A/C compressor cycling A LOT
Thread Starter
|
Elder User
Joined: Mar 2005
Posts: 905
Likes: 0
A/C compressor cycling A LOT
At idle, if i have my lights on, fan on high and radio on not very loud and I turn the A/C on, I hear the compressor click on and rpms decrease, then a moment later the rpms rise again. 5 seconds later, the rpms go down again for a moment then go up again. It's almost like the compressor doesn't have enough charge or something. Here's a twist though. If I turn the fan down, and try again, the a/c will work. Another twist, if i ramp up the engine even just 3-400 rpms, the a/c compressor clicks on and stays on. Is this normal?? A bit odd...
Posting Guru
Joined: Jun 2004
Posts: 1,635
Likes: 0
From: Niceville, FL.
My theory is that with the engine speed very low and current draw from the alternator high (thus the engine load due to the both the A/C compressor and alternator is also high for its idle speed) the computer is telling the air conditioning clutch to shut off. Shutting off the A/C reduces load on engine so its speed increases. As speed increases, computer senses increase and allows A/C to come back on. Cycle begins again. Once you manually increase engine speed a slight amount there is enough of both mechanical power and electrical power available for normal operation. Possibly your idle speed is somehow set too low.
Last edited by Piffery1; Jul 12, 2006 at 02:09 AM.
Posting Guru
Joined: Jun 2004
Posts: 1,635
Likes: 0
From: Niceville, FL.
I thought about low refrigerant but, if it was low the cycling rate should increase with engine speed not decrease. I.e., the faster the compressor turns, the faster the suction pressure drops, thus the shorter the cycle time interval.
Posting Guru
Joined: Apr 2003
Posts: 1,045
Likes: 1
Originally Posted by mymechanic'sanidiot
I had a similar problem with mine a few weeks ago. Turned out I had almost no refrigerant in my a/c system. Had it checked for leaks and there were none. So far its running great.
Posting Guru
Joined: Jun 2004
Posts: 1,635
Likes: 0
From: Niceville, FL.
Or, maybe the battery has weakened to the point that alternator has to provide almost all the current at idle speed. Do the lights get significantly brighter as the speed is increased above idle? Is idle rpm within specs?
Trending Topics
Thread Starter
|
Elder User
Joined: Mar 2005
Posts: 905
Likes: 0
FTE Stories
Ford Trucks for Ford Truck Enthusiasts
Rezvani's Latest Post-Apocalytic Monster Is a Ford F-150 Raptor Underneath
Verdad Gallardo
Top 10 Most Expensive Ford Trucks Ever Sold on Bring a Trailer
Joe Kucinski
2027 Ford Super Duty Buyer's Guide (Every Model, Engine, & Package)
Brett Foote
Top 10 Ford Truck Tragedies
Joe Kucinski
AEV FXL Super Duty - the Super Duty Raptor Ford Doesn't Make
Brett Foote
Lobo Vs Lobo: Proof the F-150 Lobo Should Be Even Lower!
Michael S. Palmer
Ford's 2001 Explorer Sportsman Concept Looks For a New Home
Verdad Gallardo
10 Best Ford Truck Engines We Miss the Most!
Joe Kucinski
2026 Shelby F-150 Off-Road: Better Than a Raptor R?
Brett Foote
Elder User
Joined: Nov 2004
Posts: 759
Likes: 0
From: Ventura ,ca. (near L.A.)
My freinds 03' Tremor does the same exact thing, it's driving us nuts. The theory about the Alternator is not true since the Trmor came factory with a 120 amp alternator. I checked the charged with the problem gauge, and i also hot wired both the low pressure and high pressure cycle switches and it still did it's rapid cycle crap. My truck is an 02' and since it's a manual trans there is no load from the trans holding the engine back which is why it doesn't do it. Cranking up the idle a little could work, somebody else told my it could be the throttle position sensor but my freind is reluctant the start throwing money at his truck buying things it might not need.
Posting Guru
Joined: Jun 2004
Posts: 1,635
Likes: 0
From: Niceville, FL.
Since you've bypassed both pressure switches and checked the refrigerant charge then the "Wide Open A/C Cutoff Relay" activated by the "Powertrain Control Module" (PCM) must be what's causing the rapid cycling. I think there are probably a number of functions that are input to the PCM that could cause it to tell this relay to "open" the clutch circuit among them being: "A/C Off", wide open throttle position, temperature too high, idle speed too low, battery voltage too low, etc., etc. If this is the case, you might look for stored trouble codes for a clue; not all codes cause a "Check Engine Light", and some may reset automatically if they don't last for a prescribed period of time. My guess is that you may have to resort to having a well equipped shop use some really good diagnostic/recording equipment to find the cause.
Thread
Thread Starter
Forum
Replies
Last Post
chrislambing
1999 - 2016 Super Duty
7
Mar 14, 2015 03:53 PM
jtharvey
1999 - 2003 7.3L Power Stroke Diesel
9
Aug 4, 2008 09:50 AM