AC question

[garyp285]

Installed new evap, drier,while doing the blend doors. 03 2500 CC CTD
Went to get it vac and charged, and after adding freon the high side went way over 300, with the compressor running, and the tech said something is wrong, and evac'd it back out.
We did not hear the fan clutch kick in, and he did not jump the low pressure switch. He said the machine adds the freon to the high side, which I know nothing about.
I know we did not leave any plugs in the new parts, but it seems stopped up somewhere, and my searches say over charged, or the orfice, or condenser could be restricted. It did start cooling until shutdown.
Thanks for any advice, seems its one thing after another for me.

 

[K5IP]

Wow,
I don't know much about air conditioning, but adding Freon to the high side makes me suspect.

This makes me question the whole deal.

 

[phantomusa]

I have a 02 2500 and add freon from low side
The pressure from high side is way too much to get freon into the system ????
Pappy

 

[Bob4x4]

Modern ac machines charge without running the engine/compressor-it makes no diff what side the charge is pumped in.Warm the truck up before engaging the compressor to see if the fan clutch will engage.Without the fan working the ac pressures will go through the roof when not moving.

 

[garyp285]

Yes it was a brand new machine, and did not need the truck started until finished. My truck was not even warm maybe 140.
I'm supposed to go back later next week, and will make sure my truck is warmed up. In the meantime how can I check the fan clutch other than getting it to 200*
I think its getting warmer next week so that should help.
Thanks again

 

[MMeier]

With the AC engaged the fan clutch will respond regardless of engine coolant temp. With the truck running turn on AC, should hear the fan speed up some, if you have a decent scan tool, should be able to read fan RPMs as well.

 

[Bob4x4]

With the AC engaged the fan clutch will respond regardless of engine coolant temp. With the truck running turn on AC, should hear the fan speed up some, if you have a decent scan tool, should be able to read fan RPMs as well.

Not true with all years.There were some years that had a flash to correct the issue.There is also some years that have quite a bit of delay between AC pressure rise and fan turning on.The act of turning ac on does not activate the fan clutch-it is the ac pressure that is used as the trigger

 

[K5IP]

Bob 4x4. Well, guess I learns something new every day. I wonder if the flash you mention might help my 03. It seems like the fan runs often when there is no need for it, often when the AC is on, but sometimes just randomly on cool days. (not cold days).

\Rog

 

[MMeier]

Kinda on topic ... anyone recall what the deal was with a evap temp sensor needing to be relocated on some early 3rd gens ?

 

[Bob4x4]

Kinda on topic ... anyone recall what the deal was with a evap temp sensor needing to be relocated on some early 3rd gens ?

It was to correct a freeze up condition of the evaporator

 

[MMeier]

It was to correct a freeze up condition of the evaporator

Didn't have anything to do with the compressor refusing to engage under otherwise normal conditions ?

 

[Bob4x4]

Didn't have anything to do with the compressor refusing to engage under otherwise normal conditions ?

No and it did not fix all trucks that were having the freeze up issue=never made it to tsb IIRC

 

[Prairie Dog]

Bob 4x4. Well, guess I learns something new every day. I wonder if the flash you mention might help my 03. It seems like the fan runs often when there is no need for it, often when the AC is on, but sometimes just randomly on cool days. (not cold days).

\Rog

That's strange, mine never comes on without the AC activated. Even climbing mountain passes with a TT on the back it only rarely gets warm enough to come on.

 

[garyp285]

It was to correct a freeze up condition of the evaporator

I think this is whats been happening to mine in the hot summer while driving on the interstate. About once an hour the fan speed slows to almost nothing, and I turn it off for a while, and then it blows ok again.
I hope I wasn't supposed to re locate the temp sensor when I just replaced the evap doing the blend doors.

 

[Bob4x4]

I think this is whats been happening to mine in the hot summer while driving on the interstate. About once an hour the fan speed slows to almost nothing, and I turn it off for a while, and then it blows ok again.
I hope I wasn't supposed to re locate the temp sensor when I just replaced the evap doing the blend doors.

Is the fan speed changing or is the airflow changing?

 

[garyp285]

Its just the air flow, you can hear the fan trying hard to blow. I did replace the fan and resistor while doing the doors.

 

[Bob4x4]

Yup sounds like evap is freezing up

 

[garyp285]

Yup sounds like evap is freezing up

If it still freezes up after all this work is there any solution except moving the probe in the evap.

 

[K5IP]

Garyp285.
I also had the freezing evap problem. Rather than take it all apart, I decided to modify the resistance of the sensor by placing a variable resistor (potentiometer) in series with the sensor. I mounted the pot under the dash where I can adjust it to where things do not freeze.
the sensor output can be accessed at, or near connector C200, located behind the panel near the passenger foot area.
The signal return goes through connector pin 10, with a DB/GY wire. I clipped the wire and added the pot in series with the wire at that point.


I do not have the original data any longer but I think I added a 20K pot. It usually ends being set about half way, so anything above 10K should be ok. I remember posting something about this a few years ago so you might want to look through previous posts about this.

Rog

 

[garyp285]

Thank you, It's good to know the dash doesn't need to come out again.
I'll be sure and post when I get the ac going.

I really appreciate everyone thats takes time to give advice on this site.