Wednesday, September 14, 2011

1964 to '67 GM Plastic Heater Control Parts


Maintaining 1964 to ’67 GM plastic heater control parts

Story Jim McGowan

For some reason, the designers at GM decided to use some plastic parts for the dash control levers in many 1964-’67 A-body cars.

The levers at the heater box were metal and durable over the years, but the levers at the assembly, controlling the opening and closing of the defroster baffles and temperature control, were plastic. They probably never dreamed that cars from that era would still be around almost a half-century later. So at the time, plastic was a cheap alternative. They were wrong and we’re in trouble.

Last winter, I was driving my ’65 GTO and wanted some heat. I moved the control lever in the dash and felt the normal resistance, and then bang, the lever went completely to the other side of the control panel without any resistance whatsoever. I knew that something had broken in the cable-operated control assembly. I had lubricated all those controls about 10 years ago and forgot about them. Well, that was a mistake.

After crawling under the dash, I found the problem. The control cable wires have a loop on each end that slides over a plastic pin, which is part of the lever. These controls are now ancient plastic, which has dried out and is brittle with age. A control lever corner and pin had broken completely off. Had I been more pro-active lubricating these parts, this probably wouldn’t have happened. The problem is that it’s difficult to get at that these parts to lube them with the dash in the car. It will all have to come out for the damage to be repaired and the assembly properly lubed.

In this case the instrument cluster is fairly easy to remove; it’s a little more complicated with the larger, later-model clusters. I’m using Justice Brothers JB-80 on all the moving metal controls and their aerosol White Lithium Grease on the plastic controls. You can also squirt the JB-80 inside the cable covers to help the cables move more freely as well.

From now on, I think I’ll repeat this exercise every four or five years to be safe. Since these controls don’t get much use, old grease and other lubes can actually dry out and cause harder cable activation. So regularly lube them or lose them.

1 The heater/defroster controls are located at the right side of the dash cluster. Two slide levers that push or pull the heater box control assemblies activate them. The ’64-’67 A-body controls are all similar to these.

2 In order to easily access the controls for one of the baffle doors on top of the heater box, remove the glove box insert. It only takes couple of minutes and gives you a direct shot at the assembly.

3 Here’s the dual slide lever assembly behind the glove box. This one is all metal, and can easily be thoroughly lubed with aerosol white grease. Note the wire loop over the metal pin on the lever. A tab with small screw holds the cable in place on the box. Remove the screw and pull the loop free of the pin. Apply a good dose of grease under each moving part and work it in by hand.

4 Remove the screws holding the dash cluster and unscrew the speedo cable. Then pull the assembly forward and pop out the light bulbs, unplug any switches and remove the two other cables attached to the box on the driver’s side. A towel will protect the steering column from scratches.

5 This is the cluster with the three heater control cables visible. Label the cables before removing them so you know which goes where.

6 Here are the two aging plastic lever assemblies. Notice the lower corner of the right assembly. I initially used Superglue to reattach the broken corner and then applied a layer of JB Weld all around the area where it cracked. A healthy dose of Justice Brothers White Lithium Grease was added at all the pivot points of the plastic and metal levers.