AC issue

[tjrtmaster]

The AC on my Explorer had been running great all summer. I checked it a few weeks ago with a gauge that is used to add more refrigerant and it was well into the green. Yesterday I got no cool air at all even when on Max AC. The compressor cycles on and off constantly every few seconds. To find the problem should I add dye and look for leaks or get a loaner gauge set from Auto-Zone and check the high and low pressures?
Any troubleshooting techniques would be appreciated.
What psi should the high and low read?

 

[koda2000]

How many seconds between when the A/C compressor clutch is cycling on/off? If it's around 7 seconds that's normal. Your lack of cooling may be being caused by a broken blend door or blend door actuator. This was the issue with my '00 Mountaineer this past spring.

 

[Mesozoic]

Ditto. Heater blend door actuator, located behind the glovebox. Easy to get to from inside the truck as long as you drop the glovebox down.

 

[koda2000]

Ditto. Heater blend door actuator, located behind the glovebox. Easy to get to from inside the truck as long as you drop the glovebox down.

Yeah, it's easy to get to the actuator, but getting the rear screw out and back in... not so easy unless you have tiny hands.

 

[Mesozoic]

I believe you just need small 8mm tools, like a 1/4" ratchet with a 12-point 8mm shorty socket, a stubby 8mm box end wrench with a 12-point end, etc. I don't have small hands and it didn't take me much more than about 20 minutes to replace it. The rear screw location is not fun, though.

 

[MAS Tequila]

Mine doesn't have the rear screw anymore.

2 1/2 years and it's still doing fine.

MT

 

[tjrtmaster]

New symptom....I tried it again and the compressor never kicks on at all now.

 

[koda2000]

New symptom....I tried it again and the compressor never kicks on at all now.

Then it might be your refrigerant is low or it might be you have a bad HI or LO pressure switch. Try swapping the A/C relay first.

You may find some useful information in the below thread...
http://www.explorerforum.com/forums...gages-and-disengages-after-recharging.425612/

 

[tjrtmaster]

Then it might be your refrigerant is low or it might be you have a bad HI or LO pressure switch. Try swapping the A/C relay first.

You may find some useful information in the below thread...
http://www.explorerforum.com/forums...gages-and-disengages-after-recharging.425612/

Where is the a/c relay? The low pressure side shows a steady 40 psi.

 

[koda2000]

Where is the a/c relay? The low pressure side shows a steady 40 psi.

The A/C relay is located in the power distribution box in the engine compartment in front of the brake master cylinder. Refer to your owner's manual for the location of the A/C relay. You can swap it with any similar relay located in the power distribution box.

 

[tjrtmaster]

The A/C relay is located in the power distribution box in the engine compartment in front of the brake master cylinder. Refer to your owner's manual for the location of the A/C relay. You can swap it with any similar relay located in the power distribution box.

I swapped the relay with no improvement. I measured the voltage on the low pressure switch and one wire had 14 volts. the other had .2 volts. With the pressure switch connector disconnected I jumped the connector and when I started the Explorer the compressor clutch engaged. I replaced the switch, feeling certain that I had the problem solved but it did not help, still no compressor clutch engagement. Then I checked the pressure from the low pressure side and I have no pressure. Would I loose all of the refrigerant by swapping the switch. Yesterday when I checked it I had about 40 PSI. I am going from bad to worse.

 

[koda2000]

I don't know why you went ahead and replaced the pressure switch. When you removed the pressure switch did you hear the refrigerant escaping? You should have. It's like removing the valve from a tire. The air is going to escape.

At this point you've probably let all (or most) of the refrigerant out and you need to recharge it before continuing your diagnostics. You may have a leak. IDK.

 

[RandomNerd2000]

Get the gauges, HFT has a cheap set I've used for several years, they work fine. Sounds like you have no charge. It sounds to me like it was gassed, and your actuator was screwing up, and you've gotten confused. Get the gauges, hook them up, both the high and low sides, and read what it says.

 

[tjrtmaster]

Get the gauges, HFT has a cheap set I've used for several years, they work fine. Sounds like you have no charge. It sounds to me like it was gassed, and your actuator was screwing up, and you've gotten confused. Get the gauges, hook them up, both the high and low sides, and read what it says.

I got a Loan a Tool set of gauges from Auto Zone and as suspected, I have zero PSI on the high and low side. I also got a Loan a Tool vacuum pump and ran it for an hour down to -30 PSI. I disconnected the pump and I am going to keep the gauges connected for a day to see if the system holds the vacuum. If the vacuum does hold should I add refrigerant and see what happens from there. Will the AC system pull in the refrigerant even if the compressor clutch does not engage?

 

[koda2000]

Having drawn and held a vacuum will help suck in some refrigerant. The pressure in the can will also push in the refrigerant until the pressure in the system equalizes the with the can. With the engine running and the A/C ON the compressor will begin kicking in as the pressure rises.

You still haven't explained where the original refrigerant went. Could it be the valve is leaking? Do you have the plastic valve cover caps? Are their gaskets in place and were they screwed on tightly? Valves tend to leak a little w/out the caps on them.

 

[RandomNerd2000]

If it holds vacuum, add refrigerant on the low side (blue) of the gauges, when it gets to a certain PSI, it'll kick in the compressor and since that's the low PSI side, it'll draw the gas in. Under the hood, there's a sticker that shows how much to add, compare that to the size cans you're using and gas it using the correct amount, you'll probably have some leftover in the can unless you end up with the perfect size cans, in which case, I have a valve that goes on top of the cans I use that hooks to the gauges, I close the valve off (on the can) and allow the system to draw in the remaining freon inside the hose, then disconnect. Be careful on the high PSI side, it is under pressure and there will be freon inside the hose.

If it doesn't hold vacuum, you have to find the leak, or a new charge of gas will leak out. In the 99 I had, it was the valve cores leaking where you gas it, they can be a bear to change. I have the proper tool to change them, it can be had at a parts store, the high side one is a larger core than the small one to prevent improper use of the gauges, everything else is coils, or fittings that bolt on with special seals on them. It's really quite simple once you get how everything works

 

[Jon94]

I don't know why you went ahead and replaced the pressure switch. When you removed the pressure switch did you hear the refrigerant escaping? You should have. It's like removing the valve from a tire. The air is going to escape.

At this point you've probably let all (or most) of the refrigerant out and you need to recharge it before continuing your diagnostics. You may have a leak. IDK.

The low pressure and high pressure switches have Schrader valves underneath them. Unscrewing them does not let any refrigerant out at all.

 

[tjrtmaster]

The low pressure and high pressure switches have Schrader valves underneath them. Unscrewing them does not let any refrigerant out at all.

I agree, I looked at that as well.
Yesterday I put a vacuum on the system and it held at -30 PSI for a few hours. I noticed this morning that the pressure gauge was down from -30 to -20 in about 12 hours. It looks like I have a leak.

 

[1998Exp]

I agree, I looked at that as well.
Yesterday I put a vacuum on the system and it held at -30 PSI for a few hours. I noticed this morning that the pressure gauge was down from -30 to -20 in about 12 hours. It looks like I have a leak.

Not necessarily. Consider that it only takes a tiny fraction of an ounce of air infiltrating the system to cause the drop that you experienced - and that might have been due to a leak in the gauge or its connections. The proper way to check for leaks is to charge the system (usually just partially) and use an electronic 'sniffer', or perhaps a tracer.

 

[koda2000]

The low pressure and high pressure switches have Schrader valves underneath them. Unscrewing them does not let any refrigerant out at all.

I have seen tiny bubbles (after applying a few drops of water) leaking out of the low side Schrader valves of many vehicles I've owned. However, with the caps tightly attached none have leaked enough to cause a regular problem. An A/C guy told me it's pretty normal for these valve to leak a bit. I don't know why. Tire valves are basically the same design and they don't seem to leak very often.