CCU off but heat runs constantly. #5 fuse blown so I replaced. This corrected the problem for many miles until I reached 65mph and heat turned on. The ccu was always off. The transmission shifted fine at high and low speeds. The #5 fuse has a small break no burn marks. Any help will be appreciated.

That fuse also controls the kick down switch for the transmission. The kick down wires insulation can become worn and short when you depress the accelerator fully. That cuts power to the mono valve resulting in full heat.

Replace the fuse and drive the car without hitting the kickdown as a temporary fix. To replace the wiring you need to pull up the carpet from under the accelerator pedal.

Good luck!

__________________
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thanks, that sounds like a good tip. When the heat turned back on I might have just punched the pedal. Ill take it for a ride now and check it out. If this is the problem is the kickdown wire pretty obvious.

i just returned from 40 miles. The fuse did not trip. I drove 70 mph and nothing happened. I did use the kickdown repeatedly and it did not trip. I turned on the ac it did not trip. By the way my ac has not been working. I had the ac on and kicked it down repeatedly and it did not trip.
(I noticed the odometer roll over 299000 miles on this run. ill keep a camera handy for the big 30.)
Is there a series of tests to look for shorts?