A/C Compresser cycling switch
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A/C Compresser cycling switch
I have a 98 F150 s/c 4x4. My a/c has quit working. I've been told that it is the compressor cycling switch. I'm pretty sure of the location, but would like a picture/diagram of the switch and location to go by before I start working.
Any help is appreciated.
Eric
Any help is appreciated.
Eric
Fleet Mechanic
Joined: Feb 2006
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From: Lorain County, Ohio
Originally Posted by atomman1
I have a 98 F150 s/c 4x4. My a/c has quit working. I've been told that it is the compressor cycling switch. I'm pretty sure of the location, but would like a picture/diagram of the switch and location to go by before I start working.
Any help is appreciated.
Eric
Any help is appreciated.
Eric
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Well the switch didn't fix the problem. So I had my brother come down to help figure out what's going on. We used a jumper wire on the low pressure side to see if we'd gotten a bad part, the clutch did not kick in. We jumpered the compressor switch itself, no luck there either. We then tested to see if there was voltage getting to the compressor, there is voltage. Does that mean that the compressor is bad? Is there anything else I can check before giving up? Thanks for the help!
Fleet Mechanic
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From: Lorain County, Ohio
Did you make sure the other wire is grounded? The easy way is to put a test light across the connector terminals. If it lights, you're good.(Maybe you did it that way).
If you have power and ground to the compressor, try tapping the clutch face inward with the engine running and the AC on:
If the clutch pulls in, the clutch gap is too wide. It's adjustable by removing shims from the compressor shaft. Just remove the center bolt in the clutch and slide the clutch off. The shim(s) will be in the bore that indexes onto the sompressor shaft. (careful, they sometimes fall out when you remove the plate). You want .020" or less. A business card makes a good go/no go gauge.
If the clutch doesn't pull in, check the clutch coil resistance with an ohm meter. Should be 3-4 ohms. If it's not, you'll need to replace the clutch asy. It's about $100 and you don't need to open the system.
Hope this helps.
If you have power and ground to the compressor, try tapping the clutch face inward with the engine running and the AC on:
If the clutch pulls in, the clutch gap is too wide. It's adjustable by removing shims from the compressor shaft. Just remove the center bolt in the clutch and slide the clutch off. The shim(s) will be in the bore that indexes onto the sompressor shaft. (careful, they sometimes fall out when you remove the plate). You want .020" or less. A business card makes a good go/no go gauge.
If the clutch doesn't pull in, check the clutch coil resistance with an ohm meter. Should be 3-4 ohms. If it's not, you'll need to replace the clutch asy. It's about $100 and you don't need to open the system.
Hope this helps.
Fleet Mechanic
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From: Lorain County, Ohio
Originally Posted by atomman1
Thanks. We did use a test light to check for voltage. I'll try the clutch tapping tonight if I get time. Where would I check for the ohms? the compressor switch?
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Okay,
The tapping did not work and my fluke meter only read like 0.4-- something ohms. Obviously that's not right so it sounds like a clutch. Next question, how easy are these to rebuild? Can a shadetree guy like myself do it or should I take it to a tech? Thanks!
The tapping did not work and my fluke meter only read like 0.4-- something ohms. Obviously that's not right so it sounds like a clutch. Next question, how easy are these to rebuild? Can a shadetree guy like myself do it or should I take it to a tech? Thanks!
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Ford Parts Specialist
Joined: Nov 2006
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From: Simi Valley, CA
I don't have a parts catalog this late, but Ford for many years had a multi-ported "Air Conditioning Vacuum Selector Valve" that mounted to the levers on the heater/air conditioning panel behind the dash. The 'valve' is actually a vacuum manifold where the vacuum hoses attach. The valve also included the A/C kicker switch. When you move the lever to A/C, an audible click is heard = that's the A/C compressor kicking in.
Suggestion, before parting with the green, contact FTE sponsor DirectFordParts (Gaudin Ford in Las Vegas), and ask them if your truck has this part. The basic Ford part number is: 19B888. DirectFordParts link is on the home page, you may have to click on the refresh button a coupla times for it to appear.
Suggestion, before parting with the green, contact FTE sponsor DirectFordParts (Gaudin Ford in Las Vegas), and ask them if your truck has this part. The basic Ford part number is: 19B888. DirectFordParts link is on the home page, you may have to click on the refresh button a coupla times for it to appear.
Last edited by NumberDummy; Jul 5, 2007 at 07:21 AM.
Cargo Master
Joined: Dec 2006
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From: Central NY
also, if your AC charge is very low, the compressor won't kick on...that's what happened to my 2001.
refilled with a refill kit, supposedly only had a shrader valve leak on the low side, but now she's back to a 1.2 sec cycle rate, so there's a damn leak somewhere.
refilled with a refill kit, supposedly only had a shrader valve leak on the low side, but now she's back to a 1.2 sec cycle rate, so there's a damn leak somewhere.
Fleet Mechanic
Joined: Feb 2006
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From: Lorain County, Ohio
I'd say you found the problem. The clutch coil is open.
Replacing the clutch asy is easy.
-Remove the clutch center bolt and slide the clutch plate off.
- Remove the snap ring holding the pulley in place and slip the pulley and bearing off. (You may need to pry or tap it a bit).
- The coil is an interference fit, like a wheel seal. Pry or tap the coil off.
-Tap the new coil in place With a hammer and a block of wood. Make sure the connector is aligned with the notch in the compressor housing.
- Slide the new pulley on and reinstall the snap ring.
- Slip the clutch plate into place using the shims to set the clutch gap to .020 or less. The smaller the gap the better, as long as it doesn't rub the pulley.
- Install the center bolt. Use Loctite on the threads.
Replacing the clutch asy is easy.
-Remove the clutch center bolt and slide the clutch plate off.
- Remove the snap ring holding the pulley in place and slip the pulley and bearing off. (You may need to pry or tap it a bit).
- The coil is an interference fit, like a wheel seal. Pry or tap the coil off.
-Tap the new coil in place With a hammer and a block of wood. Make sure the connector is aligned with the notch in the compressor housing.
- Slide the new pulley on and reinstall the snap ring.
- Slip the clutch plate into place using the shims to set the clutch gap to .020 or less. The smaller the gap the better, as long as it doesn't rub the pulley.
- Install the center bolt. Use Loctite on the threads.
Hotshot
Joined: Jan 2004
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From: St Louis
I can see nothing in what he posted that would indicate the coil is open. I'd suspect a testing error as 0.4 ohms is not a valid reading of either a good coil or a bad coil except as noted below If that was the correct reading, then either the coil is shorted internally (rare) or the meter is defective. If the coil were, in fact shorted, other components will also be damaged from excessive current.
Steve
Steve
Last edited by projectSHO89; Jul 6, 2007 at 08:09 AM.
Fleet Mechanic
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From: Lorain County, Ohio
Originally Posted by projectSHO89
I can see nothing in what he posted that would indicate the coil is open. I'd suspect a testing error as 0.4 ohms is not a valid reading of either a good coil or a bad coil except as noted below If that was the correct reading, then either the coil is shorted internally (rare) or the meter is defective. If the coil were, in fact shorted, other components will also be damaged from excessive current.
Steve
Steve
- B+ and Ground to the clutch connector
- Lack of engagement when "bumping" the clutch plate.
I took the .4ohm reading as calibration error. My Fluke 73 will read .3-.4 on an open circuit if the meter isn't zeroed properly.
Fleet Mechanic
Joined: Feb 2006
Posts: 1,776
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From: Lorain County, Ohio
Originally Posted by projectSHO89
An OPEN circuit reads infinite, not less than 1 ohm.... That would be close to a SHORT circuit...
Steve
Steve
