Heater Box Repairs

Like most components on this car, the heater box has seen it's share of neglect and abuse. Someone has been into in the past, perhaps for a new heater core or to just try to figure to figure out why something didn't work. Probably started when the heater blower motor seized or vacuum controls got sticky, or wiring fried.

In any case, the fiberglass housing was severely cracked and broken in numerous places. A couple of the mounting studs (that hold it to the firewall) were completely broken off with chunks of fiberglass still attached.

I sent old seals and gaskets off to Detroit Muscle Technologies months ago for them to recreate. Much of them were part of the HVAC system and found in the heater box. Sadly, they haven't responded to any emails or attempts to phone them so I may end up making all of my own - we'll see.

In the mean time I'm attempting to repair and restore the box. With all the cracks, breaks, and missing bits it's pretty flimsy. But, with the help of fiberglass mat and resin it's shaping up nicely.

Most of the repairs are on the inside where they won't be seen. By necessity, some are on the outside which will serve to add much needed strength and reinforcement. Little will be visible once it's fully reassembled and painted - and even then you'll have to be standing on your head under the dash to see it.

Topcoating the firewall

Austin and I spent a couple of hours this afternoon during his Christmas break doing some odds and ends. He's a real trooper 'cause this kind of stuff is boring for a kid his age. I handed him some Eastwood Rust Encapsulator and had him topcoat the firewall and underdash area that I had previously treated with a rust converter (for mild surface rust). This will seal it and give it a uniform appearace. We're still cleaning paint out of Austin's hair.



Austin applies Eastwood Rust Encapsulator

 Meanwhile, I removed the e-brake assembly and cable, finished the resto on the AM Radio, and repaired some broken plastic tabs on a couple of the dash bezels.

AM radio ready to go back in

To repair the plastic tabs I'm trying a product I hadn't used before called, Rapid Fix. It's basically a super glue with a powder filler. It works very fast and seems to create a strong repair. We'll see how it holds up but so far I'm favorably impressed. It's similar to another product called Plasti-Fix which I used on my Duster project. I can't say yet which one I like better. You can get a better than website price on the Rapid Fix by shopping around.

In this case I created a dam with tape and then began alternately applying powder and glue to build it up. After it cured I was able to easily grind it to the shape I wanted with a 2" Roloc disc.

Rapid Fix before grinding/shaping

A/C Heater controls

Like most stuff on this dash, the A/C Heater controls were really fubered. The vacuum switch was physically broken and my attempts to disassemble and repair it failed. It worked better than before but just didn't operate smoothly enough to reuse. If you've never been inside of one, they're pretty interesting. You can still buy them new from the local parts stores but fortunately I had one from a donor.

A guy in the neighborhood has a '71 Dodge Polara parked next to his house that he plans to demolition derby next summer. It was in pretty good shape and it's a shame, really, to waste a perfectly good car. But since he plans on gutting everything and literally throwing it away he let me salvage parts from it for free. (When he's done destroying it I'm welcome to salvage the drive train). I pulled most of the dash and the heater control has the same vacuum switch as my original. It works very smoothly so I swapped it in.

Swapped in a vacuum switch from donor

The heater blower switch was siezed. There were obvious signs of overheating and when I opened it to see if I could salvage it, it crumbled apart. Most of the wiring in the heater related circuits show signs of too much current flow at some point. I don't know what someone was doing but would explain, in part, why the dash is such a mess. In any case, since the Polara switch is different , I had to replace it with a new one.

Original switch is toast

With some touch-up with a silver paint pen, the A/C Heater controls look like new again and should actually work now.

PCB repair

The gauge cluster has a quaint little printed circuit board on the back. All four pins on mine were loose. Loose pins can cause all kinds of problems with your instruments. The pins are simply swaged on the back of board and it doesn't  take much connecting or disconnecting of the plug to loosen them. Some of the swaging was missing and when I attempted to re-swage others, the metal fell off. As you can see in the pic below there isn't much left.

Not much keeping these PCB pins secure

I lightly media blasted the connections on the board to remove corrosion. Very fine sandpaper would be safer but this way I was able to get into the nooks and crannies and clean the female terminals. A dab of flux applied with a toothpick at the base of each pin followed by some solder re-established a good electrical connection and firmed them up. Glue on the back side added strength.



Solder re-establishes a good electrical connection to the PCB foil traces

I finished assembling the very basic gauge cluster, tested continuity, made sure there were no shorts, and bench tested the fuel gauge. Good to go. I think there are more idiot lights than gauges in these things. Next up: Dash switches and heater control.


By the way, the mechanical voltage limiter on the back of these panels can be a source of gauge trouble too. Mine works but I may replace it. I've made my own solid state version in the past and there are companies that sell electronic versions as well. I ran across this a company called Real Time Engineering that makes one of the most sophisticated ones I've seen. Not cheap but might be worth checking out.

Cluster resto

In the last post I started the cluster resto by stripping the old finish and someone's "paint job" from the bezel with a water based graffiti remover.

I disassembled my original cluster the donor to compare the pieces and select the best parts to build one good one.

Warm, soapy water removed most caked on grime

After washing both lenses to remove some serious dirt and grime I found my clear lens had some light stress cracks in the face. Some knucklehead felt compelled to push on the lens wherever a gauge was located. The donor lens had some deeper scratches.

Cluster lens looking like new

With a little spit, some 2000 grit sandpaper, and a soft buff wheel with plastic rouge I was able to bring the donor lens back to like-new condition. I had to touch up the white paint of one letter on the back side of the lens. You can do it all by hand but the buff wheel makes quick work of it and takes care of flaws that are difficult to remove by hand. You just have to be careful because you can burn the plastic if you apply too much pressure or hold it in one spot too long. I happened to have a Novus 3 part plastic resto kit which I used to do final polishing on the lens by hand.  There are several products for polishing plastic available at your local auto parts store. Some work better than others.

Novus Plastic Polish System


The face of the donor speedo was in slightly better condition than my original so I removed the odometer and tripodometer and transferred them. Remove two small screws and each tumbler drops out as an assembly. I also reset the odometer back to zero. It was a bit like a Rubik's cube but once I figured it out it was easy - much harder to describe. It did involve rotating the tumblers starting on the left. Before someone screams, "You broke the law!" I'll add that here in Washington, due to it's age, speedometer readings are exempt and I have no intention of passing this car off as a low mileage original. I just want to start the clock over when it's reborn.

I synchronized the tripodometer to the odometer so that it advances at the right time. This was easy enough to do by rolling the "tenths" tumbler on the tripodometer by hand without disassembling it. I hooked a drill up to the old speedo cable to test everything.

One freshened-up speedo to go

Stripping a dash

Along with way someone decided to do a color change on this old girl. Car was orginally gold on gold. When they painted the exterior red someone went crazy with black dye or spray paint on the interior. Since the plasticizers in '69-'71 dash pads are known to come to the surface and create a sticky goo you can imagine what happened when they painted it. Yup, we have a black sticky goo covering everything. It's like tar in spots. Flat black spray paint also coats the plastic bezels, including the raised lettering, with a generous amount of overspray on the switches and clear lenses. What a mess!

I picked up a cluster/bezel on ebay that was described as one of the best original speciman's the seller had ever seen - better than most he had seen at car shows. Silly me.

Seller thought this was better than most he'd seen at car shows. Hmmm, really?

Fortunately, UPS broke it in shipping so I got my money back and rather than throw it away  it became a donor for a few select parts.

Anyway, back to stripping. Lacquer thinner does a decent job of dissolving dried spray paint but it can also attack some types of plastic. No problem on the dash pad and useable on the vacuum plated bezel if done carefully but it will cloud clear lenses. Also, at $15+ per gallon it can get expensive. I think I've found something better.  I found a product at Lowes called Motsenbocker's Lift Off 4 - Spray Paint/Graffiti Remover. It's water based, biodegradable, and contains no nasty solvents. While I'm certainly no tree hugger the stuff works surprisingly well and is easy on the nose and skin. It dissolved all the paint right down to the vacuum plating which I wiped off with paper towels after multiple applications. Should work on the dash pad too.