fading A/C
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fading A/C
I have a '92 E 250 with a 5.8 litre eng. just latley when I turn on the A/C while sitting still, the A/C will come out the dash vents. As soon as I get into the throttle though the A/C fades out and appears to be coming out the defroster. I have been over the vacuum lines in this truck extensivley and can't find a vacuum leak. I suspect a valve in the A/C system. There is a vac line running from the Intake manifold to the A/C housing. When I disconnect this line the engine rpm's rise. I put a vacuum guage on the engine and it's just below the green band. also when i drive the truck about 25-35 mph i get a sort of bump like a miss. but I know the ingnition is OK. I also put my snap-on computer on the truck and it has no codes and passes the eoer test. any ideas? I could use a little help. I have an e4od extreme duty trans, Accel ignition coil and wires, Bosch quad platinum plugs, shorty headers,Flowmaster exhaust, K&N air filter and a super chips performance chip installed. I want to build this motor some more but this driveabailty problem is annoying me. Thanks in advance
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Joined: Jan 2001
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From: Nebraska
Originally posted by goofy173
Nope. Still a vacuum leak.
If you want performance, then remove the A/C compressor. Why let it steal power?
Nope. Still a vacuum leak.
If you want performance, then remove the A/C compressor. Why let it steal power?
Lead Driver
Joined: Feb 2000
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From: Palm Bay, Florida
The most probable place to check is the milky white colored vacuum line coming from the firewall wireing on the right side of the engine compartment going to the vacuum solinoyd for the a/c system, these lines deteriorate with time and temperature, you can patch in a new section of line by using a 1/8" black line available at most chain type parts stores, and a 1/8" coupler at both ends, you will want to strip back the tape on the wireing bundle at least an inch to get some fresh white line to graft onto to start with, this has been the problem most of the time with the '92-'96 Fseries, cheap fix too!!!
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i have a 95 f150 that was doing the same thing when i got on it the ac stopped coming out the vents and started coming out the defrost vent up by the windsheild. under the hood on the left side of the engine looking in there is a red vacume line that goes into a tee with two black lines coming out that tee is a oneway checkvalve mine was bad i had to replace it it only cost like 9 dollars i think at the ford dealership hope it helps
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Joined: Sep 2003
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From: Farmington, MN
Originally posted by brown 4x4
When the a/c is off, the clutch is disengaged and the pulley on the compressor freewheels. That uses nearly zero horsepower to turn.
When the a/c is off, the clutch is disengaged and the pulley on the compressor freewheels. That uses nearly zero horsepower to turn.
BUT
as just about anyone who has done any drag racing can tell you, an idler pully can steal 2-4 HP from an engine easily
T
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thanks for all the input. as it turned out the problem was in the blower box, or to be more accurate in the blower box assembly. it seems the vacuum hose that supplies the vac to operate the venting systemruns ( looking at the truck from under the hood) down the left side of the engine compartment behind the AC unit and emerges in the cabin through the blower box housing( although not through the blower area) in the cab. I tested the vac at the connection under the hood and had engine vacuum. in the cab i had about 10%. when we tried to access the connection we pulled the grommet out of the blower box face and the vac connection came out without a tug. apparently the connection was bareley together. OK I could not reach the connection behind the AC unit because of the close fit. what we did was run a sepearte line to the vac feed bypassing the original connection and all is well in AC land again. Hope this helps someone else, darn near broke my forearm reaching around that AC unit. Thanks again to all who pined in on this YOU WERE RIGHT...a vacuum leak!!
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