A/C Temperature Question - Compressor Cycling

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unixadm

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I have a 2005 4Runner Limited V8 AWD. I have had problems with the A/C since buying the vehicle in 02/10. After limping through last summer I decided to dig into it. The system was over charged with refrigerant. So after getting that corrected and eliminating the excessively high head pressure, the A/C systems to be cooling fairly well.

My only other Toyota for comparison was my 2001 Tundra Limited. It would blow very cold air and not cycle much. In my 4Runner it blows cold but not quite as cold as my Tundra. It still cycles the compressor which I think is the result of the evaporator temperature sensor. I'm getting around 46 degree air out of the center vents on LO - no matter the charge level I cannot get it any lower. Does anyone have any measurements to see if the cooling performance I'm seeing is around where I need to be? During my testing the ambient temperature was around 90 degrees.
 
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I'm no mechanic, but from past vehicle issues and the limited knowledge I do have of vehicle AC systems...most...if not all..vehicle A/C compressors cycle. They have pressure switches that cycle the compressors clutch so that it doesn't freeze up from running continuously.

I've never measured mine, but now I'm curious. 46 degrees seems to be pretty cold :shrug: and a 46 to 90 degree temperature differential seems substantial.
 
You are correct, all Air Conditioning systems cycle to prevent evaporater freezing and relieve pressure built up in the system as the compressor does its job. 46* sounds pretty good from a HVAC standpoint, most systems don't like going below 40-ish to prevent freezing.
 
General rule of thumb is about 30* below ambient temp. The coldest ive temped mine at was 41 and it was only 62 outside that day.
 
Had compressor go out on my V8 last year. Cost me about $2,000. I thought it was starting to make more noise than usual. Then one day the evapoator froze up. That was the end. They have a magnetic clutch. When that goes your done.
 
Thanks for the input. I know cycling is normal, however when it was overcharged the cycling was excessive with poor cooling performance. I don't have another 4Runner to baseline the HVAC performance and the cycling of the compressor is higher on this vehicle than any of my past 25 I've owned. So I figured I'd just check and see.

I'll wait for the ambient temperatures to come up and see what the cooling performance is once temps get into the mid 90's. I was simply trying to make the determination if I should evacuate the system, pull a vacuum on it for a couple of hours, and then recharge it with 22 oz of new refrigerant or leave it as is. I'll stay in a holding pattern until I can test further. Pressures look good and my compressor is quiet. The overly aggressive idle up for the compressor makes the cycling more noticeable in my 4Runner.
 
PWD4 said:
Had compressor go out on my V8 last year. Cost me about $2,000. I thought it was starting to make more noise than usual. Then one day the evapoator froze up. That was the end. They have a magnetic clutch. When that goes your done.
Click to expand...

Thread's about 9 days old now, but I was just going through the 4th gen section posts...

$2,000!!!!!!!! Good lord! Seems a bit pricey. Did you look into an aftermarket compressor, or a OEM compressor and having an independant A/C shop install?

With the cooler weather here, mine seems to cycle on/off about every 30 seconds or so, which makes me nervous for the clutch, so I try to use it very sparingly - which brings me to a complaint: I hate the fact that the a/c seems to be on with the defrost no matter what. If I have it on defrost/floor with the a/c light OFF, the compressor still runs as if the a/c light was on. My wife's G6 is this way as well and I hate it. I understand it's a safety thing because most people either don't know to turn on the a/c with the defrost to eliminate fog, but I hate it because I like the def/floor setting for the wintertime as my usual setting, but I don't want to run the compressor all the time.

I also hate that when you hit the "auto" button to use the auto climate control, the a/c always needs to come on with it...

Sorry - just my complaint for the day. Does anyone think that when it's below 70 degrees outside, that the compressor cycling every 30 seconds or so is "too often"? (Just looking to hear that it's normal is all I guess).
 
Correction, temp was around 71 on way home from work, but wife wanted a/c, so we set at 69 deg with fresh air. Every stop light, the a/c would continually cycle about 10 secs on, 8 secs or so off. Sometimes it would stay on for around 20 secs or so but would always cycle back off for around 8 seconds or so...

This bothers me and I hate having the a/c on as a result because I feel like I'm damaging/wearing on the compressor. Am I overly anal/concerned for no reason or should I have it checked out?

Like I said, its plenty cold, and maybe if it was hotter out it eould stay on longer?

Sent from my LS670 using Tapatalk
 
old thread, but did u hv any closure on this issue?...the a/c on my truck isnt as cold as that on my rav4...and always seems to cycle evry 10 secs or so @ startup
 
Reviving an old thread.

What is the cause if the compressor runs continuously, without cycling?
The compressor runs continuously even when the temp is turned to either COLD or HOT.

Thanks.
 
HiluxSurf SSR-G said:
Reviving an old thread.

What is the cause if the compressor runs continuously, without cycling?
The compressor runs continuously even when the temp is turned to either COLD or HOT.

Thanks.
Click to expand...

Could be your A/C amplifier a.k.a. HVAC Temperature Control Module / 88650-35250 / 88650-3260 or the A/C Relay
 
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