2004 V8 A/C On and Off - Already Replaced Relay - Any Thoughts?
- Thread starter UteRunner
- Start date
Register to hide this ad
BlackWorksInc
New member
What do you mean that it cycles on and off every 20~30 seconds? Do you mean the compressor component itself? If so that is normal operation.
If not...
Did you have the system inspected for leaks and checked if there is any refrigerant in the system? These are possibilities that could be causing your condition.
Are you putting it on Auto or manually activating the AC?
If not...
Did you have the system inspected for leaks and checked if there is any refrigerant in the system? These are possibilities that could be causing your condition.
Are you putting it on Auto or manually activating the AC?
stanleybb50
New member
Not to hijack, but similarly, when my a/c is in recirculating mode, the compressor cycles on/off like every 7 seconds when I'm at traffic lights... I hate when it does this because I don't want to wear the clutch, so I turn it to fresh air and that hot fresh air makes it stay on non-stop.
Which is the ''lesser evil''? Cycling every 7 seconds with recirc or always on with fresh?
Blackworks, you seem like our designated 'expert', so hopefully you have an opinion? Is that cycling normal? My rpm's advance/etc with each cycle. Air is nice and cold on either setting however.
**oh, and I like to manually activate my a/c to aviod the cycling. Lol I like never use the auto because I don't want to stress the system for my comfort... lol
- Sent via Tapatalk for Android
Which is the ''lesser evil''? Cycling every 7 seconds with recirc or always on with fresh?
Blackworks, you seem like our designated 'expert', so hopefully you have an opinion? Is that cycling normal? My rpm's advance/etc with each cycle. Air is nice and cold on either setting however.
**oh, and I like to manually activate my a/c to aviod the cycling. Lol I like never use the auto because I don't want to stress the system for my comfort... lol
- Sent via Tapatalk for Android
BlackWorksInc
New member
To quickly expain how a vehicle's Air Conditioning systems works: (I can go into further detail, but I'd rather just give you guys the summary unless you really want me to write a small essay LOL)
The A/C functions on thermal dynamics, heat is generated when you compress a gas, and heat is lost when you expand a gas.
The compressor is designed to cycle on and off, its part of its intended operation, it compresses the refrigerant to high pressure (roughly 100+ psi) and then that compressed gas goes into the evaporator where it expands exponentionally quickly reducing the temperature to near freezing where it is cycled through condenser to once again be pumped through the compressor.
The way the A/C system maintains the lovely frostbitten temperature that you want without freezing itself (and trust me if it didn't cycle the way it is supposed to, you could probably flash freeze beers with how cold it can potentially get... though your evaporator will be frozen by then and a few other things...) is to cycle the compressor on and off to maintain a specified pressure in the system and thus a specified temperature. (as a general rule of thumb, 1 degree of temperature will equal roughly 1 psi in an A/C at rest without the compressor being run)
The A/C is engineered to cycle on and off continiously and it is absolutely normal. Also when you put your A/C into "recirculation mode" it is using the interior air to cool off, thus allowing the A/C to cool off the air quicker, more efficiently, and cooler than it would say if it was 90 degrees outside. If you use recirulation all the time I do, please do yourself a favor and check your cabin air filter and replace it when you need it.
The A/C functions on thermal dynamics, heat is generated when you compress a gas, and heat is lost when you expand a gas.
The compressor is designed to cycle on and off, its part of its intended operation, it compresses the refrigerant to high pressure (roughly 100+ psi) and then that compressed gas goes into the evaporator where it expands exponentionally quickly reducing the temperature to near freezing where it is cycled through condenser to once again be pumped through the compressor.
The way the A/C system maintains the lovely frostbitten temperature that you want without freezing itself (and trust me if it didn't cycle the way it is supposed to, you could probably flash freeze beers with how cold it can potentially get... though your evaporator will be frozen by then and a few other things...) is to cycle the compressor on and off to maintain a specified pressure in the system and thus a specified temperature. (as a general rule of thumb, 1 degree of temperature will equal roughly 1 psi in an A/C at rest without the compressor being run)
The A/C is engineered to cycle on and off continiously and it is absolutely normal. Also when you put your A/C into "recirculation mode" it is using the interior air to cool off, thus allowing the A/C to cool off the air quicker, more efficiently, and cooler than it would say if it was 90 degrees outside. If you use recirulation all the time I do, please do yourself a favor and check your cabin air filter and replace it when you need it.
UteRunner
New member
I use only the manual setting for my a/c. I don't think I've ever used the auto feature. I understand that the compressor cycles, however, when it does the temperature of the air coming into the cabin goes from cold to warm. I have done a cursory inspection of the a/c system and could see no leaks or signs of leaks (yes I know they can be very, very small).
One thing I did see yesterday is bubbles in the sight glass. There weren't bubbles the whole time, just every 10 second or so. The compressor was on this entire time as I could see the pulley engaged. I did a whole bunch of research and concluded that the system was low on refrigerant.
Should I attempt a DIY, AutoZone style recharge kit since I don't need to vacuum and fill the whole system? The truck does have 130K miles and is 7 years old, so it seems reasonable that it is a little low just because of its age.
:thanks:
One thing I did see yesterday is bubbles in the sight glass. There weren't bubbles the whole time, just every 10 second or so. The compressor was on this entire time as I could see the pulley engaged. I did a whole bunch of research and concluded that the system was low on refrigerant.
Should I attempt a DIY, AutoZone style recharge kit since I don't need to vacuum and fill the whole system? The truck does have 130K miles and is 7 years old, so it seems reasonable that it is a little low just because of its age.
:thanks:
BlackWorksInc
New member
The best repair is going to be evacuating the system and vaccuuming it. You don't want any air in the system as air does not have the same qualities as refrigerent in the respect of compressing and expansion temperatures. Even a little air will diminish cooling performance.
I know how you feel, but somethings consumers aren't able to do by themselves. Look on the bright side though! You unlike the majority of car owners these days KNOWS how to work on their car let alone change a flat tire.
I know how you feel, but somethings consumers aren't able to do by themselves. Look on the bright side though! You unlike the majority of car owners these days KNOWS how to work on their car let alone change a flat tire.
Applying a vacuum to the A/C system is not just to remove air, it's also to remove moisture, as moisture easily boils off under vacuum, even at normal ambient temperature. This is why it is so important to apply vacuum for the proper time period to any A/C system that has been open to the atmosphere for any amount of time.
BlackWorksInc
New member
That too... Now stop making me look bad! LOL
Just kidding, but yes, moisture is also a bad thing... which reminds me... I should probably consider replacing my reciever/dryer.
Just kidding, but yes, moisture is also a bad thing... which reminds me... I should probably consider replacing my reciever/dryer.
galactic_04
New member
Just FYI, the new Toyotas don't have a clutch system in the compressor. It's always turning. Instead they use basically a servo-operated ball bearing system that opens up or closes the compression chamber for the A/C compressor. With this system there's minimal wear-parts involved. Of course the compressor is a LOT ($1000+ on a new camry)
stanleybb50
New member
Verrrry interesting and good info! If it means anything, I thought I did notice that it seems like when I first kick the a/c on manually, it seems like more of that usual compressor 'jolt' than when its cycling on its own.
Thanks for this info! I'll try to do a little more research on the subject. If I find anything else, I'll post a link.
Sounds like my t4r's 5-10 sec a/c cycling must be functioning 100% normally based on the replies and I have nothing to worry about.
Thanks BlackWorksInc also!
- Sent via Tapatalk for Android
BlackWorksInc
New member
We have weird stuff on our newer engines, pretty cool but different from what has been standard for decades in the automotive field. But that's progress...
Where did you get this info? If you're correct, that's something I didn't know about our A/C compressors. I thought we had a conventional clutch compressor, but I have to admit that I've never looked closely at it. Or are you ONLY talking about new Toyotas and not our 4Runners?
So anyway, where did you hear (or read) about this?
BlackWorksInc
New member
I believe he is talking about the new Camrys. Our 4Runners use a magnetic clutch.
stanleybb50
New member
Oh.. ok. Tomorrow, I'll pop the hood while its cycling to see if the clutch is truly engaging/disengaging with the cycles and report back.
- Sent via Tapatalk for Android
I have a similar, yet slightly different issue. My A/C controls light up and function just fine, but it does not blow any air at all. After driving for about 5-10 minutes it kicks on and starts working just fine. This issue has only occurred about 5 times in the last month or so, but is becoming more frequent. I changed the clutch relay, but that didn't do anything. It's an '03 4runner LTD V8.
Any thoughts... Thanks!
Any thoughts... Thanks!
UteRunner
New member
Temp Fluctuation
Well, after everything the temperature is still fluctuating every 30 seconds or so from warm to cold. I hate taking it in for another diagnosi$. Is there a temp sensor that could be going out?
I've also read something about a "blend door" that controls the air flow. Is there a way to check if this thing is operating correctly. I do have climate control. Could something in that system affect the temp this way?
Well, after everything the temperature is still fluctuating every 30 seconds or so from warm to cold. I hate taking it in for another diagnosi$. Is there a temp sensor that could be going out?
I've also read something about a "blend door" that controls the air flow. Is there a way to check if this thing is operating correctly. I do have climate control. Could something in that system affect the temp this way?
Last edited:
