A/C Diagnostic Help
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Tuned
Joined: Apr 2010
Posts: 280
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From: Tullahoma, TN
A/C Diagnostic Help
Hey guys,
I've searched the threads pretty decently for this answer before coming here, so I apologize if I've overlooked it...
I need help diagnosing why my A/C isn't working. I'm wondering if my clutch staying engaged has burned up my compressor before or after my clutch went bad. I don’t think it’s the air gap issue because I took my clutch off and checked and there were zero washers. I guess somehow I re-installed it with no washers maybe the last time I fooled with it.
I've only knew to check the air gap trick and when that didn't work, I wasn't sure what my next step could be. I tried looking at the high side pressure switch connector to see if it was burned up and it looked ok.
Could someone help me track down if my compressor is still good and replacing my clutch is the only thing I need to do or if I need to replace my compressor?
Or if there's something else that's totally unrelated that I need to check?
Thanks in advance.
I've searched the threads pretty decently for this answer before coming here, so I apologize if I've overlooked it...
I need help diagnosing why my A/C isn't working. I'm wondering if my clutch staying engaged has burned up my compressor before or after my clutch went bad. I don’t think it’s the air gap issue because I took my clutch off and checked and there were zero washers. I guess somehow I re-installed it with no washers maybe the last time I fooled with it.
I've only knew to check the air gap trick and when that didn't work, I wasn't sure what my next step could be. I tried looking at the high side pressure switch connector to see if it was burned up and it looked ok.
Could someone help me track down if my compressor is still good and replacing my clutch is the only thing I need to do or if I need to replace my compressor?
Or if there's something else that's totally unrelated that I need to check?
Thanks in advance.
Fleet Owner
Joined: Apr 2008
Posts: 24,316
Likes: 5,127
From: 0,0,1
Are you sure the clutch has been engaged 100% of the time? If the A/C system is turned to off does the compressor run or not?
There is no harm in the compressor running all the time unless the system is low on refrigerant. In such a case the low pressure/cycling switch was not able to shut down the compressor to prevent damage.
There is no harm in the compressor running all the time unless the system is low on refrigerant. In such a case the low pressure/cycling switch was not able to shut down the compressor to prevent damage.
Thread Starter
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Tuned
Joined: Apr 2010
Posts: 280
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From: Tullahoma, TN
I'm just assuming that at some point (maybe when I took out the last spacer out) it was too little clearance and the clutch down to nothing and now it won't engage, but I don't know for sure.
The only thing I do know for sure is that I can not get the clutch to engage at this time with zero spacers installed.
The only thing I do know for sure is that I can not get the clutch to engage at this time with zero spacers installed.
Fleet Owner
Joined: Apr 2008
Posts: 24,316
Likes: 5,127
From: 0,0,1
Have you tested the clutch coil for resistance or to see if it's getting 12 volts of power?
Thread Starter
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Tuned
Joined: Apr 2010
Posts: 280
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From: Tullahoma, TN
I have not - this is the type of things I was hoping to gain from you guys.
Could I get a quick explanation of how to test that?
Thread Starter
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Tuned
Joined: Apr 2010
Posts: 280
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From: Tullahoma, TN
1999 (post april build) - f250 super-duty (7.3L) - Manual climate controls
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Fleet Owner
Joined: Apr 2008
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From: 0,0,1
The easiest way is to access the A/C diode in the under hood fuse box. Run the A/C and test the voltage across the diode, it should be 12 volts. Then turn the truck off, remove the diode and take an ohm reading at the 2 terminals where the diode plugged in.
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Tuned
Joined: Apr 2010
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From: Tullahoma, TN
https://www.ford-trucks.com/forums/8...l-diagram.html
And I don't mean to be stupid, but what the trick to testing the diode with it installed? Can I get my multimeter leads in it or do I need to track the wires that come out the other side somewhere?
Thanks,
New User
Joined: Nov 2013
Posts: 9
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From: Texas
Ac clutch test
Have you tested the clutch to see if connecting 12 v to the compressor clutch ( you can check that w engine off unplug connector and apply power to comp leads )makes it engage ? If it does then check connector voltage with meter key on ac sw on also fuses and relays ( u can swap relay with a neighboring relay in box w/ same p/n , if it doesn't u may have bad coil on clutch if it engages but slips when running replace clutch I have seen some that were bent by someone trying to pry on it that slipped badly and removing and straightening it fixed slipping but it's always best to replace it if it's damaged or bad
Fleet Owner
Joined: Apr 2008
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From: 0,0,1
Forget it, sorry, I double checked and yours doesn't have it in the fuse box, it's in the harness, probably at the clutch connector.
So you'll have to take your readings at the clutch connector.
So you'll have to take your readings at the clutch connector.
Hotshot
Joined: Jan 2004
Posts: 19,760
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From: St Louis
To check coil continuity on this vehicle, disconnect the high pressure cutout switch, then measure resistance between the tan/light green wire of the connector and the vehicle ground. You should measure 3-6 ohms if the coil is good and that portion of the circuit is complete. Way easier than getting to some of the other components and this is a quick way of splitting the circuit in half.
Fleet Owner
Joined: Apr 2008
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From: 0,0,1
I thought of suggesting that but the diode shunts out the coil and gives a false reading, doesn't it?
Hotshot
Joined: Jan 2004
Posts: 19,760
Likes: 1,079
From: St Louis
Nope. The coil resistance is far, far less than that of a diode when it's forward biased.
Thread Starter
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Tuned
Joined: Apr 2010
Posts: 280
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From: Tullahoma, TN
To check coil continuity on this vehicle, disconnect the high pressure cutout switch, then measure resistance between the tan/light green wire of the connector and the vehicle ground. You should measure 3-6 ohms if the coil is good and that portion of the circuit is complete. Way easier than getting to some of the other components and this is a quick way of splitting the circuit in half.
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