A/C cut out while towing
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5th Wheeling
Joined: May 2006
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A/C cut out while towing
I just started towing this heavy for long distances but 6500lb., 86* ambient, ECT=198-210, EOT= 204-220 the compressor disengages. When i get into a town and catch red lights the air comes back on. I know there is an overheating safety that will cut the air off but my temps seem normal and it won't cut off at the same temp every time. It's like I have a bad sensor but I don't know where to start. I've checked 134a psi and it is good. Any body had a problem like this?
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5th Wheeling
Joined: May 2006
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I guess I'm wondering what temp sensor would cut off the a/c. or does the pcm compute temp differences and decide to turn it off, I'm stumped. It operates fine all the time except when towing this boat.
Hotshot
Joined: Jan 2004
Posts: 19,760
Likes: 1,079
From: St Louis
Check 1) Clutch gap, 2) temp blend door, and 3) HVAC FAQs (link is in signature). Your system is almost identical (with exception to the vacuum pump) as the 1/2 tons.
It would also help if you identified your truck in your question or post by its year and specific model. There have been differences in the control circuits over the years.
Depending on the year, a scan tool may be needed to see what's going on.
It would also help if you identified your truck in your question or post by its year and specific model. There have been differences in the control circuits over the years.
Depending on the year, a scan tool may be needed to see what's going on.
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5th Wheeling
Joined: May 2006
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It is a 2003 F250 ,6.0. I haven't checked the air gap. If it is the air gap then I will still have voltage at the compressor correct? I thought it was electrical because of when it comes back on after slowing down like riding through a small town. and it's not throwing any codes.
Hotshot
Joined: Apr 2010
Posts: 19,056
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From: Saratoga Springs,UT
Low and High side R134a pressure
What was Low Side pressure??35psi???? and was the truck running with A/C )n during test
there is no overheat cutout
But there is High and low Pressure cutoffs that would stop A/C
Start the truck have someone trigger A/C compress on and off make shure you can hear the clutch turn off and on should be able to see it work to
you can also check with a DVM
I suspect its a High/low pressure cutoff since at hwy speed it cuts OFF
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5th Wheeling
Joined: May 2006
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The refrigerant psi was 220/40. I even recovered some so the head would be below 200 and it still cut off after about an hour of towing, so I set the charge back right. I had read that if the truck starts to overheat a strategy in the program will disable the a/c to keep heat from the condenser off of the radiator. sometimes after it stops for the 3rd time it won't come back on, so next time it does that I will be able to check some voltages at the high and low psi switches and at the compressor. I think if I have voltage at the compressor it will be the air gap I have read about. Thanks for you guys help! I have been able to fix or prevent every other problem with this truck from this forum for the last 205,000 miles.
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5th Wheeling
Joined: May 2006
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It doesn't have a leak, the orifice may be getting clogged but I thought that would show up all the time not just while under a heavy load.
Posting Guru
Joined: Nov 2012
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I agree with Bullit, also there used to be a Wide Open cut out switch to the throttle that would cut out A/C compressor to give full power avaialabe to the engine.
Since there is no physical throttle plate I assume this is now a software caculation noot shure tho I don't have access to Ford proprietary information.
Since there is no physical throttle plate I assume this is now a software caculation noot shure tho I don't have access to Ford proprietary information.
Hotshot
Joined: Jan 2004
Posts: 19,760
Likes: 1,079
From: St Louis
It is a 2003 F250 ,6.0. I haven't checked the air gap. If it is the air gap then I will still have voltage at the compressor correct? I thought it was electrical because of when it comes back on after slowing down like riding through a small town. and it's not throwing any codes.
The '03 does use a PCM controlled A/C clutch relay. That mean's it's software controlled.
It's never going to throw any codes, this function isn't monitored by OBDII.
I'm willing to bet that the orifice tube is getting clogged or the receiver/dryer bag might have a leak
You might be hitting 300+ psi high side at high rpm and the system is cutting out.
Check your gap first. Otherwise, you'll need the scan tool to examine PIDs to see if the noted disengagement is commanded by the PCM.
Certified Thread Hijacker
Joined: Aug 2001
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Yes, it would have voltage at the clutch whenever the PCM commanded it to be so, provided everything else is working.
The '03 does use a PCM controlled A/C clutch relay. That mean's it's software controlled.
It's never going to throw any codes, this function isn't monitored by OBDII.
There's no evidence presented to support that contention. Highly unlikely.
The high side cutout switch is usually around 465 psi ascending. This is NOT software controlled, it is a simple pressure switch. If the HPCO were activated, the system would re-energize as soon as the high side pressure dropped below the lower limit of the switch which would usually take less than a minute. It wouldn't wait for slow traffic or small towns. It would also cycle quite regularly (up to several times per minute) under most conditions.
Check your gap first. Otherwise, you'll need the scan tool to examine PIDs to see if the noted disengagement is commanded by the PCM.
The '03 does use a PCM controlled A/C clutch relay. That mean's it's software controlled.
It's never going to throw any codes, this function isn't monitored by OBDII.
There's no evidence presented to support that contention. Highly unlikely.
The high side cutout switch is usually around 465 psi ascending. This is NOT software controlled, it is a simple pressure switch. If the HPCO were activated, the system would re-energize as soon as the high side pressure dropped below the lower limit of the switch which would usually take less than a minute. It wouldn't wait for slow traffic or small towns. It would also cycle quite regularly (up to several times per minute) under most conditions.
Check your gap first. Otherwise, you'll need the scan tool to examine PIDs to see if the noted disengagement is commanded by the PCM.