A/C question

Reply Subscribe

Thread Tools

Search this Thread

Jul 21, 2016 | 06:20 PM

04superduty6.0

Thread Starter

Senior User

Joined: Mar 2015

Posts: 156

Likes: 0

From: Spiro

A/C question

I have an 04 F350 and I was wondering if the fan is supposed to be locked up when the A/C is on. In max A/C with the fan on 3 it's barely keeping cool in the 95 degree heat we have been having. If I rev the engine I don't hear the fan noise like I do when the coolant temp hits 218 and the fan roars. Freon was replaced several months ago, along with receiver/dryer and orifice tube when I did the HG's. The A/C shop drew a vacume and did not find any leaks.

Jul 21, 2016 | 07:07 PM

mustang_309

Logistics Pro

Joined: Dec 2004

Posts: 4,138

Likes: 7

From: South Weber, Utah

Quote:

Originally Posted by 04superduty6.0

Have you ever cleaned the condenser coil? It's the first one behind the grille and catches all the bugs and dirt. If you haven't, remove the grille and take the truck to the car wash and spray it out really good, just be careful not to bend the fins by getting the power washing nozzle too close.

Jul 23, 2016 | 08:08 AM

04superduty6.0

Thread Starter

Senior User

Joined: Mar 2015

Posts: 156

Likes: 0

From: Spiro

Yes, did the condenser coil when doing HG's.

Jul 23, 2016 | 08:30 AM

mustang_309

Logistics Pro

Joined: Dec 2004

Posts: 4,138

Likes: 7

From: South Weber, Utah

Quote:

Originally Posted by 04superduty6.0

Yes, did the condenser coil when doing HG's.

To be honest I don't think anyone truely knows when the clutch fan is supposed to engage, I've tried to figure it out and it doesn't make sense as the fan will lock up when you think it doesn't need to and will not lock up when you think it should.
Yesterday it locked up I had the A/C running and ECT was 198 and EOT was like 204 and ambient temp was 103 but I was doing in town stop and go traffic.

Jul 23, 2016 | 09:20 AM

04superduty6.0

Thread Starter

Senior User

Joined: Mar 2015

Posts: 156

Likes: 0

From: Spiro

Iv'e been thinking of taping into the A/C signal that tells the PCM its on and putting an electric fan with a relay in to keep air flow going nd see if the A/C blows any cooler.

Jul 23, 2016 | 09:59 AM

mustang_309

Logistics Pro

Joined: Dec 2004

Posts: 4,138

Likes: 7

From: South Weber, Utah

Quote:

Originally Posted by 04superduty6.0

Iv'e been thinking of taping into the A/C signal that tells the PCM its on and putting an electric fan with a relay in to keep air flow going nd see if the A/C blows any cooler.

I'm pretty sure there is a mod out there where you can command the clutch fan on with the use of a switch so you can lock it up in stop and go traffic.

Jul 23, 2016 | 11:27 AM

Per4mance

Logistics Pro

Joined: Mar 2013

Posts: 4,097

Likes: 23

From: Kissimmee,Fla

I'd check the A/C pressure,I found no leaks when I did mine,sure enough it was low

Trending Topics

BREAKING: Ford Drops 6.8L V8 and Standard 6.7L Power Stroke from 2027...

138

10.5k
FX4 Real-World Use

31

819
New F-250 owner, coming from GMC/thoughts

28

1.1k
My 1976 F-250

3.7k

256k
How should I fill in this gap?

23

378

Jul 23, 2016 | 11:43 AM

FiveOJester

Fleet Mechanic

Joined: Sep 2006

Posts: 1,491

Likes: 295

From: Fresno, CA

I recently figured out part of the fan clutch vs AC logic. There is a combo pressure switch/sensor on the high side of the AC (condenser). The switch is a safety that kills the compressor if the pressure gets too high. The sensor tells the ECM the actual condensing pressure and uses that info to command the fan To run at high speed. More fan airflow lowers the condensing pressure by removing more heat. A lot of others cars use this logic for cycling of electric condenser fans.

Based on what I've observed it will only use this logic at idle and it can take a minute or two for the pressure to rise and the fan to lock up to full speed. Once you start rolling it disengages the fan. I can usually hear the fan roar for a split second when taking off from a stoplight when it's hot and the AC is going.