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By Jeff Zurschmeide

One area of restoration that is often overlooked is the car’s heater. After all, most restorations are driven only in the summertime and never during very cold weather, and many of these ancient heaters don’t kick out a lot of heat at the best of times. So it’s tempting to ignore the heater or give it just enough attention so it’s not dumping Prestone on your feet.

This is a mistake, and for precisely the reason most people ignore the heater: if you drive your car only in the summertime, your car’s heater core is an additional radiator that can be used to draw heat out of your engine. That’s true for air-cooled Volkswagens and Porsches (and Chevy Corvairs) as much as it is for conventional water-cooled cars. You can drop your engine water temperature by 10 degrees or more by running the heater in the cabin.

Of course, if your car is running hot because it’s 100 degrees outside and you’re stuck in traffic, you’re likely to cook yourself until you’re medium-rare, but that’s a sacrifice most of us are willing to make.

Even if you never have to use it, a good working heater is an important engine cooling safety item. But it’s also nice to be able to kick on the heat in the cold morning on your way to a car show or just on an evening drive through the country.

You will also find that your heater works better and produces more heat if you’ve restored it with the same care you put into your radiator. Heater cores have been processing the same coolant as the radiator for the same amount of time, and if your radiator was clogged up, then your heater core is as well. And if your heater blower has become feeble over the years, a new motor or just some attention to the ground wires and controllers can restore a healthy breeze when you need it.

When you restore your heater core, take it to the radiator shop along with your radiator. They’ll be able to clean or replace the core for you. Then, when you reinstall the heater core, use all new rubber tubes and hose clamps to make sure your new installation doesn’t leak. That core is under the same pressure as the rest of your cooling system, and requires the same attention to detail.

Hook your heater blower up to a 6 or 12 volt (depending on your car) battery on your workbench and see how it blows. If it’s blowing harder than it seems to in the car, chances are you just need to improve the grounding to get it working as it should. But if it’s tired, you can often find a new replacement motor if the stock ones are no longer available. A junkyard blower motor might work, but more often than not they’ve got the same problems yours have.

Ducting from the heater in a classic car is almost always simple - just straight out through the dash or under it, and another duct up to the windshield for defrosting/defogging. If you have to choose, make sure your heater can defog the windshield - that’s a basic safety issue. Products like Rain-X and other anti-fog applications also help a lot.

As you inspect the heating and defrosting setup, make sure all the intakes (generally just underneath and in front of the windshield or at the front grille of the car) are free of leaves, pine needles, and other obstructions that get sucked down and block airflow. Also make sure any drains for condensation and rainwater are clear of dirt and debris. Some cars, notably Alfa-Romeos, will allow rainwater to flow down the air intakes right onto the electric blower motor if the drains become clogged!

With just a little work, your car’s heater will last the lifetime of your restoration. It will keep you comfortable on chilly days and in a pinch, it can save your engine from costly repairs. That’s a good investment either way.

Dos and Don'ts
Thumb up  DO
  • Treat your car’s heater core with the same care you use on the radiator
  • Replace all rubber heater hoses
  • Pay special attention to the wiring and the blower motor
  • Make sure your defroster vents work, if nothing else

Thumb down  DON’T
  • Don’t decide you can get along without a working heater
  • Don’t allow a slight heater leak to persist
  • Don’t allow leaves or other material to block vents or intakes
The Popular Restorations Feature Car
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1946 Packard: Restoring the heating system



When it came to heating, the Popular Restorations feature car presented a bigger challenge than most collector cars. When equipped with the heater option, 1946 Packard Seven Passenger sedans have not one, not two, but four heater cores: one for the front heater/defroster, one for the heater under the driver’s seat, and two under the back seat.

An interesting feature of the cabin heating system is that there is no “Cool-Heat” lever as with later cars.

The lever typically opens and closes a valve that allows more or less coolant to flow through the heater core(s). The Packard has such a valve but its control is at the engine head. The idea was to shut it down during the summer and then open it back up during the winter.

To restore the heaters I took each one apart and tested the motors, which hadn’t been run in years. At first they started out slowly but after a few minutes running time each one came up to speed. The sheet metal enclosures for the front heaters were somewhat rusty so I sent them off to be powder coated. The powder coater offered a brown color, nearly identical to the original color.

I had the cores checked at Mac’s Radiator and two needed to be recored. And when I got all of the parts back and installed the heaters they all worked fine. As you would expect, I replaced all of the heater hose and clamps. To reach all of the front and back heaters I needed 40 feet of hose and ten hose clamps. You can find period-correct clamps at Chev’s of the 40’s, which is an online outfit but their warehouse turned out to be just 20 miles away.



Able Radiator Repair

By Jeff Zurschmeide

Tom Shauvin
14511 SE River Road
Milwaukie, OR 97267
(503) 652-2707

PR: Should people service their heater core at the same time they work on the radiator?

TS: Not usually. The heater core is separated from the stressful things that happen to the radiator. They’re better-mounted and they have to flow less fluid than an engine radiator, so it doesn’t build up the friction you see in a radiator. So you generally will see a heater core last 2-3 times the life of a radiator.

PR: But most old cars being restored will have been in use for decades, so is it a good idea to look at the heater?

TS: We start looking at corrosion being the big issue when a car is more than 25 years old. Heater cores have a pair of end shells and then a core between them. Heater cores from the 1910s through the 1980s used a cellular core rather than a tube and fin design, and now we’ll replace those old designs with a new tube and fin core. The old cellular core designs are going away -they’re just not being made any more, so people shouldn’t be afraid to change to a tube and fin design.

PR: Can you use sonic cleaning or solvents to clean a heater core?

TS: Occasionally we’ll use Muriatic acid to get rid of oxidation, but acids don’t really remove rust. And anything that will eat the steel will also eat brass. We use the muriatic acid to clear solder bloom, which is lead oxides. But acids can also cause leaks.

PR: Anything else people should know?

TS: Keep it clean and keep it full of anti-freeze and water mix. Using anti-corrosion additives is always a good idea, and commercial anti-freezes have those additives, so use the proper mix of coolant for best results.

PR: Anything special for restoration projects?

TS: Yes, inspect everything! If you’re already tearing up the interior of the car, make sure you take the heater core into a shop and have them check it out. The worst thing about anti-freeze is that really accelerates the growth of mold and mildew because it’s a sugar compound. Bacteria can’t tell the difference between anti-freeze and sugar water, and it can destroy your new carpet.

Click on any item below for more details at Amazon.com

Mike Stubblefield, John H. Haynes, John Harold Haynes
The Haynes Automotive Heating & Air Conditioning Systems Manual
Haynes Pubns, Paperback, 1994-01
This is an excellent book. It is outdated but that may be helpful when restoring older cars. It is mostly for R12 systems.

Steven Daly
Automotive Air Conditioning and Climate Control Systems
Butterworth-Heinemann, Paperback, 2006-10-03
A complete text and reference on the theoretical, practical and legislative aspects of vehicle climate control systems for automotive engineering students and service professionals.

Thomas S. Birch
Automotive Heating & Air Conditioning (5th Edition)
Prentice Hall, Paperback, 2009-02-19
This book is correlated to NATEF and ASE and provides a complete, state-of-the-art source on automotive heating, ventilation, and air conditioning systems.
External Links

Classic Radiator and Heaters sells radiator cores and blower motors for older cars.

Chevs of the 40s has period correct hose clamps for that era.

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