MG Car Repair: Gauge lamp rheostat, instrument bulbs, resistance range

Question
The gauge lamp rheostat in my 1980 MGB has frozen solid.  Rather than pay $120 for an OEM replacement, I want to use one from Radio Shack.  Where can I get the specs on the part so I can get one with the correct resistance range?

Answer
Hi Billy,
I have several manuals on the "B" but couldn't find any quote on the resistance range. I probably have several resistors but they are packed away in boxes in a safe place. (safe from me)
I did however find a quote in an OEM manual of the Wattage of the instrument bulbs which is 2.2 Watt. With that figure you can arrive at about .183 amp per bulb. So just count the number of bulbs and since the bulbs are connected in parallel you multiply the number of bulbs by .183a and you have the total amp draw which should be the max amp draw. Divide 12v by that figure and you will have the LOW end resistance. I don't know what the highest resistance would be but a guess would be the use of 6v as the voltage. So you would then divide 6v by your max amp figure to get the max resistance.

If any of you out there have one out of a car, please take an ohm meter and measure it open and closed so we can have a real figure instead of a math figure. Send it to fitzcharlesh@bellsouth.net

Howard