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go-west.., Technician
Category: Medium and Heavy Trucks
Satisfied Customers: 1178
Experience:  Technican with 20 years experience focused on engines and electrical.
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Ac compressor won't come on, 2004 Freightliner Columbia,

Customer Question

Ac compressor won't come on
JA: What's the make/model/year of your truck? Engine type?
Customer: 2004 Freightliner Columbia
JA: Are you fixing your truck yourself? What have you tried so far?
Customer: Hard wired compressor, it comes on when I do that
JA: Anything else you want the truck mechanic to know before I connect you?
Customer: The blower motor won't come on unless I pull the fuse and put it back in
Submitted: 10 days ago.
Category: Medium and Heavy Trucks
Expert:  go-west.. replied 10 days ago.

Good evening

the power flow to the a.c. compressor is pretty easy to flow, comes from the a/c relay to the binary switch from there to the compressor,the binary switch is at the receiver dryer,unplug the sender that has wire 97 t going to it,if there is power there ,jump the sender and see if the compressor kicks it,if it does check for a low charge and if the charge is ok then the switch could be faulty,Let me know how you do.

Customer: replied 10 days ago.
I jumped the switch (did not check power), didn't kick on. 95 psi at port
Customer: replied 10 days ago.
I'll check power at switch tomorrow
Expert:  go-west.. replied 10 days ago.

if no power

go to the panel infront of the passengers legs,remove and inbehind the panel to the upper left side there is the themostatic switch,unplug there and there should be power there at one side of the switch,Let me know how you do.

Customer: replied 9 days ago.
No power here (see pic)
Customer: replied 9 days ago.
Is the thermostatic switch labeled?
Customer: replied 9 days ago.
The hvac 20amp relay/fuse is blown
Customer: replied 9 days ago.
The compressir will stay on for 15 seconds if I pull both mini fuses and reinsert. Of course it shuts off. No power to the switch near the dryer
Expert:  go-west.. replied 9 days ago.

nice picks

what happened after the mega fuse is replaced,did it blow again ?

this what the thermostatic switch looks like if you truck has it,your vintage of truck is on the brink of the change an some trucks (older don't have it..)

sorry for the delay on the answer..

Customer: replied 9 days ago.
I have not seen that switch. It didn't blow the fuse again. Pulling the mini fuses for the blower more and reinserting them will now start the compressor for 15 seconds. No power to the pressure switch. Don't know what else to do, it's scheduled for the dealership in the morning
Expert:  go-west.. replied 9 days ago.


go to page 10 of this link at have a read,im thing the clutch resistance is out of range and causing the clutch to kick out.,slap a ohm meter on the clutch and please tell me the resistance

Customer: replied 9 days ago.
I don't know where the ac clutchi relay is, or pin 87 or pin 30. Sorry, this is really my first time working on a truck of this size
Expert:  go-west.. replied 9 days ago.

oh ok

unplug the a.c compressor clutch and tell me the resistance,set meter to a 200 ohm range,if meter is auto range at is ok to.

Customer: replied 9 days ago.
Everything off, resistance between the two wires coming out of the clutch went to 0.00
Customer: replied 9 days ago.
I got out of bed for this...
Customer: replied 9 days ago.
Customer: replied 9 days ago.
Don't worry about it I have to get up in 3 hours
Expert:  go-west.. replied 9 days ago.
Sounds like the clutch is shorted,

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