When driving at highway speed, the A/C stops working?

GREASE-MONKEY-BEAR

MEMBER
2004 FORD FREESTAR
3.9L
6 CYL
2WD
AUTOMATIC
1,703,862 MILES

Okay, not sure. When the van is parked it has great air conditioning but when you get up to highway speed, it stops working. Replace the thermostat blower motor the Blower Motor Resistor did a flush. Then there is the heating problem, I have no heat at all. The next step is hooking up a set of gauges to get an a/c reading. Any help would be greatly appreciated. Thank you

Wednesday, September 28th, 2022 AT 4:05 PM

2 Replies

KEN L

MASTER CERTIFIED MECHANIC
51,530 POSTS

This sounds like either the engine is overheating and cutting the A/C off or you have an A/C compressor that is starting to go out. First, when the engine is cold remove the radiator cap and check the coolant level. If low please fill it up, this may fix the heater as well. Next you will need a gauge set to check the pressure when the engine is revved up to about 2,500 RPMs.

This guide can help you see what's going on:

https://www.2carpros.com/articles/re-charge-an-air-conditioner-system

and

https://www.2carpros.com/articles/car-air-conditioner-not-working-or-is-weak

Please go over these guides and report back.

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Thursday, September 29th, 2022 AT 10:52 AM

GREASE-MONKEY-BEAR

MEMBER
3 POSTS

Thank you, great information. Just the overheated by the dashboard gauge it says it not overheating, I know that the gauge could be wrong, so I put my scan tool on it to read what the pc is reading and no show of overheating...
My game plan is to hook up my gauges to the van plus use a can of foaming a/c condenser coil cleaner, with a pressure washer.

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Wednesday, October 5th, 2022 AT 12:43 PM