A/C

[BAD454SS]

Was that guy the only one having problems? Sounds like he has a cooling issue that surfaces with the added heat of the A/C running. I read a post a while ago where somebody was having issues when he ran A/C and his fins and coils were half blocked with dirt and debris. So far for me no issues, engine temps have been the same as before, plus I have a huge Whipple intercooler in front of the condensor. I don't beat on the truck to much either when it's 100+. I have run it hard before in 110 deg at 90 and 100 mph and only thing that got a little above normal temp was transmission it was 25 degree higher than normal.

 

[mike.s]

Was that guy the only one having problems? Sounds like he has a cooling issue that surfaces with the added heat of the A/C running. I read a post a while ago where somebody was having issues when he ran A/C and his fins and coils were half blocked with dirt and debris. So far for me no issues, engine temps have been the same as before, plus I have a huge Whipple intercooler in front of the condensor. I don't beat on the truck to much either when it's 100+. I have run it hard before in 110 deg at 90 and 100 mph and only thing that got a little above normal temp was transmission it was 25 degree higher than normal.

He was the only one in our group that had the problem. I had my AC on but not full blast. Could be dirt and debris like you said.

 

[Z7What]

Glad I could help. There is a crazy amount of info on F150forum about this issue and what some have done to improve it. The resistor mod by far has been the best.

I have charged the A/C by pressures which was actually 12oz OVER what Ford says should be in the system, went back to Ford specs, had the expansion valve changed and even insulated the big line. The resistor has been the best! Best I had before was 48-55* now I get 39-41*

Wayne

 

[MTF]

Onto the good part.....

This ****** A/C is a problem for ALOT of the members on the forum. There was a couple members on the forum that thought that the 24oz that Ford says the system takes is actually low. So I had a friend of mine hook the gauges up and my pressures were low. To get my pressure to where he thought they should be we added about 16oz of 134a to the system, so IF my system had the correct 24oz before, I now have 40ish ounces. On the raining drive home from his house I got 39-42* vent temps. The next day there were back to the normal 48-52*.

The same friend that added the Freon to my truck also has a IDS system and while trying to figure out what the issue is with our A/C he try an experiment. Like me and the other members on the forum we noticed that out compressors only stay engauges for 8-10 seconds at a time. So with the IDS system he DEACTIVATED the computers control of the compressor and he tool control of it. With the computer controlling the compressor he was getting 42-46* vent temps, with him controlling the compressor he was able to get the vent temps to 19*. This is obvious to cold due to the increased chances of the evap freezing up. But we learned something! We learned that our A/C is ****** because that's how Ford wants it to be. The programmer in the computer tells the compressor to cycle to often based off the evap temp sensor. So with this new found information another member took it a pawn himself to find a solution. What he found was that if you install a 820K resistor onto the evap temp sensor it tricked the computer into thinking the air was warmer than it actually was and kept the compressor engaged long. The results were 39* vent temps.

Heres are some pics, info, & links to see what he and others have done to improve the A/C. The said part is that all Ford needs to do is to rewrite the program to let the compressor stay engaged longer but I seriously doubt we will see such update.



Chart to show resistance values and temps for different resistors
How to read this:
The values along the top are the new resistor values
The values down the left side are what the OEM Thermistor is reading
The values in the chart are what the PCM will read with the new resistor installed (ohms on left, DegF on right)



This chart is straight out of Fords Service Manual.


Links
Resistor Compressor Cycle Fix

Proof Our AC Is More Than Capable

The Story Of How Ford Gave Me The Big Ol D

How-To Make Your A/C A Little Better For Under $6

Hope you enjoy this info, if anyone has connections at Ford on a upper level please tell them we want a software update with different factors for how the evap temp sensor causes compressor cycling in conjunction to temps.

Wayne

Alright I got a 8.2K which read 8.049 on his Ohm tester that the crane tech had.
He tested a bunch of resistors with his Ohm meter because he has about a 200 of them just thrown in a bag.

I just threw it in this afternoon and while the compressor does not cycle any more.
The big line out in the engine bay is really cold and sweating all the way to the compressor and I do feel a difference with the air coming out of the vents.
Is it as cold as my old 1997 2dr. Chevy Tahoe was, NOPE!!!
Hell I used to see vapors coming out of the vents in my Tahoe. LOL

So I called the crane tech and told him I gave him the wrong numbers. After rereading Z7What's post.
I told him I needed a 8200. I know I screwed up. LOL
He said he'll have 1.2k that's about the same as a 820k for me next time I see him.

What do you guys think, can I leave the high 8.2K resistor in without burning anything up?
I understand that I may freeze the evaporator up, but I doubt it if the fan is on high.
I have almost read all the threads on F150 forum, I see the guys are using 670K to 1.2K with adding an extra 12 oz. of Freon.

I never checked AC in five years and I have all the professional tools. I even have all the professional adaptors for R12 and 134a, import and domestic.
Can someone please tell me what the high and low pressures should read. And I do understand that it's all about oz. and not so much pressures.
I just can't find what the specs are for our Raptors.
I found out that the PCM monitors the high and low sides and will shut the clutch down if either are to high.

 

[BAD454SS]

820k resistor is 820,000 ohms, your putting it in parallel with oem sensor. 820k offsets oem sensor 10 degrees. With what you have installed its offsetting way way higher it will think the box is at 140 degrees or something. It definatly will never cycle the compressor. I would remove it till you get the right one. http://www.petervis.com/electronics/Standard_Resistor_Values/820K.html

 

[MTF]

LOL, yeah I pulled it out the next morning. I will at least try the right one or close to it.
As I mentioned before, I have almost read all the threads on F150 forum,
I see the guys are using 670K to 1.2K with adding an extra 12 oz. of Freon.

 

[BAD454SS]

You could get you a 1 megaohm adjustable pot then play around with diffrent settings on the fly , next time i'm at the Electronics shop going to pick one up.

 

[MTF]

Interesting.

 

[602Raptor]

I want to do this, but am confused on which resistor to buy. I come up with all sorts of options for 820K / 820000 ohm. Can someone post a link?

 

[MTF]

I tried it, but it didn't work for me but I also did not add all the extra Freon.

But please post back if you got it working.