5.00pm Friday at 26 degrees C, driving home in stop-and-go traffic (mostly stop) on the A38 and coming up to the Markeaton roundabout: It's hot. Fortunately, the air conditioning is blowing cool, sweet air and all is good. Then there's a muffled *pop* from somewhere down below and the A/C starts shooting wind hotter than a curry fart with added botulism. Nice. Not.
I drove home knee deep in sweat. After a few minutes of electrical diagnostics too tedious to relate here, I determined that the pusher fan resistor had failed. The pusher fan sits in front of the radiator and A/C condenser. When the A/C is running, the fan operates at half speed to keep air flowing over the A/C condenser. That cools it. If the fan stops running, the condenser gets too hot, which causes the gas pressure to soar in the A/C refrigerant tubes and a pressure release valve pops in the A/C compressor. The valve relieves the gas pressure so the compressor and other expensive bits aren't damaged, but it leaves insufficient refrigerant in the system to cool anything. At that point, summer begins to suck, driving-wise.
Now, that resistor: I mentioned the pusher fan runs at half speed. To run the fan at half speed, current is run through a big, fat resistor mounted on the pusher fan chassis. If the resistor burns out, the fan stops running and, as noted above, the A/C overheats and pops. That's what happened. So, a new resistor is needed.
If I were going to do this job properly, I'd pull an assortment of plastic shrouds and whatnot, and possibly the whole front bumper, to gain full access to the fan and its resistor. That's what I'd do if I were going to do this job properly. Usually, I'd do a job properly. BUT I WANT COLD NOW. This time, I have no patience for "properly". I'm going to do it the cheapest, quickest, easiest way possible.
I'm going to cut things:
That gives access to the resistor. The resistor was in the gap, but I removed it. You can see where I cut the fan guard to get at it and have left stripped wires ready to install the new resistor:
Here's the offending organ, the old resistor still affixed to its bracket. The shiny bits are where I'd started grinding off the rivets that secure it before I remembered to take a picture:
Sorry it's a bit blurry. I sneezed whilst I was taking the pic.
I know what you're thinking. You're thinking, "Hey, where are you gonna get an 85 watt half-Ohm resistor at 5.30pm on a Friday?"
Good question. I have a magic garage. In my garage, there is one of everything. EVERYTHING. I found a spare resistor of the right type and size:
Here it is mounted to its bracket:
Here's another angle, in case you're desperate to see what a machine screw looks like.
A bit of soldering and some heat-shrink tubing, re-mount the resistor in place, and here it is, running and doing its thing:
It looks like this through the grill:
Yes, I know I should clean off the bugs and whatnot. By the time you've read this, I might have done so or there might be new bugs splatted there. Who can know these things?
The next step was to re-fill the system with coolant from a can of refrigerant courtesy of Halfords, a process of decidedly dull simplicity. You simply follow the instructions on the can. Interestingly, if you return the can to Halfords you get a refund of £10. Not returning it would be unreasonable, because without the refund it would cost an outrageous £29. When I returned the can, the guy at the counter said he'd sold a lot of them, but I was the first person to return a can and collect the refund. Amazing.
It's joyously cold now, like driving with a refrigerator door open.
I know what you're thinking: Without the appropriate bits of fan guard in place, surely rocks, leaves, birds, small children, etc. will get sucked into the fan and impaled on the A/C condensor, no? I suspect not. The slats in the decorative grill aren't much larger than the slots in the fan guard, so the condensor is pretty much as well-protected (or not) as it was before. Anyway, those pusher fans are a rather weak item and it will surely fail in a year or two. It's probably starting to seize up, which is probably what killed the resistor in the first place. Then I'll pull the front bumper and replace the whole fan and the fan guard. Yeah.