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AC clutch cycling on/off rapidly every ~10-15s

itch808 on Sat September 29, 2007 9:52 PM User is offline

Year: 2003
Make: Ford
Model: F-250
Engine Size: 5.4L V8
Refrigerant Type: R134
Ambient Temp: 87F
Pressure Low: 40
Pressure High: 450
Country of Origin: United States

I'm back again! Ok, my brother in law's truck was blowing warm so he did what most people do, he went to walmart and bought a re-fill kit for his AC. He charged it (I wasn't around) and he said the gauge jumped up to 100psi (on the low side with the cheapo gauge). I'm not sure how much he filled it or what not. But when he showed his car to me the AC clutch was cycling on/off like crazy, about every 10 seconds. I hooked up my manifold gauges, low side read 40-60psi as it cycled on/off and the high side was some insane ~450psi.

I've never worked on an domestic car before or any vehicle with such a large engine, but that high side pressure doesn't seem normal!!! I drained off a bit so the low side was down to a ~35psi but the high side was still reading the same thing @ 450psi. The clutch then started cycling on/off about every minute or so. Does this sound normal or is his system still overcharged? His high side is still drastically over the rough estimate of 2.5x ambient. Thanks.

iceman2555 on Sat September 29, 2007 10:50 PM User is offlineView users profile

The system should be recovered, evac and recharged to OE specs. Forget all the magic in a can kits and adding to pressures 'look' or 'seem' correct...get the system back to OE specs and then retest system...post results and let's see what is going on.....The first aspect of any A/C performance diagnosis is to know how much refrigerant and lube is in the system.......
Good Luck



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The strongest reason for the people to retain the right to keep and bear arms is, as a last resort, to protect themselves against tyranny in government.
Thomas Jefferson

Chick on Sun September 30, 2007 5:00 AM User is offlineView users profile

While it's empty, pull out the O tube and inspect it. If it's clogged, he may have caused more damage to the system by adding magic in a can..If it's clear, follow Icemans advice and pull a deep vacuum and recharge the exact amount called for into the vacuum. Don't try to charge it without pulling a vacuum, and never try "adjusting" a charge once you see a problem and know you have the right amount in there.... As stated above, you need to know how much is in there to diagnosis the system properly...Hope this helps..

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Chick
Email: Chick

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Freedoms just another word for nothing left to lose

itch808 on Mon October 01, 2007 1:06 AM User is offline

Does anyone know how many ounces his truck needs for refrig and compressor oil? Also what viscosity oil does it use? I have PAG 46 and BVA 100 lying around.

mikeal21 on Mon October 01, 2007 2:38 AM User is offline

Compressor on/off indicates low charge, mostly. Trick is low pressure gage will show high, you can't charge. Thats what I had and I wasted a can of r134, not knowing how to do it. I had to jump the compressor so the pressure would give proper psi. Something about the a/c compensating for lack of pressure, thats why it won't cycle properly. There is a clutch cycling switch that you have to jump, I used simple light tester to determine what wire was used to cycle clutch. Put a + charge to it, kicked it on. And bam had my low pressure. Put a can of 134r in, was still low but worked pretty good any way. And compressor functioned properly after that.
You can take it in if you want. I'd expect any a/c professional to advise it. Easy money for them, but I live in WI and have to drive to another state to buy it. Maybe I'll try Ebay next year when it warms up. I'll check to see if its down or what it needs.

iceman2555 on Mon October 01, 2007 11:39 AM User is offlineView users profile

[You can take it in if you want. I'd expect any a/c professional to advise it. Easy money for them, but I live in WI and have to drive to another state to buy it. Maybe I'll try Ebay next year when it warms up. I'll check to see if its down or what it needs.



It is simply not the idea that it is easy money for a pro....in some cases it may be even more costly.....however, the modern A/C system that is operated with an undercharge of 10-15% can suffer severe compressor failures due to lack of lubricant flow. When the systems were 48 oz and above the 10% left a large margin for undercharging....however with the new system and recharge rates becoming less and less..... this Ford is requires 33 oz....more than two cans...less than three....equipment charges are much more reliable.....
Good luck!!!

-------------------------
The strongest reason for the people to retain the right to keep and bear arms is, as a last resort, to protect themselves against tyranny in government.
Thomas Jefferson

mk378 on Mon October 01, 2007 1:32 PM User is offline

Here is the problem with using a single gauge, note in the original post that the high side is 450 psi, so it is cycling on the high pressure switch. Someone with a single gauge wal-mart special wouldn't know that.

NickD on Tue October 02, 2007 7:45 AM User is offline

Quote
Easy money for them, but I live in WI and have to drive to another state to buy it.

WI was selling R-134a on a trial period, didn't keep track if that is still going on, but at seven bucks for a 12 oz can, 30 pound tanks were not available, purchased a 30# tank anyway, out of state for around 90 bucks, the same amount would have cost $280.00 in the cans. But what the heck, had to drive out of state to buy a box or margarine a few years back so use to it. Beer is cheap, plentiful, and sold at every gas station, but that is a trap, catch you with an open can of beer in your car and you are screwed to the wall.

Family has a 150 year history in this state, but many of my relatives are moving out, corruption in government and very high taxes, so why are we still here?

mikeal21 on Wed October 03, 2007 7:13 AM User is offline

Beer and cheese! The Pack is 4-0, who needs some whine to go with dat aah. Going to California with a aching in my heart. How does that song go Wine in the Jar, maybe not. But I'll still whining about driving 40 miles for a can of R134a, dam bureaucrats. It's hard to keep your A/C tuned up when its only running 3 months a year....

Edited: Wed October 03, 2007 at 7:14 AM by mikeal21

jed1154 on Mon October 29, 2007 3:59 PM User is offline

I dont think you can diagnose an ac problem by how much the AC compressor cycles. I have a 2005 Diesel F-250 and from when the clutch disengages to when it engages is 10-13 seconds. However, it seems to cool well.

NickD on Tue October 30, 2007 7:08 AM User is offline

450 PSI at 87*F is crazy, HPCO has got to be doing that cycling, wouldn't expect much more than 250 PSI. Was this system worked on before to get these high pressures? Was R-134a with a hard sealant added that could be plugging up the orifice? Of is the system original with a condenser plugged up with WI bugs?

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