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
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Hi Larry
There is another section of the forum devoted to heating and cooling. Some really sharp guys hang out there and I bet one would be glad to help you. If they don't get you going, come on back. Well, come on back anyway.
Good Luck Frank
https://www.ford-trucks.com/forums/forum61/
There is another section of the forum devoted to heating and cooling. Some really sharp guys hang out there and I bet one would be glad to help you. If they don't get you going, come on back. Well, come on back anyway.
Good Luck Frank
https://www.ford-trucks.com/forums/forum61/
Fleet Owner
Joined: Aug 2005
Posts: 23,668
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From: Easton,Ks
Not sure what you mean by "I tried bumping the hub plate while the engine is running and the coil energized with no success".
The damper diode is to stop the ringing from the A/C coil.
Sounds like you do not have a good ground in the A/C circuit.
Here is a diagram of your system:
http://i54.photobucket.com/albums/g9...stem/PG118.jpg
The damper diode is to stop the ringing from the A/C coil.
Sounds like you do not have a good ground in the A/C circuit.
Here is a diagram of your system:
http://i54.photobucket.com/albums/g9...stem/PG118.jpg
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[Not sure what you mean by "I tried bumping the hub plate while the engine is running and the coil energized with no success".]
The troubleshooting chart supplied with the coil suggested to try to engage the hub by gently pushing against it with a wooden rod. This was to be done with the engine running and the ac switch on. If bumping the hub plate engaged the copressor, then the air gap is too wide or the coil draw is insufficient.
I hope I explained this properly.
The troubleshooting chart supplied with the coil suggested to try to engage the hub by gently pushing against it with a wooden rod. This was to be done with the engine running and the ac switch on. If bumping the hub plate engaged the copressor, then the air gap is too wide or the coil draw is insufficient.
I hope I explained this properly.
Fleet Owner
Joined: Aug 2005
Posts: 23,668
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From: Easton,Ks
Originally Posted by barnetto
[Not sure what you mean by "I tried bumping the hub plate while the engine is running and the coil energized with no success".]
The troubleshooting chart supplied with the coil suggested to try to engage the hub by gently pushing against it with a wooden rod. This was to be done with the engine running and the ac switch on. If bumping the hub plate engaged the copressor, then the air gap is too wide or the coil draw is insufficient.
I hope I explained this properly.
The troubleshooting chart supplied with the coil suggested to try to engage the hub by gently pushing against it with a wooden rod. This was to be done with the engine running and the ac switch on. If bumping the hub plate engaged the copressor, then the air gap is too wide or the coil draw is insufficient.
I hope I explained this properly.
Posting Guru
Joined: Jan 2002
Posts: 1,346
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From: Baltimore
Here's the schematic posted by Subford.
If you have 12 volts at one end of the coil, to complete the circuit you need a ground on the other end of the coil, (Black wire).
Disconnect the plug and measure the resistance on the end of the plug Black wire to the negative of the battery terminal. Should be close to zero.
If you have 12 volts at one end of the coil, to complete the circuit you need a ground on the other end of the coil, (Black wire).
Disconnect the plug and measure the resistance on the end of the plug Black wire to the negative of the battery terminal. Should be close to zero.
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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
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