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Article: Heating your Beetle
Last updated: 10/30/01
Symptom: You are cold
in the winter; your girlfriend/wife doesn't want to ride in "that" car;
you are no longer amused by the ice crystals that form on the inside of
the windshield when you breathe on it.
This is probably one of the
most often asked questions about bugs and it aggravates me. It aggravates
me because sometimes I hear really stupid advice from people who live in
areas where they don't even need heat. And I get just a bit aggravated
when I hear people comment "Beetles don't have heat, do they?".
I drove my '68 winter beater for four years in northern New England. This
period included the winter of '94-'95 which during the entire month of
January, where I live, the temperature never got above 32 degrees (F) day
or night. I performed the same modification to 3 of the Beetles that I
drove over 13 years, and it was always adequate, even in the northeast.
A Primer on VW heat
Prior to doing anything with your car, you must understand the dynamics of the heating system in the Beetle. Most of the air output from the fan housing is directed down through the engine cylinders, heads, etc. to keep the engine cool. But in the 40hp and newer ('61 and up) engines some is ducted out of the housing through those little "arms" (that what they always looked like to me) in the front of the fan housing. These were known as the "fresh air" systems. Via the 2" hoses attached, air is blown from these ducts through the heater boxes. Heater boxes are simply housings around the exhaust pipe that connects the exhaust ports from your front most cylinders to the muffler. The pipe inside housings have big, fat fins on them to allow good heat transfer. These heat up really fast. The hot air leaving the boxes is routed by the heater control box which is the little "head" on the back of the heater box with the lever that the heater control cable connects to. When the heat is off, the hot air is just routed out underneath the car. The heater box is part of the cooling system for your engine. Even if you never want heat in your car, you should keep those hoses from the fan shroud in place to keep air flowing through the heater box (or replace the boxes with "J" pipes). Without this, your engine may run hot and you may have warping problems as your heads heat up. When the heater control flaps are open, hot air is ducted into the passenger compartment under the back seat and into the heater channels to the front of the car. It comes out on the floor in the front and is also ducted up to the windshield via hoses inside the A-pillars. Keep in mind that the volume of hot air that is blown into the car is dependent on the fan in the fan shroud, which is dependent on the engine RPM.
In case you are interested, the '60 and older engines had what is referred to a "stale" air systems. Many who have these engines and depend on them for heat would call them "smelly" or "oily" air systems. This is because the some of the same air that was used to cool the engine cylinders and heads was also ducted into the passenger compartment when the heater flaps were open. This was fine for the first few hundred miles of the engine's life after which it got oily and smelly, especially when hot. These earlier heat exchangers essentially used "J" pipes (fin-less, straight pipes from the forward exhaust ports) and didn't tap the hot exhaust manifolds for heat. While the heat from them was weak compared to the newer designs, a good pair of 36 hp heat exchangers fetches a good dollar these days.
That is how it is all
SUPPOSED to work.
Problems with heat
With this knowledge you should now be able to follow this air path and check out the entire system. This article is about FIRST insuring that the stock system, at least to where it enters the passenger compartment, is in proper working order. To that end, the following list leads you through the steps.
On the other hand, if you have
to drive this car in any weather that might befall you, and it is not a
vintage classic, and you don't have tons of money, tools, ambition, skills,
patience, etc. then some moderate modification is in order.
Hot VWs printed a letter that I sent them on this mod back in March (I think) of 1993. I for one will swear that the Beetle's stock heat exchanger output is adequate for any climate in the continental U.S. Will it match the heat output of a gas heater? No. But it WILL heat up the inside of your car in some damn cold weather.
A lot of air pressure is built
up against the nose of the bug at highway speeds, and if it is cold air,
you probably would like to keep it outside. No matter how much heat you
can get inside the Type 1, it will be for naught if you have the arctic
express blowing through your dashboard when you cruise down the road.
JC Whitney sells 2 3/4"
flexible duct hose for under $10. You'll want about 5 feet for each side.
This is that black "fabric wound on wire spiral" stuff. It is very light
an floppy. You can move it all around and stuff it under the rear seat
in the summer when you don't need heat. This increase in duct size and
decrease in length will more than double the amount of heat you get in
I used another, similar implementation
of this in my '67, but I didn't want to cut a hole under the dash. So I
mounted the blower behind the speaker grill to the left of the speedometer
so it could draw cabin air through the grill. I really think that a fan
will draw much warmer air from under the dash than via the speaker grill,
but with my '67, I couldn't bring myself to cut a big hole under the dash.
I am an electrical engineer and I can tell you that the electric "boosters" will never work. It is simple physics that says that you can never get enough energy out of you battery to generate enough heat to make a difference. A company that advertises in Hot VWs sells a range of boosters with their highest power unit consuming 960 watts of power from the car battery. Do the V=IR math and that's 80 amps of current at 12 volts. A stock VW generator refunds a max of 30 amps to your battery (360 watts), the after-market alternator conversions are 51 amps (maybe some higher ones avail.). How much heat is 960 watts? A standard drugstore hair dryer uses 1500-1600 watts. And by the way, it has been estimated that a 60 hp engine produces 2700 watts of power as heat.
See? Forget it.
My Experience with Fan Recirculators
[partially excerpted from the end of the BugMods! article]
In spite of my satisfaction with my documented heater improvements, I was always searching for ways to improve it further. The flow of air in the stock system works well when the engine is running at mid-hi revs, but at idle it may be less than adequate, even with my prescribed modifications. I was exploring ways to add electric fans to system to improve air flow. I had been "collecting" squirrel cage fans from Super Beetles for a few years, and had 4-5 of them. I first experimented with putting them under the back seat to "draw" air from the heater boxes when the RPMs were low. But that didn't work as the heat was pretty intense and these fans are made mostly out of plastic. This concept could work (and some parts companies sell such kits) if a metal squirrel cage fan were used and the motor was completely external to the fan and airflow. But be warned, these fans can be very noisy.
There is a company that does something similar with a kit that installs fans on the interior, under the back window and pushes air via hoses into the heater boxes. I didn't like this because:
Did it work? Well, a little.
Stuck in traffic in a snowstorm at idle, with the fans switched on high,
I could feel a small increase in airflow if I put my hand in front of the
hose end. But I took them out after a month or two. Not worth it, in my
About Gas Heaters
Today, I have no experience
with gasoline heaters (I did get one in a '54 that I bought, but only had
it for 2 weeks before somebody came and bought the whole car, heater and
all, from me). For those that don't know, VW installed gas heaters in some
cars. I'm pretty sure it was a dealer option. Two manufacturers that I
know were used are Stewart-Warner and Eberspracher (sp?). And I am told
that there is one place in the US that repairs/restores them. Those who
use them swear by them. Instant heat, don't even need the engine running.
But make sure you know what you are doing or consult with someone who does
if you play around with one. They
can be very dangerous.
Some of this borders on blasphemy of my "vintage" preachings. Namely, cutting a big hole under the dash. Please don't do that to a, say, '67 or older Beetle. If you do, don't tell me about it. The removal of the ducting under the back seat? Well that's not so bad. That could be replaced pretty easily. But I felt it valid to offer this because many people use Beetles year round as daily drivers.
So try those steps if you are
so inclined. Get the hood seal tight, and do the floppy 2 3/4" hose thing.
You know, one benefit of an aircooled is that the heat exchanger (heater
box) begins producing heat almost immediately since the manifolds heat
up after just seconds of running. Not true for a water cooled. I'm sure
if you take my suggestions a wear a sweater you'll be all right. I used
to drive into New Hampshire or Vermont in my '68 to ski when the high for
the day was a single digit, and always got second looks from passing drivers
who once owned a Beetle who seem amazed that I was not wearing a coat,
mittens and ear muffs.
Copyright© 1997; John S. Henry