AC help

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trentehrlish

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MY ac has started to not work anymore. So i have the schematics for it but need more help. The compressor will not engage. It has normal refrigerant levels. I don't get any volts at the compressor even with the low and high pressure switches jumped with a paper clip. What could it be?When i just have the low pressure switch jumped, i get normal volts at the high pressure switch but nothing still at the compressor.
 

dudeman2009

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First, put everything back to normal, pressure switches rarely go bad.

You need to unplug and measure the connector on the A/C compressor clutch. It should be a dark blue/black wire. The engine must be running with max A/C selected. If you are reading 0V, pull the low side pressure switch and jump the brown wire to ground. If the compressor does engage, plug the sensor back in and jump the dark blue wire from the high side switch to ground. If the compressor doesn't work, check the low side switch and wiring for continuity. If it does work, check the high side switch for continuity, if it checks good, check the light green/white wire for continuity to ground. If it doesn't check out, the wire is damaged between there and the A/C select switch.

If everything has checked out so far move to the underhood PDC.

Look for the A/C compressor clutch relay. pull it and probe pin 30 on the PDC, you should read battery voltage. If you didn't, replace fuse J in the PDC. If you did read battery voltage, probe pin 86, if there is no voltage, replace fuse 11 in the cabin junction block. If there is battery voltage on pin 86, switch to resistance and probe from ground to pin 85, you should read near 0 ohms. If you read near 0 ohms, swap the relay for a known good relay. If the known good relay clicks, probe for resistance from pin 87 to the dark blue/black wire on the compressor clutch, you should read near 0 ohms. If not, the wire is damaged and needs to be replaced.

If everything has checked out so far, use a fused jumper wire to jump the A/C compressor clutch to battery positive, if it fails to engage, replace the clutch.
 
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trentehrlish

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Thanks for your time. I will try this once i get back home from college in a couple days. I will let you know how it goes.
First, put everything back to normal, pressure switches rarely go bad.

You need to unplug and measure the connector on the A/C compressor clutch. It should be a dark blue/black wire. The engine must be running with max A/C selected. If you are reading 0V, pull the low side pressure switch and jump the brown wire to ground. If the compressor does engage, plug the sensor back in and jump the dark blue wire from the high side switch to ground. If the compressor doesn't work, check the low side switch and wiring for continuity. If it does work, check the high side switch for continuity, if it checks good, check the light green/white wire for continuity to ground. If it doesn't check out, the wire is damaged between there and the A/C select switch.

If everything has checked out so far move to the underhood PDC.

Look for the A/C compressor clutch relay. pull it and probe pin 30 on the PDC, you should read battery voltage. If you didn't, replace fuse J in the PDC. If you did read battery voltage, probe pin 86, if there is no voltage, replace fuse 11 in the cabin junction block. If there is battery voltage on pin 86, switch to resistance and probe from ground to pin 85, you should read near 0 ohms. If you read near 0 ohms, swap the relay for a known good relay. If the known good relay clicks, probe for resistance from pin 87 to the dark blue/black wire on the compressor clutch, you should read near 0 ohms. If not, the wire is damaged and needs to be replaced.

If everything has checked out so far, use a fused jumper wire to jump the A/C compressor clutch to battery positive, if it fails to engage, replace the clutch.
 
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trentehrlish

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Help

I am still in college so I decided to just pull fuse 11 and see if it was blown. It was not so i put it back in and now i have a check engine light on. P0443 which is An open or shorted condition detected in the EVAP purge solenoid control circuit. What happened?
 

dudeman2009

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That fuse feeds multiple systems/ When you pulled the fuse, another system got mad, thats not uncommon. Just ignore that other code. The troubleshooting steps are listed above. If you get confused or stuck on one, let me know and i'll try to help explain it.
 
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trentehrlish

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That fuse feeds multiple systems/ When you pulled the fuse, another system got mad, thats not uncommon. Just ignore that other code. The troubleshooting steps are listed above. If you get confused or stuck on one, let me know and i'll try to help explain it.

But my check engine light wasn't on before and now it is. I don't want to just "ignore it"
 

dudeman2009

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But my check engine light wasn't on before and now it is. I don't want to just "ignore it"

When you pulled the fuse, you cut power to more than just the AC system. This can cause other systems in the truck to throw codes that are completely wrong. If the code showed up after you pulled the fuse and before you took it for a long drive, its probably nothing. Clear the code and see if it comes back. Thats all shops do for something as vague as a code like this. Clear it, drive it until its up to operating temp and see if it comes back.

Its the EVAP system anyway, all that does is control vehicle emissions, i've been running with a similar code about both a large and small EVAP system leak for the past 3 1/2 years.
 
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