Cooling fan will not kick into high sSpeed

Hi DodgeWorld,

It sounds like this fan is operating properly. From what you said, it looks like you have covered most all the bases.

If you are looking for fan to kick into a second speed, you are not going to see that. This fan is control via what is called duty cycle. That means the control module will ramp up the speed of the fan from 30%-99% depending on what the input sensors are telling it.

That means it will not just kick up the speed to HI when the compressor comes on. Please see the attachment.

In order for the fan to be on high (99%) the coolant temp needs to be around 230 degrees, AC pressure is 300 PSI, or transmission temperature is 232 degrees.

If none of these conditions are present then it will be set at a lower speed.

The fact that you can command the fan on 99% shows that the fan, wiring, and control module are capable of doing it. So the question is, are the sensors listed reading properly so that the control module knows when to tell it to go to high.

Also, when you say you can't get enough Freon in the system, have you evacuated it and pulled it into a vacuum and then recharged it?

If I am reading into what you are after, is your issue that the AC does not get that cold?

I appreciate you giving such a detailed response.

So yes the problem I’m having is with the AC not getting cold enough. Here is what happened to give all this context.

The van has dual zone AC and heat. The front was blowing out cold air while the back was blowing out luke warm air. So I changed the rear evaporator and rear expansion valve. The two lines coming off the rear evaporator was broke for about 2 weeks. After I got the rear evaporator and expansion valve installed I tried to put 41oz of Freon in myself. I could only get about 20oz in and it just quit taking it. (I was really just wanting to make sure it didn’t have a leak from my install)

I then put a vacuum pump on it and then using regulators I bled off what I think was the low pressure line because I couldn’t fit the regulator fitting on the high side because it was under the air filter and to be honest I did not want to take it off.

Okay so after vacuuming and emptying the system I starting filling it with Freon again and could only get it to take 20oz again.

That’s when a mechanic friend came over and started the whole talk about that my fan should kick on when I press the AC button to start pulling air across my condenser and that’s why the other 20oz won’t go into my system.

He put the scan tool on it and tested the fuse and relays. Then he operated the fan at both speeds.

Let's start with what the AC is actually blowing. That will effect what the issue could be. The way to test this, is put the vehicle in a shady area (not direct sunlight) and record what the ambient temp is. Then turn the AC on MAX cold and MAX blower speed and move the door to re circulation. Basically you want to get the AC blowing as cold as possible. Then put a thermometer (pictured below, you can get them for $4.00 at a parts store) in each vent and record which vent is blowing at what temp. Obviously, give it about 5-10 minutes to start blowing cold and then let the thermometer set in each vent for a couple minutes just to be sure you are getting the best reading.

Once we have each reading, we can start to get an idea about what the system is doing and then how far off the guideline each temp is. Based on the ambient (outside) temperature there is an expected temp range that you can expect.

Let's start there and then we can start to see where our issue is. Thanks

So the high pressure side was reading 175.

Low pressure 65.

Ambient Temp 73.

Thermometer reading 110.

Okay. Two issues. First, your pressure is high for that ambient temp. At 70 degrees you should be no higher than 40-45 on the low side and 170 on the high side.

I know you said that you could only get 20 oz in the system but are you sure you recovered it all? When you say you pulled it into a vacuum, did you actually recover the Freon or just pull it into a vacuum?

Second, where did you measure 110 degrees? Out of which vent? That sounds like the heat is on not AC. You may have a blend door issue not just an AC issue. There is just no way the AC would blow 110 degrees with an ambient temp of 73.

I would suggest having your friend come back with the scan tool and look at the HVAC door operation. He should be able to command each door through its full travel.

Assuming your AC being slightly overcharged is not keeping it from blowing cold in the front, I would address the potential blend door issue first.

Just to address your initial statement of the cooling fan being the issue, it is not likely that the cooling fan not cooling the Freon is your issue. Again, it is because if your AC system was just not getting cold, your vents would be blowing close, if not just below ambient temp. The fact that is it so high leads me to think the blend door is routing the air over the heater core rather than just the evaporator.

I included the procedure on how to replace the blend door actuators for the front and rear. I believe your issue, you said was in the rear so check the operation of that door and go from there.

Let me know what you find and we can go back to the potentially overcharged Freon issue.

I put the thermometer in the front vent near the radio.

When I would rev the motor to 2,500 the air would cool down to around 80.

I have two questions:

1. Would breaking the high and low AC lines remove all Freon?

2. Can the compressor spin without actually working?

I regulators read those pressures while the car was revved up to 2,500 rpm's.

Without Rev it was LP 70-80
And the HP 120ish.

1. Yes. Breaking the line will vent the system but this is not a good idea. Not only is it actually illegal but it is not that safe. It is under pretty good pressure so it releases the Freon, oil, and dye very aggressively. Plus it gets everywhere and is not that easy to clean up.

2. Yes. The compressor can spin without doing anything however, your compressor is building pressure but it appears it is not acting properly. According to this AC chart, at around 70-75 degrees your low should be 35-40 and the high should be no lower than 145 psi. When the low side is higher and the high side is lower than spec, it indicates the compressor is not functioning properly.

You should be reading pressure at idle. You only bring the idle up to about 1400 when you are trying to fill the system if it is not pulling in the rest of the Freon.

So as a recap:

When this all started the rear vents (driver seat back) blew lukewarm air. I evacuated the system and changed the rear expansion valve and rear evaporator. Ran a vacuum and then I could only get two cans of 12oz Freon in the system.

I then changed the cooling fan module and checked the relays and fuses. That all was good. We were able to control the fan at high and low with the engine off.

Then the regulators were showing that the low pressure was high and the high pressure was about right.

I then evacuated the system, removed the compressor, dryer, and front expansion valve. I did not remove the rear expansion valve because I changed it a few weeks ago. (I did break the lines off of it below the expansion valve. I used a professional flush kit on the system with the lines broke.

I changed the compressor, dryer, front expansion valve, and O-Rings. I did not put any oil in the dryer but certain I put the correct amount in the compressor. I then pulled a vacuum for a little over 40 minutes and then started to put Freon back in. The low and high pressures were perfect up until I started to put the third can in, then they started to go up. The system holds 2.53 lbs or 41 ounce. I had put 2 (12 oz) cans in with the right pressures.

I did check the pressure switch on the dryer to make sure it works correctly. When I unplugged it the low pressure went up by a lot.

It was 73 degrees that evening and the thermometer on the front center vent read 70 degrees and I could not get it to go any lower. When I drove home that night it went down to 50 degrees.

Now I do not know what to do.

I am concerned with the fact that you can't get the proper amount of Freon in the system. Were you not able to get more in or did you just stop because your pressure was getting too high?

Let's just get the high and low pressure as it sits today with the engine running, AC on, get pressure with clutch engaged and then what they are static.

The fact that it gets down to the proper temp (50 degrees) when driving indicates low air flow over the condenser. However, if your Freon is low, we need to correct that first.

If your pressure is getting to high when adding the proper amount, that indicates a restriction in the system. So when you say they were getting to high, what did they get up to? We need to have the proper pressure with the proper amount of Freon, Just having the proper pressure is not going to allow the system to operate if there is not enough Freon.

Let me know the pressures, meaning actual PSI readings, and temp when taken and we can go from there.

I will do that this evening when I get home from work. Again thanks for all the help.

Also, there is right around 41 ounces of Freon in the system right now. Anything past two cans takes a long time to put in, but like I said right around 41 ounces is put in.

Ill get that info tonight and probably respond first thing in the morning, because my internet at home is not very good, so I'll do it at work.

thanks,

Okay. Great. If you got 41-ish in there then that is just fine. I think the pressures with a full system will tell us what is happening. I will wait to hear back. Thanks!

Okay, so I checked the pressures as soon as I got home.
The first picture is what is what after I hooked up the gauges. I left them on there for about 10 minutes.

I put in around 5-8 ounces and the next pictures are when it was cycling. The pressures went up after I put the additional Freon in it. (Makes me wonder if there is a leak. I changed everything this past Saturday. The thermometer was reading 80 degrees in the front vent.

It was 63 degrees when I did this. From the chart the pressure was right on.

Just so I am clear on the pictures. The first is when the AC is off or static? The next picture is static after you added Freon? The third picture is after you added Freon and the compressor is on?

If so, it does look like you have a leak.

Here is what I want to look at since you have a nice gauge set. You gauge should have a temp scale on the gauge that corresponds with the pressure. So hook up your gauge set again, and look at the static pressure, AC off. Then see what your ambient temp is and your needle should be on that ambient temp on the temp scale. This is how you know that you have the proper static pressure based on your current situation. Also, both gauges should read about equal pressure while static.

I suspect you will find after you added more Freon that it is low again. If so, you have a leak.

Okay, so here is the final chapter of the vans AC issue:

I did have a leak in the front Expansion Valve and on the compressor (I forgot to add two o-rings.) I fixed that and my pressures were dialed in, but the thermometer was still reading around 55-60. I gave up and took into the dodge garage evacuated the system, pulled vacuum, recharged it.

You will never believe what the issue what my problem was after the leak was fixed. My thermometer was bad. It was reading around 10 degrees off.

So I believe that the root issue was a weak compressor and then I had the leak.

I cannot thank you enough for all your advice throughout this. I wrote the mechanic two pages of everything I did. They did the whole thing free of charge. I think they felt bad for me, lol.

Thanks again.

HAHA. That is great. You just can't make it up.

The silver lining is, you found the trick to free automotive service. Spend a lot of time, money, and tears trying to fix something. Then give the story to a shop and they will do it for free! If that is the case, I have a lot of free service coming my way.

Thanks for posting the resolution. Your adventure will surely help others that visit the site. Thanks again.