I bought my twinco in Florida and knew it had a red tagged heater system. In Florida heat is easy to do without but I'm in Boston now and it's serious business. Initially I had budgeted about $2500 for the rebuild itself, including shipping. As you can see I missed it...by a lot!

Heater s/n1670715 modified to a 20D35-1....$1800
Blower.......................................................$0
Motor, OHC ................................................$450
Labor.........................................................$90
Regulator, new, with exchange......................$750
Shipping......................................................$85

Grand Total.....$3125 for the actual heater rebuild itself

The rebuild was completed by Aircraft Heating and Electrical, Inc. out of Redding, CA.

When I mentioned the final cost was well over the quote they reminded me that the blower motor is a separate system from the typical heater rebuild. I also learned that the regulator, once inop, can't be rebuilt per the FAA so a new one, built in 2002 or later, I believe, was required. Also I should mention the modification included a new ceramic heater can, avoiding the expensive testing required regularly. To the company's credit, they did give me a $250 goodwill credit when I asked for sticker shock relief. It was much appreciated and left me with a very positive impression. Their quote actually was accurate, my understanding of what was included in the modification was not.

I estimate for labor to uninstall old unit, ship, test new mod and re-install is about $700. All in all, at least for me, this was a $4k fix. But hey, at 10k feet and in the middle of a New England winter..the heat is priceless.

Hopefully this is helpful to the next Comanche owner who's considering this repair.

Now run by Harold Haskins Jr. I found him to be extremely knowledgeable. Ours was a few years back and I chose the get-rid-of-the-ADs route so I have less downtime during annuals so didn't do O/H and don't recall pricing.