Defrosters
by Mike Olsen
During some of the warmer days in March I took my MGB out for a ride. It was nice to get into the drivers seat again. There was a small problem however, the defrosters didn’t work very well. They didn’t do much all. I had to use a towel to clean off the inside of the windshield.
Utilizing my most common type of trouble shooting (throwing it against the wall to see what sticks) I removed the fan motor and rebuilt it. I thought if I had more air flow I would have more defroster action. This did increase the amount of air but had little affect on defroster function.
At the club swap meet I had picked up a heater valve and decided this would be the next correction to be made to the system.
The heater hose had felt warm but not hot so I guessed it must be a bad design. I modified the heater valve by disassembling and placing washers under the valve cup. This is done to open the valve all the way. Most valves are closed at the half way point on the heat control knob and this modification lets the valve open fully.
Then I removed the old valve and looked into it. It was full of JUNK. There was a very small hole letting water through about 1/8th inch. There was nothing in the hose or the head. So I had finally found the problem. I installed the new valve, turned on the heat and fan and it worked great. As time permits I will flush the cooling system to clean out any debris (sounds like an April type job).
The lesson I learned was not to over look the obvious and assume. I seem to have to relearn this every once in a while. Also, systematic trouble shooting is the best way to locate and fix a problem so you can drive the car instead of spending a beautiful day repairing the car.
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