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Tuesday, September 16, 2014

Doug's Domain

Doug Vetter, ATP/CFI

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Saturday, May 31, 2008

Aux Fan Revisited

Yesterday while running a few errands during lunch I decided to use the air conditioning for the first time this season. Since I knew I had just repaired the aux fan I decided to flick the snowflake button on and walk out in front of the car to make sure the fan was working. To my surprise I found it at a dead stop. Since turning on the air conditioning turns on the aux fan I knew this was a problem, and sure enough I also found the compressor making noise indicative of higher than normal pressure in the system. I turned off the air conditioning to reduce stress on the compressor and pondered the cause while I went about my business and carefully watched the temperature gauge.

While doing the aux fan replacement I noticed the electrical plug fit tightly into the receptacle and required a lot of force to press together. In fact, I had to use a channel-lox pliers to press them together sufficiently for the plastic spring clips to grab properly. I was acutely aware at the time that the connectors might separate so I put a ty-wrap around the spring clips to lock the assembly in place. My first instinct in the troubleshooting process was that this connection had come apart.

Unfortunately, once I got home, put the car up ramps and managed to remove the panels I found the electrical plug in exactly the same condition I'd left it. The first troubleshooting step was to pull the plug to test for power with the engine running and the air conditioning turned on. Under these conditions I found 14 volts DC on one of the terminals (the low-speed side). This meant that the low speed fan relay and the associated fuse were in good shape, so the problem lay with either the fan motor or the electrical plug / receptacle assembly. I turned off the engine to reconnect the plug and then started the engine again to retest it. Thankfully, the fan turned on as expected, which eliminated the fan as the culprit. This little revelation caused me to breathe a sigh of relief because I'd just saved myself from the hassle of cross shipping the fan with a new unit.

Concerned that the poor connection might be due to oxidation on the older contacts of the plug I went over to my brother's electrical van to pull out out a tube of anti-oxidation paste (a conductive dark gray goo that we use whenever mating dissimilar metals like copper and aluminum to prevent corrosion). I used one of my picks (the same ones I use to remove snap rings or the o-ring on the oil filter cannister) to put a very small amount into each female conductor terminal located in the electrical plug. I inserted the connector into the receptacle several times before seating it for good and put a ty-wrap around the spring clips to lock it in place. I tested the fan one last time before I reinstalled the protective panels and called it a day.

I expect to replace this connector assembly with a new waterproof unit but that will have to wait until my schedule permits finding an appropriate part. The only thing that may make it difficult to find is the fact that it must support a minimum of 20 Amps DC continuous running load.

If I had brought this to the dealer they would have charged me a diagnostic charge of around $100 plus the labor to actually fix it, which could have been another hour, or $110. The total process, including searching for the anti-oxidation paste took me about 45 minutes, so I'll just conservatively call it $100 labor saved.

Mileage: 160680; Labor Saved: $100