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Discussion Starter · #1 ·
I believe I fixed a maddening parasitic drain on my 2004 MDX and wanted to convey the information should anyone else experience the same situation.

In May 2016, as the temperatures warmed up, I noticed the AC wasn't blowing too cold and gave it a pound of 134, which I thought was quite a bit considering the AC was fine before the winter. This fact will become important in a moment, and was one that I didn't realize the significance of until much later. At about the same time, the battery went dead, which I dismissed as a worn out battery and replaced it. A month later, my wife goes to start the car, but the battery is completely drained to the point where there is no juice in the battery at all. Not even the interior courtesy lights would illuminate. Being an eternal optimist, I replaced the battery hoping the battery was defective. Again, after 3 or 4 weeks and operating the car on a daily basis, wife goes to start the car and the battery is completely drained. Obviously, the battery wasn't a problem but the car was possessed with electrical demons. The rate at which it was draining was alarming because the battery was being completely drained in 8-12 hours, which I believed was creating a tremendous amount of heat causing a risk of an electrical fire.

I put the car in storage and for the next 18 months, and on about 20 separate occasions, I did a amp draw test with a multi-meter trying to locate the troublesome circuit. However, I never drew more than 40 milliamps, which was completely normal and reflected a correctly working system. Nonetheless, the battery would continue to drain with no identifiable rhyme or reason. The electrical issue was intermittent, and I would only be able to diagnose it when I had the good fortune of testing it when it decided to malfunction.

The solution finally presented itself when I was driving the car and noticed cold air coming from the vents, but the AC was not turned on. I turned on the AC, then turned it off, but still blew cold air. AHA! The air conditioning compressor clutch relay was faulty. The relay was sticking on and off, which was causing the compressor clutch to engage when the car was not running and causing the power drain. I believe the freon loss I experienced when the problems started was probably caused by an overpressurized AC system which consequently bled off, and caused a low amount of freon in the system. The AC compressor clutch relay was $15 at NAPA and is located in the fuse box. If your having a drain problem, and a drain test doesn't reveal an abnormal drain, then think of replacing this relay and see where you are. Its been a month now without a problem.
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