Looks like our 1975 dryer is working as designed (almost). It took 15 minutes to get to the problem which was a bad control switch (timer). I priced new switches and the price ranged from $208 to $150. If I sent our switch in and they could rebuild they would likely charge $74 or for $20 more I could get an immediate rebuild but would still need to send mine in. (The original part is no longer made so they have substitutes that fit, they say.
The dryer has been an excellent machine. It is a Maytag model kde407 series 01. As I understand it moves a lot of air and does not get the clothes too warm while drying which makes it good on the clothes and efficient also, as moving air is cheap compared to heating air. The unit is rated at 4800 watts which means it could draws 20 amps at 240 volts. The spinning motor runs on just 120 volts. There is a heat temperature switch which I suspect cycles the heating element on and off keeping the air at a controlled temperature. Then there is another overheat switch in case of a malfunction. I am pessimistic a new machine would be more efficient.
After taking the control switch apart I found that the two inch plastic disc had separated from the splinned metal shaft causing the failure. The disc controls all the length of times for the different drying cycles and also turns on the heat if needed for any cycle.
After a little research I decided to glue the plastic disc to the metal shaft using JB Weld. I let cure overnight. I was aware before gluing that I had no idea how to align the plastic disc to the shaft and if out of aligned it would skew all the settings shown on the control panel. Oh well it would have taken too long to research that out.
While putting switch back together I noticed the spring had sprung off somewhere! (Kids - oh phooey - probably can’t blame it on kids or grand kids.) I remember just where I had left that spring but likely when I vacuumed everything I must have tipped the spring out of place. So then comes out the 2 million candlepower flashlight to search the floor and shine in the small opening to see inside the dryer. No luck. So now another 10 minutes to get the back off. I found the spring easily and went ahead and vacuumed all out which included 39 cents, 3 allen wrenches and two buttons.
So, now all is back together and the dial is 10 degrees off and after testing I suspect everything is working. I did place a new mark on the base of the control dial indicating the setting point of the switch. A good thing is the little black mark I added does not seem to clash with the avocado green dryer.