I have been searching for this problem, and I located only one result from June 2014. The poster had the same problem I am having but never posted a solution. I hope someone can help me with this.

This is in a 2004 Explorer
The A/C will not engage until the engine is warm (at or above 175 degrees)
What I know

• The refrigerant charge is correct
• once the engine is warm and the A/C kicks on, the high and low-pressure side are within acceptable pressures
• the electric radiator fan and A/C clutch both engage and disengage together.
• The low-pressure switch is good
• The high-pressure switch is good and is reporting proper high-pressure side readings to the computer as verified with mechanical gauges
• the A/C relay is working
• the throttle position sensor is good
• the engine temp sensor, gauge on the dash, and actual coolant temp, as verified with a thermometer, are all within a few degrees of each other.
• Once the engine comes to or above 185 degrees, the A/C works as expected and blows cold.
• With my computer hooked up - before the engine is warm, I can see the PCM is calling for the A/C compressor to be switched on but neither the A/C clutch nor the electric radiator fan engage. Once the engine is above 185 degrees, the A/C compressor and radiator fan engage and disengage as expected and in agreement with what the computer is reporting.

Is there something I am missing? I am normally very good at diagnosing these kinds of problems, but this one has me stumped!

 

Have you checked the clutch gap?

 

Simple hack is to tap the frt. of the clutch with the wood handle of a hammer while it's all on. If it engages the gap is probably too big and or the clutch is too weak to pull the clutch plate in to engage it. If the gap is over about .014 remove the bolt in the frt. and pull the clutch plate. There is a washer or washers in there that shim the plate to adjust the gap. Remove washers or find a thinner washer to get the gap tighter.

 

Thanks for the tip, but this is not a clutch or compressor issue. The A/C is not getting power until the engine temp reaches 175-185 degrees. I wonder if it could be the cabin temperature sensor. If the cabin temperature sensor is reporting that it is very cold in the cabin, it may delay the A/C start until the heater core is warm enough to warm the air before pumping it into the cabin. I don't know what else it could be. I have checked every component of the system from the control head, to the post evaporator temperature sensor, to the high and low pressure sensors. The whole system is powered off until the engine temp rises. The only thing I can think of is the computer is trying not to allow the A/C to pump cold air into an already very cold cabin.

Any thoughts?

 

There is no cabin temperature sensor on an 04 Ranger. It's a fairly simple (hah!) PCM-controlled clutch system. The only inputs to the PCM are:

1) The mode switch (+12V in all positions except OFF, VENT, and FLOOR) via CJB F27. A/C Demand signal.

2) The series circuit of the low and high pressure switches. Should be a ground signal when both are valid. If wither switch is open, should be +12V.

What specific PIDs are you monitoring with your computer?

 

Geeze... I was confused by your post when you said a "Ranger" doesn't have a temperature sensor. I went back and looked at my original post and I did indeed type "Ranger". My mistake and I am sure it led to some confusion. I edited the original post to read Explorer.

I have a digital climate control panel so I assume there must be a temperature sensor behind the little grill in the dash board. My computer dose not show a monitor for that sensor, so I don't have any idea what it is reporting to the PCM.

I am monitoring ECT, A/C Pressure Sensor (psi), A/C Low Pressure Switch, A/C Clutch, A/C Pressure Sensor Voltage, Cylinder Head Temp Cold Value and Hot Value, Post Evap Temp Sensor and Ambient Temp Sensor. My computer does not show a cabin air temp sensor, so I don't know what that is doing.

 

Yeah, being an Explorer with EATC changes everything.

The EATC has an input for the cabin air temp.sensor. you'd have to pull up the PID for that through the EATC which means your software in use has to support that function.

 

So I did a software updated and downloaded the module so I can see the EATC. Everything was reporting normal until I began to fiddle with stuff. What I discovered was by testing method was flawed in the beginning - leading me down the wrong path.

With the scan tool reading the EATC and PCM, I discovered when I removed the A/C power relay, the whole A/C circuit went into error. So when I tried to test the trigger wire for the relay, I got nothing, making me think the problem was in the PCM or EATC. Once I saw the system was going into error, I pulled out my relay / circuit tester and found a working but weak relay. When the relay latched, the A/C worked, but the relay would not latch until it was under power for about 5 minutes. I have not run into a relay that did that before - I am guessing the thermal change inside the relay eventually caused it to latch?

The bottom line is, I have been out of the business (professionally) for almost 25 years - and while I am confident I can still diagnose and repair just about anything, it is clear I am out of practice. LOL

Thank you for your help -

Bottom line is, after hours of fiddling around with this thing, had I just done the old school "swap a known good relay" trick to begin with, I would have had it fixed in 10 minutes and I would not have had to download a software module for a 20 year old car that I will probably never use again. LOL

Thanks again!

 

Kudos to you for sticking with it and finding a bad relay. Hope I remember that trick for later. Especially difficult to find a weak relay. Well done!