A/C turns on and off while driving by its self.

[mosaud1998]

I have a 2011 Toyota Sienna XLE with 62k miles on it. I've been having this issue since last year where the car's A/C automatically turns on and off while I am driving.

I'll be driving normally and the A/C will automatically turn off (I'll start to feel normal air, not A/C cold air), and then a few minutes after you'll start to feel cold air again.

The cabin air filter is new and the freon level is fine. Idk if the compressor is on its way out or?

The car doesn't have an auto start/stop feature or an "Eco" mode that turns the A/C off while driving to save fuel. Neither do I keep the climate control on auto.

I am driving to New York in a week and kind of want this issue figured out myself before I pay the Toyota Dealership $75.

 

[JHZR2]

AC system powers on and off? Or the compressor clicks on and off (normal)? Or just warms up and then cools?

If powering on and off. That sounds like a harness or wiring issue.

if compresssor clicking on and off, that’s normal to an extent, but doing it too much can point to an under or over charge, or air in the system, or a few other things.

If it warms up and cools without any other observations, it may still be charge related, or control related. That’s a bit harder because it can be contingent on a number of other things, including thermal load and ambient conditions.

How did you determine that the “Freon” level was ”fine”? Static or operational test? What conditions?

So need a bit more info…

 

[mosaud1998]

AC system powers on and off? Or the compressor clicks on and off (normal)? Or just warms up and then cools?

If powering on and off. That sounds like a harness or wiring issue.

if compresssor clicking on and off, that’s normal to an extent, but doing it too much can point to an under or over charge, or air in the system, or a few other things.

If it warms up and cools without any other observations, it may still be charge related, or control related. That’s a bit harder because it can be contingent on a number of other things, including thermal load and ambient conditions.

So need a bit more info…

It warms up and cools down.

I brought a can of freon from Autozone last time this happened (summer of last year). The freon bottle came with a gauge. I measured the freon level with the gauge and it showed the freon level is full. Probably not the most accurate test but...

 

[JGmazda]

My advice for what it's worth.... Take it to a qualified AC specialist. I've "wrenched" on my cars in my life and the AC system is one of those that takes a great deal of experience and knowledge to get right. Adding a can of Freon or using a guage on the can is playing Russian Roulette. It "may" work or it may just mask the real problem. Could be anything really... not just a lack of refrigerant.

 

[grjr]

Scan the car for trouble codes, that would be a good place to start. There are quite a few items that could be disabling the AC system from functioning.

 

[ripcord]

That gauge that came with the can of refrigerant is only showing you half of the picture. You need to check both the high pressure and the low pressure side of the system under varying conditions. The low side can read fine (what you were measuring with your gauge) but that's not enough information to know if the system has an appropriate amount of refrigerant.

 

[mosaud1998]

That gauge that came with the can of refrigerant is only showing you half of the picture. You need to check both the high pressure and the low pressure side of the system under varying conditions. The low side can read fine (what you were measuring with your gauge) but that's not enough information to know if the system has an appropriate amount of refrigerant.

Either I'll take it to Toyota or have one of the techs at my job take a look at it and buy him lunch

 

[Chris142]

Replace the ac clutch relay. Common problem on these.

 

[Nick1994]

and the freon level is fine.

Says who?

 

[Oro_O]

This was a common Toyota problem in the 00s. I don't know when the revised part came out.

The issue is a defect in the a/c relay design. Popping in a new $7 relay takes care of the problem. I don't know if your 2011 Sienna has the good or bad relay (I know Lexus up through late 00s did - not sure how long it applied). The relay is in the engine fuse box and it says "mg cltch' or something like that. I don't know if there's an identical one you can swap it with, but there is a revised p/n out there for it.

 

[JHZR2]

It warms up and cools down.

I brought a can of freon from Autozone last time this happened (summer of last year). The freon bottle came with a gauge. I measured the freon level with the gauge and it showed the freon level is full. Probably not the most accurate test but...

You could have air in there.

did you take a reading from this gauge with the system static (off), or operational? Was the gauge reading correctly with the compressor on and off, cycling, at all times? Did you get a high side reading too?


Unless you purged the line correctly, you could have injected a slug of air into there too. Of course it does no cooling… and affects pressures, which causes cutouts early, and cooling cycles…

 

[mk378]

It gets cold once, so the refrigerant system is ok. There aren't gremlins under the hood taking "freon" out and putting it back to mess with your mind.

Intermittent failure of the compressor to engage means check the relay and the clutch gap.

 

[Bitter]

System needs to be evacuated, charge checked (how many lbs, not psi), vacuumed to as close to 30" as the machine will get, wait 20 min, check vacuum loss, re-vacuum (gases dissolved in the oil will come out during this time), then charged to the correct weight of R134A. Once charged, you need the system low and high side pressures checked at idle and at 2500 RPM. Often on older vehicles the lower half of the condenser has lost a lot of surface area, resulting higher than desired high side pressures which will cause the compressor to cycle off until the pressure drops, resulting in your loss of cold air for a few minutes. Blockages hindering air flow through the condenser will also cause the same situation, this is the most common thing I see causing intermittent cold/warm/cold air like you're describing. Make sure that's looked at closely. Also as mentioned, if AC work had been done before it's pretty possible that someone did not remove all the air from the system and your pressures are all messed up. Some guys will replace a part, dump in some R134A till it blows cold, and send it. This is incorrect.

The AC clutch relays would tend to fail and stay failed till they cooled off which was more than a few minutes, usually the AC would stop working on a trip and not resume until the car was shut off and parked for a period of time.

 

[wag123]

System needs to be evacuated, charge checked (how many lbs, not psi), vacuumed to as close to 30" as the machine will get, wait 20 min, check vacuum loss, re-vacuum (gases dissolved in the oil will come out during this time), then charged to the correct weight of R134A. Once charged, you need the system low and high side pressures checked at idle and at 2500 RPM. Often on older vehicles the lower half of the condenser has lost a lot of surface area, resulting higher than desired high side pressures which will cause the compressor to cycle off until the pressure drops, resulting in your loss of cold air for a few minutes. Blockages hindering air flow through the condenser will also cause the same situation, this is the most common thing I see causing intermittent cold/warm/cold air like you're describing. Make sure that's looked at closely. Also as mentioned, if AC work had been done before it's pretty possible that someone did not remove all the air from the system and your pressures are all messed up. Some guys will replace a part, dump in some R134A till it blows cold, and send it. This is incorrect.

The AC clutch relays would tend to fail and stay failed till they cooled off which was more than a few minutes, usually the AC would stop working on a trip and not resume until the car was shut off and parked for a period of time.

You also need to make sure that the cooling/condenser fans are both working properly. They both need to be running at full speed when the AC clutch is engaged.
As others have said, you need to find someone who has a proper set of AC gauges before you go any further. You need to know what is going on with the high side pressure to properly diagnose this problem.

 

[Bitter]

You also need to make sure that the cooling/condenser fans are both working properly. They both need to be running at full speed when the AC clutch is engaged.
As others have said, you need to find someone who has a proper set of AC gauges before you go any further. You need to know what is going on with the high side pressure to properly diagnose this problem.

Yes, I accidentally glossed over the fans. I kind of skip stuff when I'm thinking because it's just second nature now.

 

[tiger862]

I have seen evaporater freeze up causing this problem. So many you things to check. Seen anywhere from relay getting hot, evaporater clogged or expansion valve is bad.

 

[Bitter]

I have seen evaporater freeze up causing this problem. So many you things to check. Seen anywhere from relay getting hot, evaporater clogged or expansion valve is bad.

It can still happen but it's much less common with TXV systems than it was with orifice tube systems. Conditions have to be just right, its not the kind of thing that would normally happen every day for a long period of time with modern systems and especially not if the system has outlet air temp sense.

 

[mosaud1998]

I asked a few of my mechanic friends and there saying the A/C relay might be bad. Where the hell is the A/C relay? In the fuse box?

 

[JC1]

I asked a few of my mechanic friends and there saying the A/C relay might be bad. Where the hell is the A/C relay? In the fuse box?

This video should show you the AC relay location.

 

[Chris142]

I asked a few of my mechanic friends and there saying the A/C relay might be bad. Where the hell is the A/C relay? In the fuse box?

Yes under the hood. It may be labeled mag clutch or something similar