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Checker Heater Operation

Copyright 2017 - Andy Taylor. Used with permission.

It's getting it's time to service the Checker heater!

The Checker heater unit is a very simple device. I though I'd write a brief bulletin on its operation.

The unit consists of the following mechanical parts:

Three cable controls HEAT - controls water valve, flow to heater core

HEAT-DEFOG( - goes to flap valve on left side of heater. When closed, diverts air to defog manifold in dash under windshield. AIR - opens/closes flap valve in cowl in the inlet side of the blower. This connects to duct hose that leads to the right grill fresh air inlet.

Its important to make sure this duct hose is intact under the front fenders. its the only way the blower can intake fresh air, with it missing, the heater will still work somewhat, but can also cause the blower to pull engine gases and smells into the passenger compartment.


Blower motor (same as 1973-1980 Chevy truck). Low-medium speed resistor (located in front heater cover) similar to 1960-66 Chevy truck, uses both resistor for low , both in series for medium speeds.

Heater switch


Proper thermostat. If coolant cannot get hot heat!

Blower must be operating at speed and pulling in fresh air THROUGH THE GRILLE AND NOT THE ENGINE COMPARTMENT!

"AIr" valve must be fully open and fresh-air inlet hose must be present.

Water valve must be fully open, with no restrictions. No circulation through heater heat. Heater core must be clean of debris, dirt, daubers, nest, etc...and no restrictions. Blower Air must pass through the heater core. Pull off front cover, and clean/inspect.

Mechanical cables must be free and working,. Newer cars used pneumatic actuators operated from engine vacuum. Retrofit possible??

The better (tighter) the door/window trim is, the better the interior will hold heat. It's hard for the heater to compensate for leaky, drafty door/window seals.


Modern cars heater blowers operate at much higher speeds than the original Delco blower motors. With a little modification, I used a blower unit from a 1995 Honda accord. it GREATLY improved the performance of the heater.

I'm sure other modern blower fans will work...but observe rotation, fan diameter, and depth...and air flow direction. Some wiring modification & drilling may be necessary. To my knowledge, there is no direct replacement for the heater core.

Comments from Facebook:

John Weinhoeft - Group Moderator: Which also brings us to the discussion of the wire cable used to control the heater valve. That cable has a circular loop at the valve end to go over a round post. Plus some cables have a stair-step on the end of them to go into a hole and hook on.

If you have ever tried to put a loop on the end of a metal cable, it is almost impossible to do. Same for bending a stair-step. There is actually a special tool for it. K-D #495

Andy Taylor This tool looks very similar to what is called a "stringers jig" " used to restring pianos. The coil of wire around the tuning pin is called the "becket." I think a person could use an autoharp tuning pin (which is closer to the diameter of the coil on the heater control) to insert the wire in the pin, crank the pin in the jig a couple of turns, and that would do it. The jig for the piano string is very easy to make. I think a mini version of the coil jig would do the trick.

George Laszlo - Group Admin So what's the best way to lubricate/free up the mechanical cables?

John Weinhoeft - Group Moderator Remove them and soak in a bucket of penetrating oil is the best method.


Here is the heater valve application. I posted this in another group a few years ago. took a while to find it..They were on the old laptop Ron Leatzthe valve will work without modification,except on and off will be reversed.

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