Hello.

I have searched through this forum and have not seen any discussion on my particular issue, thus a new thread:

2005 F-150, 5.4L, King Ranch
A/C is the electronic controls (not the dials)

Problem: Push buttons to turn on the A/C. A/C comes on at 75 degrees on the digital readout. A/C stays on for anywhere from 3 seconds to 25 seconds and then turns off. The electronic control turns off (no lights) and the air stops blowing out of the vents. If you turn it back on, it does the same thing. If it stays on long enough, I can feel cold air blowing. I've tried using it at different temperatures and fan speeds with the same result. The A/C controls and airflow turns off after a few seconds.

Troubleshooting:
1. I tried disconnecting the battery at the negative cable for 30 minutes. No change.
2. I tried using the A/C by turning the key up one click (engine isn't running, controls are on battery power). No change.
3. After researching, I read a lot about replacing the blower motor resistor. I purchased this one from Auto Zone and installed it. No change.

I am looking for suggestions before I take it somewhere. Any thoughts?

Thank you ahead of time!

 

Any help would be appreciated.

 

Check your battery condition (capacity) and verify the alternator is properly charging the battery. EATC modules tend to go brain-stupid if they don't have enough power.

If that passes, check all grounds and power feeds to the EATC module. If those are good, then you likely have a failed EATC module but there are specific diagnostics checks that should be doe before making that determination.

 

Thanks for your response.

I spent some time with my multimeter checking as you suggest.

1. My battery and alternator are in the putting out the appropriate voltage. That seems likely not the issue.

2. I accessed the rear of the EATC and checked the power and ground and both seem to appropriate.

3. While I had access to he plugs, I put a bit of dielectric grease, re-attached, and then tried the A/C again. The unit stayed on for 30-45 seconds (longer than it had) and was blowing cold air.

So, it sounds like maybe it is the EATC module? I found another thread that said you could do a diagnostic test by pushing "off" and "defrost" simultaneously with the key click up to acc. I got nothing when I tried that.

Thoughts?

Thanks again!

 

You can't load test a battery and alternator with a multimeter, you need a load tester. Parts stores do this in the parking lot free of charge.

 

Double check your procedure for initiating the self-test, something doesn't sound right with what you described. You will have to do it while the unit is powered up.

 

Thanks for all of the responses.

I found a used EATC module on eBay for $90 and made the purchased. Upon installation, my problem seems to be resolved. I will report back if it starts acting up again. Thanks again for the assistance.