1988 AC compressor coil problems?
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1988 AC compressor coil problems?
I am having AC problems on a 1988 F-150 with 302 and auto trans. The compressor coil will not pull the hub in to engage the compressor. I have ~13 volts at the coil connector. I bypassed the pressure switch, the system is charged, I bypassed the switch to rule that out as a problem. I checked the hub clearance, it is .030.
I purchased a new coil and hub assembly and installed it with a .030 air gap. The compressor will still not engage. I checked the resistance of both the old and new coils. It is at 3.0 to 3.5 ohms. I tried bumping the hub plate while the engine is running and the coil energized with no success.
I have noticed the coil harness appears to have a diode wired in. Could the problem be too little amperage to the coil? Any help will be appreciated.
Thank you,
Larry B
I purchased a new coil and hub assembly and installed it with a .030 air gap. The compressor will still not engage. I checked the resistance of both the old and new coils. It is at 3.0 to 3.5 ohms. I tried bumping the hub plate while the engine is running and the coil energized with no success.
I have noticed the coil harness appears to have a diode wired in. Could the problem be too little amperage to the coil? Any help will be appreciated.
Thank you,
Larry B
Fleet Mechanic
Joined: Feb 2006
Posts: 1,776
Likes: 5
From: Lorain County, Ohio
spelling correction
Originally Posted by barnetto
I am having AC problems on a 1988 F-150 with 302 and auto trans. The compressor coil will not pull the hub in to engage the compressor. I have ~13 volts at the coil connector. I bypassed the pressure switch, the system is charged, I bypassed the switch to rule that out as a problem. I checked the hub clearance, it is .030.
I purchased a new coil and hub assembly and installed it with a .030 air gap. The compressor will still not engage. I checked the resistance of both the old and new coils. It is at 3.0 to 3.5 ohms. I tried bumping the hub plate while the engine is running and the coil energized with no success.
I have noticed the coil harness appears to have a diode wired in. Could the problem be too little amperage to the coil? Any help will be appreciated.
Thank you,
Larry B
I purchased a new coil and hub assembly and installed it with a .030 air gap. The compressor will still not engage. I checked the resistance of both the old and new coils. It is at 3.0 to 3.5 ohms. I tried bumping the hub plate while the engine is running and the coil energized with no success.
I have noticed the coil harness appears to have a diode wired in. Could the problem be too little amperage to the coil? Any help will be appreciated.
Thank you,
Larry B
If your old coil measured 3.0 ohms, the original problem was also likely just the clutch gap. You could have adjusted it.
"I tried bumping the hub plate while the engine is running and the coil energized with no success." Did it engage or not, I don't understand this statement.
Tapping the clutch inward is the test for a wide gap. The magnetic field isn't enough to overcome the wide gap, but if you nudge it a bit, it will pull in and drive the compressor.
All of this is assuming a fully charged system and a good cycling switch.
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I was checking the ground and harness connections when I noticed the pressure switch wiring was loose inside the plastic connector. The wire had pulled loose from the metal crimp on the connector. When I jumped the switch yesterday, the connection was probably bad. I had voltage, but not enough current to energize the coil. I crimped a new connector for the pressure switch and now the coil pulls the hub in and operates the compressor.
Thank you for your advice.
Larry B
Thank you for your advice.
Larry B
Fleet Mechanic
Joined: Feb 2006
Posts: 1,776
Likes: 5
From: Lorain County, Ohio
Originally Posted by barnetto
I was checking the ground and harness connections when I noticed the pressure switch wiring was loose inside the plastic connector. The wire had pulled loose from the metal crimp on the connector. When I jumped the switch yesterday, the connection was probably bad. I had voltage, but not enough current to energize the coil. I crimped a new connector for the pressure switch and now the coil pulls the hub in and operates the compressor.
Thank you for your advice.
Larry B
Thank you for your advice.
Larry B
Back off that clutch gap, though. It may give you problems and it only takes 5 minutes on your truck.
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