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Discussion Starter #1
Forgive my ignorance, my knowledge of AC systems is nothing. This year I went to turn on air conditioning and the air blew warm. Seemed to work fine last year. Noticed the compressor never kicks on at any time. Light on the button lights up, but no audible noise to kick on.

Is this as simple as low refrigerant? What should the pressure be? If any one can give me a few things to check and rule out that would be very helpful.
 

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Check the fuse first.

If not, then probably low on refrigerant as you suspect. A reputable local A/C should should be able to get you all set up. However, if you are low on refrigerant, that means you have a leak. You may get by with having them top it off for you only to find it leaks out - at which time you'll need to have them perform a leak detection then replace seals.

The only other thing I can personally think that causes A/C not to work is engine temperature too high. That could be a faulty temperature sensor, but I think you'd have other reasons to think the temperature sensor was faulty.
 

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have a performance check done at your local shop that does reputable ac work . check for leaks with a dye test, could be low on refrigerant or pag oil. check the connection that plugs into the ac pump itself. the fuse rarely blows out. but check that and the relay. that powers it.
 

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From memory, the circuit to control on/off of the compressor:

The fuse
The AC switch on the dash
the temperature-sensor for interior temperature
the refrigerant pressure-sensor (to detect refrigerant pressure too low or too high)
the relays <---------------------------------------------- edited to add
the BCM

The BCM decides when to switch the compressor on or off based on all the things in that list. This is pretty typical of the AC system on all vehicles these days.

The refrigerant pressure is too low when there is a leak resulting in not enough refrigerant present in the system.
The refrigerant pressure is too high when the compressor is pushing the fluid (refrigerant) harder than the condenser is able to cool and condense it.

Programmed into the BCM is an upper pressure limit and a lower pressure limit.
The actual pressure moment-to-moment must be somewhere between the lower and the upper limits (as measured by that single pressure sensor), else the PCM will not energize the clutch-
..even when it needs to do so to cool the interior.


Other than the sensors and electronics, it's all a matter of the basic physics involved (AC theory).
 

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Ron Lopes
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I would also rec. giving a tap on the front of the compressor with a wooden handle of a hammer.(while a/c on max) Clutch clearance can become sticky, make sure the compressor can be turned by hand. (engine OFF) beyond that, like everyone said you need to have the charge level checked out.

DO NOT use a self recharge kit from autoparts stores.
 

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Discussion Starter #6
Is there a way to directly power the compressor and bypass everything in this system to make sure it engages?
 

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Check the 15A IGN Fuse (#23) and the 10A A/C COMP fuse (#77)

Also check the A/C COMP Relay (#50) as well as the A/C Clutch Diode (#65).

There are two wires that feed the A/C Compressor clutch, The dark-green is positive and the black is a ground. You should be able to engage the clutch with a PowerProbe III or similar.
 

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You can pull the compressor relay and use a jumper from the battery to the receptacle for the output lead of the relay. Not sure if it is pin 30 or 78. Pin ID is on the bottom of the relay. Don't jam a large object in the relay receptacle as it will stretch it and cause more problems. This would be without the engine running, to check to see if the clutch will "click".

If you can find a set of gages, check the static pressure (system not operating). For ambient temps above 60° the pressure should be at least 50psi. Above 75° it should be 70psi. Both high and low gages should be within 15psi of each other. If the pressure is less that 44psi, the compressor clutch will not engage.
 

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Ron Lopes
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Swap the a/c relay with another known good one, if it clicks you're getting the request, you wont get the request with under or over charged though.

To verify ckt integrity i suggest then jumping the contact pins from the relay (powering ckt 59 via the relay pin) and make sure the clutch engages (or use a headlamp bulb in the connector) to load test it.

If the a/c relay clicks and the ckt checks ok you have a failed compressor

If the relay doesn't click your easiest least intrusive step is to have charge checked.

Beyond that, I'd need the operation of the pressure switch for this system to see if you could jump it ( I jump fords older fords that way sometimes when I am waiting for the a/c machine at work)
 

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Discussion Starter #11
Thanks for all the replies. Ended being a connector popped out from behind the dash due to me replacing the blower motor harness last fall.
 

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Thanks for all the replies. Ended being a connector popped out from behind the dash due to me replacing the blower motor harness last fall.
Which connector was it? Mine is doing the same yours was. I do know that my brown wire (blower speed 4) is broken at the connector behind the glove box. I plan on jumping that connector.
 

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Thanks for all the replies. Ended being a connector popped out from behind the dash due to me replacing the blower motor harness last fall.
Thanks for posting your findings for the benefit of others facing this problem.
 

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The signal from the HVAC Control Module to the BCM goes through connector C203. Dark Green wire with White stripe. C203 can be accessed by dropping the glove box door and looking straight forward. It is a 14 pin connector clipped the the face of the HVAC case. The circuit, same wire color code, also goes through connector C201, located behind the right kick panel.
 

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I cut the brown wires from the connector (c203) behind the glove box and butted them together. Still no speed 4 on the blower, just 1-3.

If I cut and splice the green/white wire, would the AC come back on?
 

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In that connector (C203) the Orange wire is for the Blower high speed. If you jump that wire to ground, with the key on, the blower should operate on high speed.

Cutting and splicing the wires in the C203 connector would only be recommended if there was a problem in the connector, such as corrosion, burned terminals, etc. Have you determined that there is, in fact, a problem with the connector?

You could have a problem internally with the HVAC Control Module, if three of the blower speeds are normal, but high speed is inop.
 

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In that connector (C203) the Orange wire is for the Blower high speed. If you jump that wire to ground, with the key on, the blower should operate on high speed.

Cutting and splicing the wires in the C203 connector would only be recommended if there was a problem in the connector, such as corrosion, burned terminals, etc. Have you determined that there is, in fact, a problem with the connector?

You could have a problem internally with the HVAC Control Module, if three of the blower speeds are normal, but high speed is inop.
My fan had been cutting out on all speeds. I would open the glove box and squeeze that connector, and it would come back on. It progressed to the point that I would have to really work the wires on both ends of the connector to get it to work. Then finally I could feel something snap. I just figured it was the tan wire. When I cut it from the connector, none of the speeds (1-3) went away, so I figured that was in fact speed 4. But when I butt connected the tans back together, still no speed 4. So you're saying the orange wire is speed 4, what is the tan wire?
 

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The Tan wire would be the speed 2 control circuit.
Hmm. Okay, so I'll try the orange wire to fix the Speed 4 issue, and check the green for the AC.

That connector was made from a cheap nylon, and was prone to overheating. I know several have replaced with one from a Tacoma, and some have just butt-connected all of these wires and done away with the c203.
 

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The procedure that I suggested in Post #16 (Jump Orange wire to ground) will not "fix" your problem. If the blower works on high speed, when you connect the Orange wire to a good ground, that means the problem is in the circuit before the connector. What you would be doing, in effect, is bypassing the switch in the HVAC Module. The Orange wire goes to the blower switch in the HVAC module which should be connecting the circuit to ground when high speed is selected.
 
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