A/C blows cold but with clicking sound and rpm changes (2 Viewers)

Joined
Dec 16, 2015
Messages
80
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Key West, FL
Hey all,

My A/C never worked while in Japan, but it was hardly ever an issue with the climate there. When I came back to the states, however, I got the system recharged and it has been working great ever since (year and a half). Unfortunately, the compressor started to go and finally failed while it was at a toyata shop getting other work done. They replaced the compressor and things have been great so far. Today I was parked at a buddy's house and i started to hear a ticking/clicking noise from the front of the dash. The rpms started to fluctuate and I could hear the compressor turning on and off. I've read that some compressor cycling is normal (?), but the clicking and frequency at which it cycled seemed way off. Once driving the issue went away. The next time I started her up (A/C in the on position) my rpms fluctuated WILDLY from 600-1500 RPM. I revved the gas and cycled the A/C which cleared the problem.

Any ideas on what could be causing this? I live in South Florida, so working air conditioning is a must! Please let me know if you have any advice.
 
Joined
Feb 10, 2017
Messages
1,075
Location
Seattle
In my past experience with AC fluctuations, fast cycling usually means too high or low of system pressure. Not sure if thats the same on the cruiser. If they didn't properly recharge the system it could be over or undercharged causing it but thats just a WAG.
Clicking could just be the sound of the relay but depends how loud it is?

Generally with AC on and stopped youll see the rpm sit higher than with it off to keep the compressor cycling on from bogging the motor. If its fluctuating wildly, its fluctuating with the signals that the compressor is on/off most likely. I'd bet its a charge issue.

Could also be a clogged evap or something causing it to cycle on, build pressure and then detect high pressure and cycle off repeatedly. Really hard to tell over the internet though! I'd check the high/low pressures and go from there.
 
Joined
Sep 15, 2016
Messages
696
Location
Chattanooga, TN
I agree with Wompom on this likely being a charge issue. To help you troubleshoot if it's high or low charge the following may be helpful:

If the erratic cycling only happens after the engine warms up then it's likely a high charge issue. If you are on the high side in terms of cooling system contents then as the system heats up the oil/etc. will expand and the pressure will start to go too high and trigger the shutoff.

An easy/cheap way to figure out if the fill is the problem, if you are running 134a at least, is to get a recharge kit which is just a can of 134a and a hose with a gauge on it. You can plug the hose into the low port near the compressor and then watch the gauge as the AC operates. If the charge is too high you'll see the needle on the gauge go high at the same time that the AC cuts off and then you'll see the pressure drop. That needle jump will repeat with every cycle. The reverse will happen if the AC is shutting off due to low pressure I assume though I've only personally experienced my AC pressure getting too high after Summer really brings the heat.

Secondary to the cycling issue, once your AC stays on if vent temps are warmish when the truck isn't moving but cool when you are driving then it could be a clue that you need to improve your fan clutch operation and/or clean your condenser and improve the gasket/foam around the radiator and shroud, etc.
 
Joined
Dec 16, 2015
Messages
80
Location
Key West, FL
In my past experience with AC fluctuations, fast cycling usually means too high or low of system pressure. Not sure if thats the same on the cruiser. If they didn't properly recharge the system it could be over or undercharged causing it but thats just a WAG.
Clicking could just be the sound of the relay but depends how loud it is?

Generally with AC on and stopped youll see the rpm sit higher than with it off to keep the compressor cycling on from bogging the motor. If its fluctuating wildly, its fluctuating with the signals that the compressor is on/off most likely. I'd bet its a charge issue.

Could also be a clogged evap or something causing it to cycle on, build pressure and then detect high pressure and cycle off repeatedly. Really hard to tell over the internet though! I'd check the high/low pressures and go from there.

Thanks for the direction! I read another thread that mentioned pressure, but it seemed inconclusive / not exactly the same as my issue. After reading your thoughts I think that seems like the best way to start. The ticking isn't super loud, and my guess was that it was something electrical when I first heard it (almost the sound of a light switch). I don't know if they checked the evap when I had previous work done to it, but I'll check that too. It's a '91. The only history I know on it is what's happened since I bought it in 2015, so checking that wouldn't hurt anyway.
 
Joined
Sep 15, 2016
Messages
696
Location
Chattanooga, TN
Regarding the ticking, you are probably hearing the relay or possibly relays down near the passengers foot well or behind the dash that are involved in the cycling on/off of the compressor. I noticed this when my unit started doing this after Summer temps climbed. I put one of the cheap refill kit gauges on and the let a bit of fluid out until this stopped happening. You can just use a screwdriver to release the extra system contents and it may not take much.

Disclaimer, some coolants are not as environmentally friendly as others and probably shouldn't just be released into the atmosphere, etc. You may have r12 or may need to have professional help after you diagnose the problem. I have r134a which I understand to be relatively safe so I released the small overcharge on my own without too much burden on my conscious.
 
Joined
Dec 16, 2015
Messages
80
Location
Key West, FL
I agree with Wompom on this likely being a charge issue. To help you troubleshoot if it's high or low charge the following may be helpful:

If the erratic cycling only happens after the engine warms up then it's likely a high charge issue. If you are on the high side in terms of cooling system contents then as the system heats up the oil/etc. will expand and the pressure will start to go too high and trigger the shutoff.

An easy/cheap way to figure out if the fill is the problem, if you are running 134a at least, is to get a recharge kit which is just a can of 134a and a hose with a gauge on it. You can plug the hose into the low port near the compressor and then watch the gauge as the AC operates. If the charge is too high you'll see the needle on the gauge go high at the same time that the AC cuts off and then you'll see the pressure drop. That needle jump will repeat with every cycle. The reverse will happen if the AC is shutting off due to low pressure I assume though I've only personally experienced my AC pressure getting too high after Summer really brings the heat.

Secondary to the cycling issue, once your AC stays on if vent temps are warmish when the truck isn't moving but cool when you are driving then it could be a clue that you need to improve your fan clutch operation and/or clean your condenser and improve the gasket/foam around the radiator and shroud, etc.


Very helpful thank you! I appreciate the explanation for exactly how the system works under different pressurizations. I believe i'm using 134a because when I got the system recharged they had to outfit it with new hardware. I definitely get warmer air when sitting still compared to driving, so I'll look into the fan clutch / condenser as well.
 
Joined
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Messages
696
Location
Chattanooga, TN
Hopefully you do have r134a as it means you can get any pressure issues sorted easily/cheaply and hopefully be done with that side of things.

I just went through a multi-step process to get cold vent temps at all times as my young children were getting hot during city driving. Seeing your 8 month old start to overheat is motivating! Fixing the over-pressure cycling helped keep my AC on all of the time which was great but it wasn't until I modded my fan clutch that my vent temps really dropped. Here is the primary old thread on the fan clutch mod:


Since '06 the approach has changed a bit. The two mods (then and now, for most/all clutches) are:

1- adjust the temp at which the fan clutch starts to engage
2- adjust the silicone oil weight inside the clutch to control how much air the fan move / how hard the fan engages

Most folks use anywhere from a 95 to 125 F opening temp (per the method in the above thread) and around 15k CST or higher oil weight in the current Aisin blue hub clutch. Whatever clutch you have right now can probably be adjusted and/or have it's oil changed and depending on your engine you may not even be able to run the blue hub that the 1fzfe runs,, etc. so search and you'll find a lot of good info on fan clutch modifications. If end up with a new/modern blue hub then I recommend you consider an opening temp around 120 F and 15K CST as a solid option as you wade through all of the information.
 
Joined
Mar 28, 2019
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Cullman, AL
I dont meant to thread jack but I have an 07 that is doing the exact same thing. It cycles every few minutes and my rpms go from 500 to around 800-900 constantly. I can even feel it while driving at any speed. It may be normal, I dont know, but it is definitely aggravating. My vents blow cold though regardless if it's sitting still or running down the road.

I just realized this was posted on 80 series tech. Sorry. Mods can delete it if need be.
 
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TYM4FUN

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Sacramento, CA
Very helpful thank you! I appreciate the explanation for exactly how the system works under different pressurizations. I believe i'm using 134a because when I got the system recharged they had to outfit it with new hardware. I definitely get warmer air when sitting still compared to driving, so I'll look into the fan clutch / condenser as well.

Was system pressure your cause? I have developed the same exact issue you describe.
 
Joined
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Messages
769
Location
Indiana
Wife's vehicle did this and it was because it was a couple of PSI overfilled. Easiest thing is to get a gauge and check it.
 

TYM4FUN

SILVER Star
Joined
Aug 16, 2012
Messages
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Location
Sacramento, CA
Wife's vehicle did this and it was because it was a couple of PSI overfilled. Easiest thing is to get a gauge and check it.

Thnx. Seem's about right for mine, as it it has only happened a few times when around 110f and heat soaked. I'll just poke the nipple to release some for a second or so.
 

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