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Canadafix, Canadian class A certified
Category: Ford
Satisfied Customers: 1632
Experience:  Canadian automotive technician.Class "A" certified
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Ford Explorer Limited: I have a 1999 Ford Explorer Limited

Resolved Question:

I have a 1999 Ford Explorer Limited Edition V6 SOHC and I recently had the chain guides inside the engine replaced. I know they took the engine out and put it back in but since then, my air conditioning is acting weird. when I'm driving around town, at low speed, everything is all right but when I get on the highway at high speed, as soon as I reach the fourth and fifth speed, the air conditioning either stops working for a second or two, or suddenly stops blowing from the front and blows up in the windshield then back to the front. And, the air that blows is really low. I can have the fan speed set at high, it doesn't matter.
If I release the accelerator, the fan speed comes back to normal!
So, if I go on a long trip on the highway, after a short time the system would freeze because the cold air is just not coming out.
I have to release the accelerator every now and then to prevent the system from freezing and it costs me a lot on gas because of that (and I have to use the a/c as I live in the Caribbean. It's very hot here ... lol).

So, a friend of mine told me it could be a vacuum hose (I don't know if it's the proper word...). Today I went to an air conditioning repair shop and they checked all the vacuum hoses and a little ball-like plastic tank in the front bumper that's connected to one of those hoses. The hose was punctured so they fixed it and the guy told me everything else is OK so it had to be that.

I left the place, everything was fine but when I got on the highway, SAME THING !!!!

So, I'm desperate, I really need my air conditioning the way it was before!!!!

Could it be electrical? Or do you think they haven't checked properly?

What should I do next???

I have a feeling it's a little thing but nobody seems to be able to find it...
Oh and, before I forget, it is a digital controlled a/c. Just in case it matters...
Submitted: 4 years ago.
Category: Ford
Expert:  Canadafix replied 4 years ago.
Welcome back to Just Answer.

Your friend is correct with the vacuum problem.
The doors for the AC/heater system are operated by vacuum.
This vacuum comes from the engine, is stored in that ball you spoke of and directed to the heater control.

Engine vacuum is highest when the throttle is closed and drops off the more the throttle is opened. If there is a small leak in the system, this is why it works at closed throttle.

The mechanics at the AC shop missed something. Perhaps a check valve between the reservoir and the engine block or a cracked hose.
If the check valve is not in place, the vacuum leaks off back into the engine.
The reservoir is to maintain a constant vacuum source.

I agree with you that it is a little thing. The trick is to locate it.
Here is the vacuum diagram for your Explorer's system.


Your questions and comments are welcome to me.
Thank you.
Customer: replied 4 years ago.
Ok. thanks! I'll go back tomorrow and have them check again.
And, just in case, if this check valve is missing, where should it be on that diagram?

I'll have to show them that because here, in the Dominican Republic, they're like 50 years behind. They don't really use or know how to use diagrams. they're more like street mechanics !!!
Expert:  Canadafix replied 4 years ago.
Thank you for the reply.

The check valve would be at the bottom supply hose that goes to the engine.
The arrow that points to 13.
It would allow vacuum to the reservoir, but not back out.

Let me know if you need further assistance.
Thank you,
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