AC Compressor not cycling off at all
 

Hi guys, I have replaced my entire AC system, with the exception of the relay, and the ambient temperature switch. The problem is that my compressor runs constantly it never cycles off. I am afraid its going to burn up my new compressor. It also causes it to overheat at idle. I replaced the entire cooling system too, so I know its not the water pump, or fan clutch, or radiator. I talked to a friend who said that there should be a thermal indication switch that turns it on and off but I read that the relay handles turning the clutch on and off on durangos. Does anybody know what actually tells the compressor to turn on and off? I know that my charge is good and that its neither over or under oiled and all the components are new. So I am thinking that its a switch or sensor problem.

Any help is appreciated.

Thanks!

Have you tried to replace the relay with another one to see if that helps your situation? Sometimes it's the small stuff that people overlook that started the problem. I am by far not an a/c guy but give it a few hours, you will have experts chiming in.

Actually funny thing is I just did that. Same problem. So, I am at square one again. I replaced the sensor that goes in the side of the expansion valve, didn't fix it. I swapped relays didn't fix it. The compressor has a connector for a rear AC system but its disconnected because mine doesn't have that. The only things I haven't replaced are the pressure switches and any other sensors/switches that I do not know of.

45autopete is the local A/C expert, wait for him to chime in and i bet you find the problem

With the way the temperature has been in the South and also here in Missouri, most compressors will not cycle at all. Just like a house A/C Unit, in this heat they will run and not shut off. You will not do any harm to the compressor because it is running all the time. The compressor has oil in it that helps keep it lubricated. Most likely, you will see when the weather starts to get a little cooler, your compressor will cycle off and on as needed. The Durango's are big boxes on wheels and it takes forever to cool one down and I bet that you have had your fan on it's highest setting to try to cool it off. It is like supply and demand, you are demanding a lot of your system to cool down your vehicle and in doing so, it is trying to supply all the cooling power that it has to offer. There is nothing wrong with your system and yes your engine will get hotter when at idle because it is relying on the E-fans to cool it down and when it is doing that, it is also pushing all that hot air off of the condenser towards your radiator which in turn will not cool the radiator until you start to get more air flow when you drive it.

I'm going out on a limb here but you said you replaced the Low side switch but what about the High side switch. Have you ran a pressure test on the high and low side ports?


Pete<----- I have never seen a time even when it was 110 outside that mine didn't cycle on and off. Now what you are saying makes sense however I have never seen it even one time other than a house but then again we are talking about a house (and coils which are not the same in size nor system), in fact I have never heard of a compressor on a house or business cycle on and off unless it was short cycling mostly due to high/low head or low R134. I'm going the other way on this one.

A house A/C unit works basically the same as our vehicles. When you set your thermostat to a certain degree, it keeps it there by cycling off and on. A vehicle is no different in that it does basically the same thing. A person is blowing warm air past the evaporator which has the expansion valve hooked into the system. What happens in the condenser is that this hot gas is cooled to a liquid state and travels to the expansion valve. As the refrigerant goes through the expansion valve it returns to a low-pressure gas. Then it rapidly cools in the evaporator. A fan blowing over the evaporator cools the air that eventually blows out of the vents. The compressor will not cycle if it is not cool enough in the interior of the vehicle, it will run until the evaporator gets cool enough that the pressure on the low side and high side will eventually cause the compressor to cycle. The evaporator when it is being warmed by the air flowing through it will cause the low side to stay low until it can get cool enough from colder air blowing through it and that will cause the low side to climb high enough in pressure to cycle the compressor. My Durango with the front and rear air will not cycle at all until the interior is cool enough, it does cycle at night time but during the day time with the sun beating down on it, it does not cycle at all.

I would put a A/C gauge on and see what your high side pressure is. If, you see your high side exceeding 350psi. You have a problem. I would put money on the high side switch being bad on your A/C system.

Pete, a house is controlled by a thermostat that has set points. Most of these set points are 1-3 degrees differential. Depending on the type and user interface that is needed.

When the hot set point is reached a 12 volt electrical current is sent to the furnace to turn on the fan. In return the Furnace sends a signal to the compressor and the freon runs through the evaporator thus giving you the cold air.

Now the compressor will NOT shut down until the low set point is reached on the thermostat.

Example: it is 72 degrees inside the house and you want it at 70. The thermostat has a 1 degree differential. This means the furnace turns on and compressor will run continuous until the desired temperature of 70 is reached. Once it is reached it cuts the signal, the compressor turns off and the furnace fan runs for about 45 seconds to help remove any frozen ice on the evaporator and make use of the already cold evaporator. Now when the thermostat hits 71 degrees it will kick back on. If you had a 2 degree differential then the inside temp would have to hit 72 before it would turn back on and so forth.

Now those 2 are very close in main operation but not so in makeup. Now in a car there is no set point. There is only high and low pressure. The compressor engages and starts to compress the fluid, once the high side solenoid PSI is reached the compressor is turned off. Now the pressure slowly falls until the low psi set point solenoid is reached. Then when the solenoid kicks on because the PSI is too low and the compressor starts climbing in PSI again to the high side, and over and over.

Now if the members compressor isn't kicking off and everything is good I would say the high side solenoid is not turning the compressor off. But again the only way to verify this and be entirely safe is to check the PSI readings on the High and Low side and see if you are in specs.

As far as your idea, I understand, however if you can't hold PSI at all then maybe the expansion valve is worn out allowing to much too fast to run through it so it can't hold the pressure, your low on freon, or the compressor is worn.


One last thing I would do,---->jbar<---- is take the harness off the compressor and make sure the clutch is working and not froze up. But again a PSI test is your best bet on figuring out what the issue is and the safest.

45autopete is correct on this issue. If you are sitting still on a very hot day your high and low sides will never reach there cut offs due to ambient temps. Which in return your compressor isnt gona cycle. If your compressor never cycles and there is a problem it is gona push the extreme pressure out the back port on your compressor or blow a line. If the compressor is under extreme strain due to high pressure (with the hood up you will hear the sound of your compressor change ). Make it simple throw some gauges on it and you will have your answer.

I have not had the chance to get a gauge reading yet, but I probably will this weekend. The problem is that the AC never cycles off though, not even at night when the temperatures are down to the 80's. I could understand that theory during the day when its 105 outside. It has been one hot summer here in Texas, but at night it cools off pretty good and it should cycle at that point but it doesn't.

I have not had the chance to get a gauge reading yet, but I probably will this weekend. The problem is that the AC never cycles off though, not even at night when the temperatures are down to the 80's. I could understand that theory during the day when its 105 outside. It has been one hot summer here in Texas, but at night it cools off pretty good and it should cycle at that point but it doesn't.

I bet it's a high side solenoid!
It makes sense, however I have been in some REALLY hot weather and have NEVER seen the issue. So if it is "then it is" I just have my own opinion on this and I agree to dissagree with you agreeably. Also I talked about the differences in home and auto A/C.

Wait until the night when its cooler, turn ur air on full blast for about 10 minutes and let the system get cold then turn your ac on its lowest blowing setting and if your compressor doesn't cycle then you have a problem.

And i have to agree it has definitely been hot in Texas this year. I redone my wifes system and im pretty pleased with it. Sitting at idle it blows about 48-50 moving or reved it blows 38-40 regarless if its 108 or not.

Ok So this morning it was cycling correctly. Until the engine got to operating temperature than it stopped. Once the engine hit between 190 and 200 the compressor just kept running. It was only like 89 degrees outside. So I realized I have a coolant leak and filled it up with water, the engine temperature went down to 190 but the compressor still wouldn't cycle. After I drove around the block and got it to about 185 it was cycling again the engine went back up to 190 and it stopped cycling again and continued to make my truck temp rise to 205. Any suggestions? I don't understand why my engine will run normal with the AC off, I turn the AC on and it cycles properly, the engine heats up at idle and the AC stops cycling. I am guessing that I am still having an engine cooling problem but I don't know what, yeah it had a leak but I filled it up completely. I have already replaced all of the cooling components associated. Now I will find the leak but it still doesn't make sense. What temperature is the engine supposed to be at for the compressor to continue to cycle? Normal running temperature is 192 so why would that make it continuesly run?

Is the a/c not cooling when it does this? 192 is the factory t-stat that comes in most of them.

190 is the normal stat, but 2degrees shouldnt make much difference

Still sounds like your low on freon. Wrap the low side lines with foam and see if it stops, this will help ya drop about 10 degrees on the a/c if anything and the foam is really cheap!

You need to take a pressure test on hi and low ports.

Alright, so today, I evacuated the system and replaced a couple of the bolts in the expansion valve. (Lost them on original swap, and got some used ones at the salvage yard) I figured out that there was a leak there, due to makeshift bolts that I had used originally as replacements. :)

So no more leak. I currently have 200 on the high side and 45 on the low about 91 degrees outside maybe 95 was the high. AC is blowing cold, but the compressor still does not cycle off and the truck still starts to run hot if it idles too long. Talked to a guy at Firestone and he said that if its an idle only problem that it has to be airflow, (Considering I have replaced everything else) but the damn fan clutch is brand new too. It's a thermal fan clutch installed in June. I don't get it. I read somewhere else that exhaust back pressure can cause this problem too, does anyone else here know if that is true? I am pretty sure that the AC not cycling is adding to the problem, and maybe I am having an airflow problem, but do companies like 4seasons typically sell bad fan clutches off the assembly line?

So the question is....What next to test in the AC system to make sure that the compressor cycles and can a plugged exhaust system cause this too? (BTW I found out I had a coolant leak too, it was the bypass hose had a hole in the side of it but I fixed that so no more leaks anywhere, AC or coolant)

Thanks!!

John

ok exhuast backpressure would cause the truck to stall out before it caused anyother problems, as for overheating at idle check your e-fan, it should be on when the A/C is on, and when the engine temp gets over 210*, bad clutches are not common, but they are also not unheard of, you can check it by spinning it by hand, if it goes more than 1/2 a turn before stopping its not working correctly.

Well I hate to call it but I did!......LOL


As for your issue, you still didn't say you replaced the high side switch?

How can I test the switch? I know the jumper trick to bypass the switch but how do I tell if the switch is actually tripping the compressor relay on its own? Can I test it with a multimeter? and what should the readings be? I am guessing that the overheating problem is only being caused by the compressor constantly running because it doesn't have a problem in the world when its off lol. Also, if I leave the hood open today it actually held the correct temperature for 30 minutes but once I closed the hood within 5 minutes it was creeping back up to 210 again. I thought I fixed it until I closed it, with the whole coolant leak and freon leak fixed. BTW the fan clutch is good, once the engine is hot if you cut it off and try to spin the fan clutch it barely moves at all.

This model doesn't have an E-Fan, I wish it did would save me a lot of headaches. Maybe create new ones, but for now I am hating fan clutches. I have the 98 with a 318 magnum SLT.

You are correct! The 1998-1999 models never were equipped with an electric fan and in 2000 they implemented the use of them when they remodeled the engine bay. They placed a Auxiliary Fan on the back side of the radiator (which is between the clutch fan and radiator) for added cooling when the A/C is engaged or when the engine hits 210 degrees F. One of the findings of the first 2 years "teething pains" when the model came out.

Personally, I think the cooling system for the Durango is to small. If you look by comparison, the Ram radiator is larger "full sized" so the cooling is fine. Well they used the same motor with a smaller radiator and smaller intake circumference and guess what happens? It gets hot!

I fought this very problem for years when owning my Durango because it does NOT have the Electric Auxiliary Fan. Even in my V-10 I get hot with the A/C on when hot outside temps because I don't have one on it either. I have tried a clean radiator, 180 T-stat (which I recommend for your motor) and a few other things and had to come to term with that was the way it was.


For your fix, you could do 3 things:

1. Install a very thin in height electric fan with a temp controller as a pusher or;
2. Install a very thin in height electric fan with a temp controller as a puller and you will have to move the OEM fan back away from the radiator to give you room just like the 2000-2003 Durango's have.
3. Remove the clutch fan and go directly electric only like a car and some users have.

My 2002 Durango (200,000 miles) just suddenly the ac compressor is knocking quite loud, It still cools but when turned to heat still have the compressor knocking. Anybody have any ideas? Everything was just fine and then knocking. As soon as it stops raining (here in Fl) I am hoking up my guage to ac system to get reading.

My guess would be the compressor bearing is going out

I agree. I had a similar problem with a jaguar (really its a ford). The compressor was fine, it was actually the bearing in the clutch for me. Either way, sounds like you have a bearing going out, either in the compressor or the clutch.

A/c
 

My A/C is blowing hot air. I have taken it to two shops who both say the compressor is kicking on and the coolant levels were all at the right spots. It is a 2005 dodge durango, by the way. When i start the durango, the compressor comes on and will not cycle off. I get that its like supply and demand and won't kick off until the interior temperature cools off, but thats just it. The a/c is blowing hot air only, no matter how long i let it run. When i rev the engine, it makes no difference in the air. Do you have any idea on what could be causing this?

Blend door is not working properly. What year is your Durango?

It's fun reviving old threads lol. And oh my goodness as an HVAC technician seeing a lot of the misinformation presented from years ago by people made my want to pull me hair out!

How about setting the record straight then?

Please set the record straight
 

I have 03 Dodge Ram 5.7
hooked up manifold and reading were on the low side
20 and 120
and clutch was cycling on and off.

got refrigerant hooked up to yellow line but never opened low side.
readings went through the roof and compressor clutch would not disengage.

exchanged relays
checked fuses
no luck
only way to get clutch to disengage is to pull relay or shut truck off.
high side got to 350 without clutch disengaging so I **** it down.


only thing I can think is pressure switch just happen to go in that time from checking pressure to hooking up refrigerant to manifold.

houses are 24v
Everybody needs to stop saying “Freon”
there should never be ice on an evaporator unless you have a problem.
There are other things I question as well about the car systems but I’m not confident enough in my opinion to call anybody out.

Not really that much stuff actually now that I reread the whole thread again.
and just to clarify I am a house and building hvac technician, buildings and cars have several differences. The basic principles are the same but with issues like the original poster from 9 years ago had my knowledge doesn’t go too far.

yes "Freon" is an outdated term, but it has come be used as a catch all term for refrigerant . . . . its kinda like calling a tissue a kleenex . . . . wrong, but everyone knows what you mean.

2007 dodge ram 1500
 

I know it's been a while since this thread was started, but I have a similar issue with my 2007 dodge ram 1500 5.7. I have replaced the condencer, evaporator, dryer, and ac compressor twice now. The compressor seems to be constantly running even with the ac off. The only way I can get the clutch to disengage is if I pull the plug. Any suggestions?

Does the compressor run, even with the climate controlled turned completely off?

yes, with everything completely off she still engages. When I unplug it I can turn the pully and clutch separately so I know its not locked up yet.

Hhhmmm..... I don't know how the clutch on yours is wired..... Pretty sure it is controlled by the PCM though..... Likely a relay in the TIPM for it..... wonder if the control wire for that relay is grounding out somewhere, or the relay has just gone bad.

So I had the TIPM rebuilt shortly before I noticed this problem, I brought it back to the shop and they confirmed the TIPM is the problem, however, they cannot get a hold of the company that rebuilt it in order to fix it. In the mean time, someone suggested that I run a toggle switch to the compressor so I can turn it on and off manually. is that a good idea or am I still going to blow my compressor if I let it run too much?