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Discussion Starter #1
I have a 2007 Rav4 with 42K miles and a 4 cyl. I recently noticed that at idle, I feel the engine speed change every 20 sec. or so. The other day and opened the hood and noticed that the fans would come on and run for 20 seconds then shut down for 15 or 20 seconds then startup again. I can't tell for sure but I think the fans are running in conjunction with the AC compressor. I think it is cycling on and off too. I get cold air from the ac and that seems to be okay. It's the cycling on and off that's driving me nuts. I did check other posts and saw variations of this issue, but not as I have described it unless I missed something. Any insight would be appreciated before I take it to the stealer.

Kirk
 

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This sounds like the AC system may be overfilled. That would be the first thing I would check. I can't think of another likely scenario other than the pressure switch cutting the compressor off. Fuses etc should be all or nothing or at least something more random if it was a wiring issue. If you have an ac manifold set, you could check the pressures but I am not sure I would go beyond that.
 

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Discussion Starter #4
Thanks for hte repoly. That's kind of what I was thinking too. I'm bringing it to the stealer today, so I'll post the outcome.
This sounds like the AC system may be overfilled. That would be the first thing I would check. I can't think of another likely scenario other than the pressure switch cutting the compressor off. Fuses etc should be all or nothing or at least something more random if it was a wiring issue. If you have an ac manifold set, you could check the pressures but I am not sure I would go beyond that.
 

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This sounds like the AC system may be overfilled. That would be the first thing I would check. I can't think of another likely scenario other than the pressure switch cutting the compressor off. Fuses etc should be all or nothing or at least something more random if it was a wiring issue. If you have an ac manifold set, you could check the pressures but I am not sure I would go beyond that.
In order for it to be overfilled, wouldn't someone have "overfilled" it pretty recently? I thought that too, but then the op didn't mention a recent service.
 

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Discussion Starter #6
I bought the car used a couple of months ago from a dealer and I don't have any records indicating it was done. With all of these do it yourself refill kits out there, i wouldn't be surprised if someone wanted to make the ac colder. I hear the gauges on the do it yourself kit aren't all that accurate. The AC is blowing very cold right now. I had someone else telling me it was under filled. i would think if it was underfilled the compressor would run loger. Is that a correct assumption?
In order for it to be overfilled, wouldn't someone have "overfilled" it pretty recently? I thought that too, but then the op didn't mention a recent service.
 

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I bought the car used a couple of months ago from a dealer and I don't have any records indicating it was done. With all of these do it yourself refill kits out there, i wouldn't be surprised if someone wanted to make the ac colder. I hear the gauges on the do it yourself kit aren't all that accurate. The AC is blowing very cold right now. I had someone else telling me it was under filled. i would think if it was underfilled the compressor would run loger. Is that a correct assumption?
There is a low-refrigerant cut off switch that would prevent the compressor from operating at all, so I wouldn't expect that to be the case. IMO, unless you spent a good buck on a set of gauges, I wouldn't trust them. I'd either go to the dealer like you mentioned, or a local AC shop if there's one around you.
Let us know how you make out.
 

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Does your RAV have electric radiator fans. IIRC mine does. A elctric radiator fan will cycle on and off based on the temp reading of the coolant.
 

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Discussion Starter #10
Okay..had it at the dealer today. Of course when I get it there they can't see the fans running on and off. They brought me out to the shop and sure enough, all is good. The checked the system and it was low on refrigerant. So they evacuated and refilled the system to spec and added leak detector. They checked for leaks, all okay and I'm out the door. They said if there was an issue with the fans this would take care of it. On the way home I noticed the fans turning on and off. Pull into the driveway open the hood and sure enough. Fans are turning on and off every 20 seconds at idle. Arghhh! I'm starting to think there is nothing wrong with the system.
 

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Okay..had it at the dealer today. Of course when I get it there they can't see the fans running on and off. They brought me out to the shop and sure enough, all is good. The checked the system and it was low on refrigerant. So they evacuated and refilled the system to spec and added leak detector. They checked for leaks, all okay and I'm out the door. They said if there was an issue with the fans this would take care of it. On the way home I noticed the fans turning on and off. Pull into the driveway open the hood and sure enough. Fans are turning on and off every 20 seconds at idle. Arghhh! I'm starting to think there is nothing wrong with the system.
I always thought the fans ran constantly, as long as the compressor was running, but I could be wrong. When I get a chance, I'll go out and check mine. Every 20 secs doesn't sound right to me.
 

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kirkster: Just went outside and checked mine. Started it up cold, no fans running. Put AC on, fans running. Ran about 2-3 minutes, comp cuts off, fans off too, minute later comp on, fans on. Comp and fans run for about 3-4 min when I shut off AC. Comp and fans off. So, fans run whenever compressor is running(as well as when the engine gets hot, but that's on a different "schedule").
You would need to determine if the compressor is cycling on and off at the same time as the fans. If the comp is cycling every 20 secs, that's a definite problem. If the comp is staying on while the fans cycle every 20 secs, that would indicate a problem with the fan control circuit.
Hope this makes sense to you!
 

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Discussion Starter #13
My brother is a mechanic and he's telling me now that the weather is cooler they don't run as long. It's like in the high 60's here today. When stopped or at idle, the fans will run more because heat builds up. I'm kind of feeling like, what is the point? I had a 1999 Rav4 prior to this one and I know the fans cycled, just not as frequently. I can't remember if they cycled when it was hot.
If you could let me know, that would be great. Car needs to be totally warmed up.


I always thought the fans ran constantly, as long as the compressor was running, but I could be wrong. When I get a chance, I'll go out and check mine. Every 20 secs doesn't sound right to me.
 

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My brother is a mechanic and he's telling me now that the weather is cooler they don't run as long. It's like in the high 60's here today. When stopped or at idle, the fans will run more because heat builds up. I'm kind of feeling like, what is the point? I had a 1999 Rav4 prior to this one and I know the fans cycled, just not as frequently. I can't remember if they cycled when it was hot.
If you could let me know, that would be great. Car needs to be totally warmed up.
see my previous post at 11:23 today......
 

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Discussion Starter #15
Thanks for the info. This is helpful to know. I used my phone to video the issue and e-mailed it to the dealer so the tech could look at it before I go back on Monday. Hoping to get the mystery solved soon. Thanks again. Kirk


kirkster: Just went outside and checked mine. Started it up cold, no fans running. Put AC on, fans running. Ran about 2-3 minutes, comp cuts off, fans off too, minute later comp on, fans on. Comp and fans run for about 3-4 min when I shut off AC. Comp and fans off. So, fans run whenever compressor is running(as well as when the engine gets hot, but that's on a different "schedule").
You would need to determine if the compressor is cycling on and off at the same time as the fans. If the comp is cycling every 20 secs, that's a definite problem. If the comp is staying on while the fans cycle every 20 secs, that would indicate a problem with the fan control circuit.
Hope this makes sense to you!
 

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What speed is your blower running on.?

If the air flow across the evaporater is slow, it's temperature can drop towards the freezing point. The compressor will shut off at this point to prevent icing. As the 60 degree ambient air flows across the evaporater, it's temperature will rise again and the compresser will start up again. The cycle will continue.

I believe it is possible that earlier in the year, ambient temperatures were higher, and you ran the blower at higher speeds. These two things would have reduced evaporater icing.

Try running the blower at maximum speed, to warm the evaporater as much as possible, and see if the symptoms change.
 

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I haven't poured thru all the posts & details but I'm thinking that unless the A/C has actually stopped working at some point, there's nothing wrong.
 

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Discussion Starter #19
I will give it a try. Thanks... Check out the clip I posted in a post I just did.


What speed is your blower running on.?

If the air flow across the evaporater is slow, it's temperature can drop towards the freezing point. The compressor will shut off at this point to prevent icing. As the 60 degree ambient air flows across the evaporater, it's temperature will rise again and the compresser will start up again. The cycle will continue.

I believe it is possible that earlier in the year, ambient temperatures were higher, and you ran the blower at higher speeds. These two things would have reduced evaporater icing.

Try running the blower at maximum speed, to warm the evaporater as much as possible, and see if the symptoms change.
 

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Discussion Starter #20
I think you are on to something. I started it up today, temp was around 70F. Engaged AC and fans started the on off cycle. Blower speed was at the minimum. As soon as I had the AC on and moved the fan speed to max, the fans ran much longer. matter of fact, I watched them for over a minute. Now I'm wondering if I move the fan to half speed if that does anything. Then later in the evening I'm stopped at a drive thru, no a/c on and the fan turned on, ran for about 30 sec and shut off for a minute or two then came on for a bit. I'm really starting to think things are working the way they are designed to work.




What speed is your blower running on.?

If the air flow across the evaporater is slow, it's temperature can drop towards the freezing point. The compressor will shut off at this point to prevent icing. As the 60 degree ambient air flows across the evaporater, it's temperature will rise again and the compresser will start up again. The cycle will continue.

I believe it is possible that earlier in the year, ambient temperatures were higher, and you ran the blower at higher speeds. These two things would have reduced evaporater icing.

Try running the blower at maximum speed, to warm the evaporater as much as possible, and see if the symptoms change.
 
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