The good old Eberspacers again...

raygreenwood · Post by **raygreenwood** » Sun Mar 01, 2009 2:16 pm

In gneral, the 411/412 stock heater boxes will keep you warm at speeds of 45 mph and up....when the outside temp is about 40 degrees or higher. I have done the heater boxes with extar inline fans before. That nets you about 5 degrees of ambient ability....or the ability to stay reasonably warm at 45 mph or over...with external temps at about 35F...thats all.

the problem is not the distance from the heat exchangers to the car and air volume. The problem is that in order to keep the air hot.....until it comes out the vents, its necessary to get an awful lot of metal hot and keep it that way...in the body heater channels.

The problem over a certain fan speed no longer becomes an air volume problem..it become a problem that the air spends so little time in the heat exchanger and that exchanger has so little surface volume, that it cannot get the air hot enough to have it be able to lose a significant amount of heat to the body heater channels...and stikll be usfully warm. The gas heater on the other hand...has a huge volume of surface area...and gets much hotter. The air coming from the gas heater...can easily hit 200F at its exit from the heater. It will lose 50F or more in the heater channels. I have measured 150F at highway speeds at my heater vents.

I would keep the gas heater. Its just not very difficult to work on....and works so very well. Ray

wildthings · Post by **wildthings** » Sun Mar 01, 2009 5:11 pm

My only actual experience of adding an inline fan is with a bus setup. There the inline fan makes a major difference in the heater outlet temperature. The BTU's available at the heat exchangers is pretty incredible. On a bus if you remove the center pipe at the front of the wye the air flow is totally impressive. The temperatures under load will exceed 230°F on a cold day and the volume is 4 or more times what you would ever see reaching the cab on a stock system. I really want to try a centrifugal inline fan on a bus. I am guessing it would give you heat pretty pretty much equal to anything else on the market except on long downhills.

raygreenwood · Post by **raygreenwood** » Mon Mar 02, 2009 5:09 am

Oh I would totally agree on a bus. lack of volume IS the problem on a bus. Plus...when properly installed....the bus center duct has an insulating jacket does it not? That shoud lhelp a little once the volume is up.
The 411/412 on the other hand....has no real insulation for the heater channels.
I agree that the BTU's are excellent on heater boxes. Its just that the losses just outside of the boxes are huge.
Yes....the real problem is poor insulation of everything south of teh heater boxes in most cases. Ray

MGVWfan · Post by **MGVWfan** » Mon Mar 02, 2009 8:21 am

In my experience with a 412 wagon, a big problem is the convoluted airflow path and relatively low flow from the heater's hot air blower. I can't get enough airflow at idle and low engine speeds to keep the inside warm at any temp below about 45 deg F...and I've tried two different blowers, and multiple duct configs. I think having the blower on one side of the engine compartment causes enough restriction to be a problem. BTW, I dissasembled the exhaust HX's when I did the engine years ago, sandblasted, and repainted, and sealed all the cracks and holes...no leaks...also, all the check flaps are installed and working, also cleaned the mouse nests out of the heater channels

. Above 10 mph, no problem, the engine's blower puts out enough airflow to defrost and heat well down below freezing (with the Eber, of course). I suspect the sedans don't share the wagon's low flow at low rpm's issue, due to the better blower location and duct routing. I'm still experimenting with the blower and ductwork to find a good way to flow more air at low rpm's.

wildthings · Post by **wildthings** » Mon Mar 02, 2009 8:58 am

I have thought about redoing the ducting on at least one side so that it enters the cab at the rear and doesn't run through any convoluted ductwork. I had a '73 Thing years ago with only a gas heater. Added T1 heater boxes to it and duct one under the rear seat and another into the rear deck area. That would easily keep the drafty old thing warm down to 10°F or so. I would only have to run the gas heater to keep the windshield defrosted.

Getting rid of the piping loses is huge.

raygreenwood · Post by **raygreenwood** » Mon Mar 02, 2009 1:50 pm

Yes, the variant has a little more of an issue. That "fork" duct that splits from the blower motor...loses a lot of velocity.
Also, if you do not have them...you must have the insulated duct hoses that go from the gas heater to the body.
If you are using the corrugated plastic hoses from the blower to tthe heat exchangers instead of the foil and paper hoses...you are losing a lot of velocity.

I also found a lot of losses on all models..at the actual floor vents. A huge amount of restriction....that and the fact that the cable from the lever does not actually open and close them all of the way.
Remove the triangular vent down by the base of the seat and remove the flap unit from the body. Check its range of motion with the movement of the up/down heater lever. I have found that most of them do not open the flap very far at all. It can be timkered with and adjusted. I put a spring on that pulled the flap open....so the lever keeps it closed when I shut it...but it springs open all of the way.

Also....just a question: But....at what knob setting are you finding you have to keep the green knob on the dash to get adequate heat?
At 10 below...I did not have to have it over 3/4 of teh total turn availalable. I may turn it up high to get things warm...but generally between about 5F and 30F....1/2 knob turn is all thats needed for heat maintenance.
The culprit was too low of a fuel pump setting. So...you need to perform teh fule pump volume test.
Though the variant gets a little lower air flow....it should still be very hot...like 125-150 at the vent. If its not....then you are not getting enough fuel to produce the heat you need.

The system should cycle. Run for about 3-8 minutes even at 10-20F outside sitting still or in traffic......and be right on the verge of cooking your feet...and then it shuts the fuel pump down and then pumps air for about 2-3 minutes before starting to pump fuel again. If this is not happening and your knob is turned up all th eway...and it seems to run constant and not produce enough heat....you have incorrect fuel settings. Ray

MGVWfan · Post by **MGVWfan** » Mon Mar 02, 2009 2:20 pm

Oh, it's not fuel pump-related...that puppy is adjusted per spec. I've got the OE VW Eber service manual, followed it to the letter. It's working as intended I believe.

The air coming out at idle gets blisteringly hot, but very low volume, and the temp controller cycles frequently at idle...but at speed, it all works as intended, with decent volume, and longer cycles. I do need to look at the floor/defrost flapper, though, good hint there Ray!

FYI, at speed, I keep the t'stat set at about 3 o' clock, anything more clockwise and it gets hot inside.

haz · Post by **haz** » Tue Mar 03, 2009 6:05 am

haven't rea all the replies, but I found this

http://manuals.type4.org/ba4/