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A/C seems to be always on?

Tiny
BIG DOUBLE
  • MEMBER
  • 2009 FORD RANGER
  • 2.3L
  • 4 CYL
  • 2WD
  • MANUAL
  • 90,000 MILES
I noticed my gas mileage is down 40 miles per tank full, When I turn on just the vent (inside) cold air comes out especially when it was hot outside, instead of warm air. I notice the truck just has a very short noticeable hesitation when turning on the fan. I assume it is the A/C kicking on. Also, when I turn the fan on at night there is a quick dim of the headlights, like something is drawing the power. My mechanic said the wiring diagram says it should be running all the time.
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Thursday, October 13th, 2022 AT 9:19 AM

12 Replies

Tiny
JACOBANDNICKOLAS
  • MECHANIC
  • 108,205 POSTS
Hi,

The compressor should not be engaged at all times. When the AC is requested, the compressor should cycle on and off. When the defroster is on, the same thing will happen. When you only request the vent (fresh air) it shouldn't be on.

As far as the lighting dimming when you turn the blower motor on, it isn't uncommon simply because you have added a larger load to the system. However, I don't know to what extreme you are experiencing.

Here is what I need to know. If you start the truck, turn on the blower motor and have vent only selected, does the compressor engage?

Let me know.

Joe
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Thursday, October 13th, 2022 AT 8:01 PM
Tiny
BIG DOUBLE
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  • 7 POSTS
Yes, the compressor engages after starting the truck.
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Friday, October 14th, 2022 AT 7:18 AM
Tiny
JACOBANDNICKOLAS
  • MECHANIC
  • 108,205 POSTS
The relay may have shorted. Pull the AC relay and switch it with one having the same part number to see if it changes things.

If there isn't one, here is a link that explains how to test one:

https://www.2carpros.com/articles/how-to-check-an-electrical-relay-and-wiring-control-circuit

Let me know what you find.

Joe.

See pic below for the compressor relay location.
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Friday, October 14th, 2022 AT 10:31 PM
Tiny
BIG DOUBLE
  • MEMBER
  • 7 POSTS
I went to the Ford dealer got a new A/C relay and there is no change.
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Monday, October 17th, 2022 AT 7:55 AM
Tiny
JACOBANDNICKOLAS
  • MECHANIC
  • 108,205 POSTS
Does the compressor engage with the relay removed? If it does, there has to be a short to power. If it doesn't, we need to check the terminals where the relay connects. Something is allowing power to make it to the compressor at all times.

Joe
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Monday, October 17th, 2022 AT 5:37 PM
Tiny
BIG DOUBLE
  • MEMBER
  • 7 POSTS
I had my son watch the compressor it engaged most of the time when I turned the fan on a few times. Did not engage when the relay was taken out.

Q: What is the difference between outlaws and in laws?
Outlaws are Wanted.
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Tuesday, October 18th, 2022 AT 5:33 AM
Tiny
JACOBANDNICKOLAS
  • MECHANIC
  • 108,205 POSTS
Hi,

Good one. LOL

If the compressor continues to get power, we may have a PCM providing a ground path to actuate the compressor clutch or a short to ground.

I attached the wiring schematics below for the AC circuit, so you have a reference.

Here is what I want you to test. Remove the compressor clutch relay. There are 4 pins. The wire in question will be white with a brown tracer. It will be either pin 85 or 86 identified. If you find it has power at all times, check the opposite pin.

The white/brown wire goes to the powertrain control module. The PCM provides a ground path to that wire when the AC is requested. Once the path is provided, an electro-magnet in the relay closes the connection between pins 87 and 30 to send power to the compressor.

So, I need you to check if the white/brown wire has continuity to ground with the key on and AC requested. If it does, turn the AC off and see if it still has ground. This will determine if there is a short to ground or if there could be an issue with the PCM.

Let me know the results.

Take care,

Joe

See pics below.
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Wednesday, October 19th, 2022 AT 5:10 PM
Tiny
BIG DOUBLE
  • MEMBER
  • 7 POSTS
I had my mechanic friend do the checking and could not find anything. The AC does not work in the vent or feet position. We think it might be in (behind) the on off switch itself.

Why are red neck crimes hard to solve?
All the DNA is the same and there are no dental records.
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Thursday, October 27th, 2022 AT 10:46 AM
Tiny
JACOBANDNICKOLAS
  • MECHANIC
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LOL Like the joke.

Does the compressor turn off if you disconnect the switch? It should, and the switch itself does make sense. You could also check for continuity through the switch in both the on and off position to see if the circuit is constantly completed.

Joe
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Thursday, October 27th, 2022 AT 5:18 PM
Tiny
BIG DOUBLE
  • MEMBER
  • 7 POSTS
My mechanic friend put a new switch in and there are no changes with the A/C being on when not needed. Not running in vent or floor. Do I write to Ford to see if this to be normal or not?
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Sunday, December 4th, 2022 AT 5:29 AM
Tiny
JACOBANDNICKOLAS
  • MECHANIC
  • 108,205 POSTS
Hi,

The idea that it continues to run indicates it is getting power. Where it comes from is the question.

Have you tried removing one fuse at a time to see if there is one that turns it off? By the way, thanks for making me laugh. I needed it. LOL

Joe
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Monday, December 5th, 2022 AT 1:06 PM
Tiny
BIG DOUBLE
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Check out this channels video - https://www.youtube.com/watch?v=FBORpcuhXX8
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Monday, December 5th, 2022 AT 8:07 PM

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