[Vwdiesel] VW Tank heater

[Lee Hillsgrove]

>I read from Lee I think that he installed a 1500W tank heater.  Would
anyone
>know where to make the proper coolant line connections for correct
operation?
>What is the directiopn of coolant flow? for a 1981 Jetta or rabbit?




  Here's a reprint from my archives of a post I made to the list on Jan. 24,
2000. Hope it helps. Ask again if it doesn't.  :-))  I think I still have
some poor quality photos I took of the installation if you'd like them, too.

  Lee
  Oo-v-oO
  PP-ASEL
  KB1GNI





  Hi group,
I can start out by saying that we won't have to worry about any more below
zero weather in the Northeast. I can say this because I finally installed a
block heater in my '86 1.6 na Jetta on Sunday. Had to do something about the
no-starts due to the cold.  Now that I have it in, I'll be willing to bet
that the subzero weather has past.  :-))

(installation instructions / observations follow. Skip it if doesn't
concern you.)

I ended up installing a 1500 watt circulation style heater, probably the
same as Dominique's. I wanted to use an 850 watt unit I had, but because of
packaging, the larger one fit better. The 850 was a straight-through, while
the 1500 had the inlet and outlet at 90 degrees to each other. I teed into
the hose leading up to the expansion tank as close to the steel return line
as possible for the supply to the heater, using a plastic Y connector
supplied with the heater, with the Y pointing towards the ground. To this I
attached about 18-24" of 5/8" heater hose which was clamped to the inlet of
the heater. The heater sits very low, between the starter and the battery.
It is not so low as to hang below the bumper or lower apron, though. This is
the main reason I couldn't use the 850 watt unit, it hung down too low.
Coming out of the top of the heater is about 6-8" of 5/8" hose. from this
point on, I used 1/2" and 3/4" copper tubing to splice together the hoses
and create adapters and tees. The outlet from the heater attaches to a 1/2
to 3/4 adapter, which is connected to a 3/4 tee. One side of the tee
continues straight ahead into the molded hose from the right side of the
cylinder head. I cut this hose off after the first 90 degree bend which also
reduces from 1" to 3/4" and turned it so that it was facing the front of the
car. The branch from the 3/4 copper tee is facing down towards the
transaxle. There is then immediately an ell facing toward the firewall. This
is connected to the remainder of the old hose which used to go from the head
to the heater core. It is routed low, over the transaxle, and bends up
before the shift linkage. At this point it is spliced with a section of 3/4
copper tubing to another molded hose, the same as the short one that
connects the other side of the heater core to the steel return line. I got
this hose from my parts car. This is naturally bent just so that it clears
the rest of the obstacles and hooks up to the heater core. I did not touch
any other hoses or lines.

In operation, the heater sucks cold coolant from the steel return line that
goes to the water pump. Hot coolant exits the top of the heater, into the
copper tee, straight through into the head, where it cools and sinks to the
bottom of the block where the water pump is, thus completing the
thermosyphon cycle. No hot coolant seems to go into the heater core since it
would have to flow downhill. It is a gradual rise into the side of the head,
so that is the path the coolant takes. Once the engine is started, the flow
tries to reverse, with coolant being pumped out of the head. The flow hits
the 3/4 copper tee and is blocked from entering the heater by the check
valves. The coolant is thus pumped into the downward-pointing branch of the
tee and then into the heater core. At this point, the heater has to be
unplugged since the check valves in the heater prevent reverse flow and it
would overheat. These check valves also prevent the coolant from bypassing
the heater core. Heater action seems to be unaffected by this modification.

Since it was only +12 deg. F this morning, I can't say for sure how well it
will work in subzero weather. I plugged it in for only 15 minutes before
leaving, however, and it was warm enough so that the glow plugs wouldn't
even come on, although the block hadn't heated up thoroughly yet. The
temperature sensor for the glow plugs is on the fitting on the side of the
head that the hot coolant enters when the block heater is on. Because of
this, I had to crank a little longer than I should have, but it fired up
after maybe 5 or 10 seconds. Tomorrow I will try 1/2 hour. The timer I had
bought for turning the heater on is only good for 900 watts, so I need to
manually plug it in before I leave for work. Maybe I'll look at a heavy-duty
relay fired by the timer later.

Installation took about half the day, give or take. If I had to do another
it would take about half the time since I know what I'd be doing now. I'd
like to see Dominique's installation to compare with what I came up with.
Hope this helps someone else.