AC Compressor Turns off/on Sporadically

J

jdwk

So with the AC button pushed in, light on, temp all the way to cold, fan at 1-4, and vent at face only, the AC compressor clicks on sporadically. It blew warm air the whole way home today. So I popped the hood when I got home and watched it in my garage for a while. The compressor came on for a few seconds, low pressure tube would get cold, then it turned itself off again. Definitely more off time than on time.

I then decided to go play with it some more after letting the car cool for a while and it came on as soon as I started the car and stayed on. I then drove around the block a few times and it was as cold as ever. Never seemed to cut out.

Any idea why it would be turning itself off? The only thing I can think of is that it was very warm on the way home and the car might have been shutting it off to cool itself down as the temp gauge was reading high of center. If that is the case, I am going to have problems as it's just starting to warm up here in Phoenix.
 
Sounds like its low on freon (sp?) which causes the compressor to click on and off. just a thought though

Nick
 
Technically its not freon..Its Refrigerant....
Freon i a brand name of R22...these cars use R134a.

But yes..If these cars are equipped with a low pressure cut off..you could be cycling on that if the outdoor temps were low and the refrigerant was low.

But I would have to actually see whats going on to diagnose it personally.
 
speednv said:
do an a/c recharge and re-check it
Click to expand...
DO you even know how to do this?

If he would simply have the Charge checked..you could eliminate the need to charge at all if thats not the problem.

Don't fix it if it isn't broken.

Noob.
 
ForceFed said:
DO you even know how to do this?

If he would simply have the Charge checked..you could eliminate the need to charge at all if thats not the problem.

Don't fix it if it isn't broken.

Noob.
Click to expand...

I second this, recharging you ac system is extremely dangerous, know a couple guys recharging there system and the canister blew up. Best to take it in, freakin expensive though.

Nick
 
spud321x said:
I second this, recharging you ac system is extremely dangerous, know a couple guys recharging there system and the canister blew up. Best to take it in, freakin expensive though.

Nick
Click to expand...
Its not dangerous at all man..WTH are you talking about as well...If someone had theirs explode..It would be the first I have EVER heard of this.
Ever.

It would be almost IMPOSSIBLE to have a cylinder Explode while charging.
Period.

But it does have its inherent dangers..but risk of Explosion is not one of them.

Frostbite and a simple mistake of over or undercharge do come to mind though.
 
Thanks for the replies.
I bought an AC pressure gauge. On the low side, the pressure drops to a normal 30-45 psi when the compressor is running. When it turns off it jumps to 65, which I believe is perfectly normal operation according to the instructions.

I didn't get the readings until tonight though and its cooled off and working fine. I'll need to try it again tomorrow when its hot and actually doing the sporadic on and off. I am pretty certain it has to do with the heat, since it seems to only behave like this during the day.

Is low pressure the only thing that could be turning it off? Or are there any other kind of sensors that could cause it to switch off?
 
well if it is low during the day then you need to recharge it.... i ouly said to do that cuz i thought you could do it.... i just do it at work.... i work for mazda in SLC
 
does the light go on off on the AC button? It's known to do that on 2 and 3. If so, it's the corrosion on the connectors
 
No the light stays on steadily.

I highly doubt I will get much different pressure readings during the day. It's not like R134a can magically leak out during the day and find it's way back in at night. I have to pick the girlfriend up from the airport tomorrow, should be plenty hot by then, so I'll bring the pressure gauge along with me. She probably won't appreciate the lack of AC, but at least its not 115 yet.
 
No..but now that you say its doing it during the day..It could be tripping on high limit if there is one.

When you add heat, the pressure of the refrigerant increase....It has a Tamperature Glide that is relative to heat.

Increased heat(load) causes higher pressures.

I wish I knew a bit more about the Protege AC system..but I have never looked into it as I have never needed to work on one.

I do Commercial HVAC for a living ...so yeah...I know a little bit about the subject....Cars are no different..just slightly different components...Everything Operates the same pretty much.
 
It doesn't seem like it could be a high pressure limit. With the compressor off I see the same high pressure (65+) on both sides. When it turns on I see the low side drop gradually for a few seconds then it clicks off. There would need to be some time delay for a high pressure threshold to work, since it's already very high before it turns on. But I do agree heat would increase the pressure.

I'll try get the exact pressure numbers for you on both sides today as it's doing its thing. Thanks for you help.
 
Not true..THere is two sides to a System..High and alow...when the low pressure side is dropping....what do you think the high pressure side does...It increases.
What you are seeing at a stand still is equalized pressure and is nornmal.
THere could ba lot of thing going on causeing this..It could be a restriction in a component somewhere causing a blockage which will drop your low side and make the high side skyrocket and cut out..There is a lot that "Could" be going on...But with looking at it..I can't help you from here.

Most likely..you are gonna need to let someone with some experience in your area take a look.
You might have to pay for a diagnosis..and if you trust that diagnosis..I might be able to walk you through repairing it yourself....But you will nees to source a few things to do so..and I don't know if you will be able to since the hardest thing for you to get ahold of will be a vacuum pump...They are not cheap...and people don't typically lend them out.
 
Yeah I see what you mean, unfortunately the pressure gauge only fits the low side. I actually took a stop watch out and measured each click on and off, and it's exactly 10 seconds on, 10 seconds off. Seemed more sporadic the other day, but maybe I just wasn't paying that close attention to the intervals.

The pressure looks fine. Earlier in the day (in the 80s) the low side would sit dead center in the blue zone on the gauge (25-40psi) when the compressor was on, with it off it was 65psi exactly. During the hottest (96 deg) part of the day, the low was closer to 40psi when on, the when the compressor clicked off it would slowly rise to about 70psi before it clicked back on again. Once it clicked on, it would drop to 35psi fairly quick (3 seconds), and then sit there pretty steady for the remainder of the 10 seconds.

Now if it is due to the high side pressure being too high when the compressor is on, is it strange that the interval is exactly 10 seconds?

Would I be able to find a high side pressure gauge to test this out?
 
with the car off, both high and low side should read pretty close to eachother, and they should be fairly close to the temp outside. Is your compressor kicking on and off really fast? is that what your saying? Or are you saying its staying off to long? If it cycles fast- good possibilty you are under-charged and therefore you have a leak somewhere. when the system is over-filled, the compressor will run a long time and turn off for quite sometime. What you need is a manifold gauge set- or just bite the balls and bring it in and let someone whos certified in handling that s*** take care of it- that and we dont want EPA finding out about you blowing refrigerant into the atmosphere haha. Good luck tho.
 
Yeah I found the service manual off of pulledover's site and read how to really diagnose everything. I believe when it was kicking on and off last night when I had the stopwatch it was working properly, and just had stabilized, because the air blowing was fairly cold.
I am going to have to wait till I get another day hot enough for it too start acting up again. I am leaning towards it having too much refrigerant and tripping the pressure sensor only when it is incredibly hot out. According to the manual, this car needs to be a little lower than my gauge suggests. The blue (good) zone on my gauge is 25-40, but the manual says the low side should be 15-30.
I guess it wouldn't hurt to drop by Mazda and have them release a few psi of 134a the right way.

I'll post back when I figure it out. This manual is really awesome. Only thing I haven't been able to figure out is how the AC knows its stable. Must be a thermometer somewhere.
 
Ok first off when the compressor starts does the left hand condenser/radiator fan start if it doesnt then that is your problem time period of 10 seconds is enough time to build pressure and trip limit switch which is set at 325psi to open and stop release compressor clutch. and will close at 175psi easy when to check if it is high pressure if fan is running is to feel liguid line (smaller line going to firewall if its very hot high head pressure it should just be warm on a 80 degree day. By the way its Dichlorofluoromenthane not freon.
 
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Also the pressure in automotive air is based on RPM you should see 10-15psi at 3500 rpm and 35 at idle what turns off compressor during normal operating conditions with correct charge is a freeze stat mounted by the evaporator I think your fan isnt coming on though the reason it works sometimes is because engine temp fan is starting periodically check it out let me know
 
Good point...You obviouy know these systems better than me...and I forgot you were a tech as well..LOL.
Listen to this guy..He has a few years on me and most likely 10 more trips around the block....

Now..lets talk about automotive knowledge...(evil)
 
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