pecanflyboy

I've read a lot about this issue, but can't figure it out.

2003 F150 SuperCrew 5.4L, 4X2
Air Conditioning worked perfectly last night. Nice and cold.

This morning, no worky. AC compressor clutch is not engaging.

Here is what I've done, engine running, Max AC, clutch will not engage compressor:

• Jumpered low pressure line switch
• Jumpered high pressure line switch
• Wiggled switch on compressor (could not get it to release, because I couldn't figure it out)
• Clutch will turn by hand, engine running and not
• Attempted to service low pressure port, but since the compressor was not running, the pressure at this port was 80+ PSI.
• Checked AC clutch relay, AC Fuse, and AC diode

Because it ran so well just 12 hours ago, I feel like it something electrical.

Any ideas?

Thanks,
Jimmy

papa tiger

You have AC pressure sensor and clutch sensor in line with each other, plus a ac diode and a AC clutch solenoid. Check your fuses ( 3 ) and test each component.

pecanflyboy

There are three fuses? I could only find one fuse, one relay, and one diode in the engine compartment fuse box. I checked there operation by exchanging with other working components. If there are more than I listed above, can you help me found them?

Thx
Jimmy

papa tiger

The manual shows #5, #22 or #24 and #105 as fuses for the system. There are 2 sensors one in the front /PSI cut off switch is on passenger side front of vehicle and rear fire wall, passenger side for AC cycling switch. The sol turns on the clutch. You really need a low cost VOM to trouble shoot the electrics. Look to make sure power is on both sides of the fuses and the sensors are working. PSI will toss the compressor. 80 PSI on the low side at what temp? Low side PSI at say 75 degrees would be around 35 PSI. Believe your switch has failed. It unscrews and another screws in, a shrader valve stops loss of refrig coolant. Wear protective PPE 'anyway for your eyes. High side PSI of around 180 PSI. Some running down the highway might read 220 PSI. IF switch failed or over pressurized, disconnect happens. If pump was continually running the PSI would build and when it expanded into the low side it would raise that PSI uncomfortably higher too. This might happen if it was cooler evening with the AC running full tilt. Not so good of an idea to do. PSI's will again return to normal with a good switch.

pecanflyboy

Thank you so much for responding so thoroughly. I get home Saturday. I'll let you know how it goes!

pecanflyboy

I'm seeing high pressure at the low pressure fitting, but I'm reading this is a possibility with the compressor not running....? I've jumpered the switches and the compressor will still not engage. Which switch are you thinking is bad?

papa tiger

If you can disconnect the compresser clutch , jumper it strait to the battery to see if it will engage the clutch. Try tapping it if it doesn't engage from the battery with the plug off. Sometimes the problem is worn clutch and it needs a little tap if it gets power. If you get it to engage at least you know it works, then jumper the switches one at a time. Have someone tap the clutch. If it is worn it may engage or not. If it engages it leaves out the PCM as a problem. Higher than normal PSI tells me it is a bad switch, and was not cycle last night. Hook up your OBD II code reader, you should have P1461/P1469 codes there, showing the nature of the Malf.

pecanflyboy

If I discover that the compressor is getting power, can the clutch be replaced without removing the compressor?

pecanflyboy

I dodged a huge $$$$ bullet!


I violated my KISS principle...Keep It Simple Stupid!


After spending several days out of town, I came home and immediately began working on my AC, armed with Papa's great advice.


Instead of jumpering the compressor to the battery, I decided a much easier way to test the entire electrical integrity of the system was to remove the plug at the compressor and put a volt meter on the leads. With the engine running, you should see 0 volts with the AC off, and 12-14 volts with the AC on. This checked out, so I new that my problem was something mechanical in the compressor/clutch.


I had only taken a quick look at the clutch, before, to make sure it turned freely. This time I looked more closely and noticed the retaining bolt was missing from the clutch plate. I reached up and the plate fell off in my hand! I found a 10mm bolt, made sure I still had the shims, reinstalled the plate, torqued the bolt........SHAZAMMM! AC works like a champ!


The lucky part is that I probably drove the truck for more than 200 miles without the retaining bolt and the clutch plate didnt fall off! Thanks for all the help.



In summary, I would troubleshoot the AC as follows:

1. Take a close look at the mechanical condition of the compressor. Does the clutch turn freely and is it secured to the compressor. Is the clutch engaging with the engine running and the AC turned on?
2. If the clutch is engaging, then it's time to check the system pressure. You can use the gages that come attached to your refill bottle purchased at WalMart of and auto parts store.
   1. Find the low pressure service port which is against the firewall, passenger side, connected to the AC dryer/accumulator can. If the servicing line fitting does not slip on easily, it is not the correct port.
   2. Engine running, AC Max, clutch engaged, you should see around 40 - 55PSI.
   3. If it's high, you might have an orifice problem
   4. If it's zero, you need to have the leak found, the system vacuumed, and reserviced.
   5. If it's low, you should be able to add to the system using your refill can.
3. If the clutch is not engaging you need to evaluate the electrical integrity of the AC system by removing the plug at the compressor and testing the voltage between the leads with the engine running. You should see zero Volts with the AC off, 12-14 Volts with the AC on.
   1. If the electrical integrity of the system is good after the above check, look into replacing the clutch. You should be able to do this for around $100 and not have to remove the compressor from the car. Next would be to replace the compressor which will require you to offload the R-134, vacuum, and reservice.
   2. If you do not have voltage at the plug with the AC running, you may have an electrical problem.
      1. In the engine fuse box my system had one 15 A fuse, a relay, and a diode. Check these components. You can buy new stuff, or swap like parts with other plugs in the fuse box.
      2. Next, check the Low and High pressure switches. These are designed to keep the compressor from running if the pressure is low. The low pressure is behind the dryer/accumulator, and the high pressure is near the HP service port in front of the battery. Unplug. Take a paper clip and jump the leads. If the switch is bad, the jumper should allow the compressor to start.

If it's still broke, keep asking questions. Good luck!

Jimmy

papa tiger

Hope your not missin a lot of parts. Good luck,