Heater issue....1964 Plymouth...so simple yet so difficult :)

Several years ago, I rebuilt the heater in my 1964 Plymouth with some great help from Kevin Merkley up in Thunder Bay, Canada. I used a new core and a rebuilt regulator. Anyway, the heater has never produced heat like my original car did back in 1964. That thing would literally cook you out. I'd looked under the dash more than once and could see the regulator on the heater opening and closing as I worked the heat control lever, so figured it was okay (lesson to be learned here!)

I'd like to drive my car more in the fall, winter, and spring so determined I had to figure this out.I mean, how hard could it be? Well, I found out :)

First, I drained the radiator, unhooked both hoses from the heater and pushed compressed air through the unit. Worked okay, but that's not a true flow test, so

Next, I hooked up both hoses back to the heater. I unhooked the block-end heater hose that returns coolant to the motor from the heater core, and stuck it in the radiator fill neck. I put a stopper in the discharge port of the block so nothing could get out of the motor. Refilled the radiator and started the car with the heater control valve lever on the dash all the way open (down in my case). Well, there was only a trickle of coolant coming from the heater back to the motor.

I "assumed" something was wrong with the regulator or the core. You can't back flush these units as that action tries to close the regulator. It shouldn't have needed it anyway, but felt I was running out of options, so....you know it's coming, took the heater unit out of the car completely. I couldn't find anything wrong!!! I even took the unit to Jeff Carter at JC Automotive in Lynwood, WA. He tested it and said all was good. He told me to carefully check the throw on the regulator once it was back in the car, to be sure it was completely open.

Another several hours reinstalling the heater, hooking it all up, fill the radiator and start the car. THIS TIME, I did not hook up the cable that runs from the dash lever to the regulator under the dash. I mocked it up and held the regulator cable where it would rest when hooked up to the regulator bracket and GUESS WHAT??? The wire that slides back and forth within the cable would not open the regulator fully. It was about 3/4" short. It would barely open the valve. I manually opened the regulator valve to full flow and the heater started working correctly immediately.

So, what was the issue?? The problem was that the remanufactured regulator I used was configured differently than the one that came out of the car. The remanufactured unit had a "stop" on it, a perpendicular metal tab that stopped the cable while allowing the controller wire to move back and forth. I broke off the little piece of pot metal, manually opened the regulator valve on the heater completely, then clipped the cable to the regulator. The heater now works PERFECTLY!

I told Gary I should have taken pictures along the way, but didn't, so this little missive is just meant to pop on a mental light bulb if you decide to replace the regulator on your Mopar heater. Check the throw on the regulator FIRST, not LAST! It might save you hours and hours of frustration.

Happy New Years everyone.

/Butch Edison