in my head. Like I said unless someone else does I'll post a photo with a circle and an arrow tomorrow evening.

 

Ford calls the engine fuse box the BJB
Battery Junction Box lol

 

Eagerly awaiting and greatly appreciated.

 

OOPS I am so sorry I completely spaced it. I have an electrical wiring diagram too now but its at work and I'm headed up north tomorrow morning to pick up my donor vehicle for my ranger v8 swap.

Can someone else post up a pic right quick of the relay location because I'm an idiot? I'll owe you one.