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2003 4Runner intermittent a/c

Posted: Sat Mar 11, 2023 8:25 pm
by slowjam4
My compressor clutch clicks on every 17 seconds. When the air blows it is really cold. As far as I can tell, I only have one pressure switch. I removed the connector to the pressure switch and jumped it and it continued to cycle every 17 seconds. I reconnected the pressure switch. I put gauges on it. The ambient temperature was about 62 degrees with 85 percent humidity. The compressor clutch always clicks on at 45/105, sometime during the next 17 seconds, the compressor turns off(it is difficult to tell exactly when the clutch disengages because it doesn't make a loud sound and I can't watch it and the gauges at the same time) and the low pressure will continue to fall and the high pressure will continue to rise until they get to 20/130 then the pressures reverse and the low rises while the high falls until it gets to 45/105 where the compressor clutch clicks on again. So, every 17 seconds, the compressor clutch clicks on at 45/105. The lowest low pressure is always 20 and the highest high pressure is always 130(the compressor is never running at these levels). Could someone give me an idea of things that could cause this issue? Thanks.

Re: 2003 4Runner intermittent a/c

Posted: Sat Mar 11, 2023 11:27 pm
by tbirdtbird
Are you certain these numbers are not reversed? It seems unlikely that the hi side could rise to 130 if the comp is off.

Re: 2003 4Runner intermittent a/c

Posted: Sun Mar 12, 2023 12:08 pm
by JohnHere
First, don't jump anything. Those pressure switches are there for a very good reason. Toyota usually uses a trinary switch on their systems that monitors the low pressure and high pressure, and it also controls the fan.

Second, and perhaps most importantly, let's get the correct charge into the system first before trying to diagnose it. If you don't own the proper equipment, you'll need to take it to a reputable MVAC shop to recover the refrigerant that's in there now, evacuate, and re-charge it to the manufacturer's specifications. You should wait until the ambient temperature rises to about 80°F, though, before doing this.

The specs for your truck are 24 ounces net weight of R-134a, and 4.5 fluid ounces of PAG-46 oil.

Was the A/C system in this vehicle ever worked on before now?

Re: 2003 4Runner intermittent a/c

Posted: Sun Mar 12, 2023 1:46 pm
by slowjam4
I modified my post with new readings today. I did have the numbers reversed as to what the readings were when the clutch was engaging. The numbers today are more accurate. I only jumped the pressure switch for a few seconds to see if the switch was what was causing the compressor to cycle so quickly. When it still cycled with the switch jumped, I thought I could rule out that the switch was the issue. I bought this vehicle new in 2003 and it has 175,000 miles on it now. The ONLY issue I have ever had is that I have had to replace a relay switch for the air conditioner a couple of times, when the air conditioner quit working all together years ago. I thought the relay was the issue this time because it wasn't working at all about a month ago and the air conditioner light was flashing which is exactly the symptoms I had before when I replaced the relay switch. I replaced the relay and the light quit flashing and the air came on so I thought it was working as it should. It was very cold at the time and I only needed the air to defrost the windows. It took me a little while to realize the air was cycling on and off because it was cycling so quickly that it kept my windshield fog free. I have never had any work done on the motor or the air conditioner.

Re: 2003 4Runner intermittent a/c

Posted: Sun Mar 12, 2023 2:20 pm
by JohnHere
I think it's just low on refrigerant, probably nothing more than that.

Normally, the compressor shaft seal leaks a very small amount of refrigerant (carrying a minuscule amount of oil with it) to keep the seal lubricated. Over the years, this slight loss of refrigerant adds up to the point at which the system begins to malfunction, as you're experiencing. Your truck's A/C system holds 24 ounces of refrigerant, a relatively small amount. A two or three ounce loss (8-13 percent), certainly possible over 20 years, is significant enough to begin causing problems.

As mentioned, I recommend starting with a recovery/evacuation/recharge once the daily ambient temperatures rise into the 80°F range, and then see how it performs. Pressures alone won't tell us how much refrigerant the system contains. The refrigerant must be weighed-in, starting from a well-held vacuum.

Re: 2003 4Runner intermittent a/c

Posted: Sun Mar 12, 2023 9:36 pm
by tbirdtbird
Yikes!
1. OK John suggests to not jumper a switch (which I heartily agree) and you do it anyway.
2. He mentions that 68F is too cold to test anything (also agree) but you do anyway
3. The numbers are reversed which I figured
4. I was going to also say to wait to warmer weather and evac and recharge but the readings were messed up so I thought I'd start there
5. And he is so correct that the pressures do NOT indicate how much refrigerant you have (this is a commonplace misconception)

Right now you only have a minimal loss of refrigerant (called seasonal loss) and a very fixable problem once warmer weather gets here.
Keep it up and you will do damage to your system and make the repair more costly