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?

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

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.

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.

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.

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!

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.

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.