No Power to AC Compressor
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No Power to AC Compressor
Just installed a new AC compressor and recently took off my dash to get to the HVAC plenum. I reinstalled the compressor and went to recharge the system but I don't think I'm getting power to the compressor. I checked for 12v across the two leads on the plug that goes to the compressor and I got nothing. Possibly related, my fan blower motor will only run on high. I replaced the blower motor transistor and that did not fix the problem. I have a feeling I missed a connection when I removed the dash. If someone has a wiring diagram, knows where there is a connector that would be removed while removing the dash and the HVAC plenum, or if there is a fuse that runs both of these I'd love to hear about it. Thanks.
2008 F250 5.4L
2008 F250 5.4L
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Joined: Oct 2006
Posts: 10,167
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From: Texas
Just installed a new AC compressor and recently took off my dash to get to the HVAC plenum. I reinstalled the compressor and went to recharge the system but I don't think I'm getting power to the compressor. I checked for 12v across the two leads on the plug that goes to the compressor and I got nothing. Possibly related, my fan blower motor will only run on high. I replaced the blower motor transistor and that did not fix the problem. I have a feeling I missed a connection when I removed the dash. If someone has a wiring diagram, knows where there is a connector that would be removed while removing the dash and the HVAC plenum, or if there is a fuse that runs both of these I'd love to hear about it. Thanks.
2008 F250 5.4L
2008 F250 5.4L
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Interesting. With no refrigerant in the system, how do you get it to a high enough pressure to charge the AC? Used an external compressor to push it in? I thought you put it to the low side of the system and the system compressor is supposed to charge it?
Hotshot
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From: Texas
PS. It is to protect the compressor if there is no refrigerant in the system. No burning it up that way.
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From: St Louis
*** 99150 alluded... If you properly vacuumed the system, that first pound or so will practically jump in there and the static pressure from that partial charge is more than enough to satisfy the low pressure switch.
That said, it isn't as simple as suggested. This is a PCM-controlled system that uses a combination of a computer network, pressure-sensing switches, and relays etc to control the compressor clutch. Miss one detail and the whole thing just sits there doing nothing.
Need to know if you have the manual or automatic climate control.
That said, it isn't as simple as suggested. This is a PCM-controlled system that uses a combination of a computer network, pressure-sensing switches, and relays etc to control the compressor clutch. Miss one detail and the whole thing just sits there doing nothing.
Possibly related, my fan blower motor will only run on high. I replaced the blower motor transistor and that did not fix the problem.
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Good to know. I pulled about 20 in of vacuum before attempting to charge. I am charging from an old SnapOn recycling machine. The refrigerant has been in there since last fall and perhaps slowly leaked out. I should check the tare weight on the bottle.
The system is a manual system with single zone climate control.
The system is a manual system with single zone climate control.
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Update: 70 lbs both high and low side. In case that wasn't enough, I jumpered the low pressure switch and still got 0V at the plug into the compressor and the clutch will not kick on.
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Hotshot
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From: St Louis
You don't have an issue with the low pressure switch or the initial charge so that means the issue of clutch non-engagement is elsewhere.
On a manual climate control system, the high-only blower issue is virtually guaranteed to be an issue with the blower resistor. It might be the connector, harness or remotely possible, the EMTC module. I cannot find any connector which, if left unconnected, might account for the simultaneous blower circuit fault and the lack of clutch engagement. I would approach them as separate faults.
Do you have a scan tool or comparable capable of reading PIDs from the PCM and other modules?
On a manual climate control system, the high-only blower issue is virtually guaranteed to be an issue with the blower resistor. It might be the connector, harness or remotely possible, the EMTC module. I cannot find any connector which, if left unconnected, might account for the simultaneous blower circuit fault and the lack of clutch engagement. I would approach them as separate faults.
Do you have a scan tool or comparable capable of reading PIDs from the PCM and other modules?
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Hotshot
Joined: Oct 2006
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From: Texas
You don't have an issue with the low pressure switch or the initial charge so that means the issue of clutch non-engagement is elsewhere.
On a manual climate control system, the high-only blower issue is virtually guaranteed to be an issue with the blower resistor. It might be the connector, harness or remotely possible, the EMTC module. I cannot find any connector which, if left unconnected, might account for the simultaneous blower circuit fault and the lack of clutch engagement. I would approach them as separate faults.
Do you have a scan tool or comparable capable of reading PIDs from the PCM and other modules?
On a manual climate control system, the high-only blower issue is virtually guaranteed to be an issue with the blower resistor. It might be the connector, harness or remotely possible, the EMTC module. I cannot find any connector which, if left unconnected, might account for the simultaneous blower circuit fault and the lack of clutch engagement. I would approach them as separate faults.
Do you have a scan tool or comparable capable of reading PIDs from the PCM and other modules?
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You're supposed to pull 30 in. of vacuum and then make sure it holds for 10-minutes before charging the system. If you didn't do that you could have a leak and will lose all the refrigerant you put in there.
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