Block off Plate in Front Heater

[Wildthings]

I have no idea what the block off plates in the front heater assembly are for. Are they in all water cooled Vanagon front heater boxes or just ones sold in more southerly climes? I just left mine out and haven't driven the van yet so I don't know what difference it will make. What have others done?

[Witless Joe]

You mean the ones that swing freely, and have no cable connection to them?

They slam shut when you turn the blower motor on, increasing the air pressure through the system under the influence of the blower. When they work properly, you should hear them slam close as soon as you crank on the blower motor.

If you turn the blower off, they swing open, and allow "ram air" from the front grille to pass through the airbox and heater core when the vehicle is moving.

If they're not there at all, then you'll have lousy air pressure through the vents when you're using the blower motor. But air pressure under the influence of "ram air" when the vehicle is moving, will be unaffected.

[Wildthings]

No I am talking about the aluminum plate that lays tight against the heater core and blocks about 1/2 of its area to air flow.

[ak_runner]

When I had my heater out last Fall I thought about this, the plate does look at first glance like it does more harm than good. I checked with one of my local, and very knowledgeable, Vanagon repair shop/clients of mine and they said to leave it in. That without it the heater output is even worse. Hard to believe it could be much worse than it is, I drive around with condensation or ice on the insides of my windows, and it takes a long time for the interior to warm up. This even after I have improved the system by blocking off the outside air intake and adding recirculating air. You would think that with Germany being a cold climate country that they would have designed a better cabin heating system.

[Wildthings]

I guess that I will know tomorrow whether it hurt or helped to have pulled it out. I know it was damn cold driving through Wyoming and Colorado a month back with only the front heater working.

Couldn't hardly keep my hands warm, reminded me of driving an air cooled.

[danfromsyr]

on my 1980 conversion I left that plate out.. I have VERY good heat (underway) in my TD
but I also added pipe wrap insulaton to my heatercore lines to retain all heat to the front.

on Mom's 86 theres no insulation and it runs cooler then my 80.

also an item to check is the heater control valve. make sure it goes thru full range of motion.
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[Wildthings]

Finally got every thing reinstalled and took the van for a ride yesterday. I couldn't notice any difference in the heat output with the plate having been removed. Not particularly cold out, temperature was just at freezing. I think the heater will be pretty marginal once the temperatures get down to 15°F or so like it was before. I do think that I am getting noticeably more air flow to the defroster ducts than before, but this could be for several reason, like the fins not being clogged with debris and the fan motor working better.

[r39o]

Ya know, I hate to think we are smarter than the VW engineers. VW does not put things in for no reason. That plate is there for some (probably really good and solid engineering) reason. OK, we rebuild the various sub assemblies for ease of use or simply to clean 20 years of abuse and funk out, but to remove some baffle or whatever with out completely understanding what it is there for is not right, at least in my book.
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[Wildthings]

[Volksaholic]

I'm with r39o, although I asked the same question when I was doing a heater rebuild on my '85 a little over a year ago. Nobody seemed to know what it was there for. I don't know enough about thermodynamics and heater design to guess why it's there... it seems kinda goofy to me. By the same token, I don't like to second-guess the engineers without a good functional understanding of what the thing is supposed to do so I left it in.

The heater kicked ass in the '85 when I was done, and the heater in my '88 has been defrosting and heating the cabin nicely, so I figure I'll leave the '88's in as well when I get around to rebuilding the heater box.

One guess I have is that more air can flow through the heater core with the baffle removed, but it may cool down the heater core more than is optimal. If that's the reason, though, why didn't VW build a smaller heater box or at least use a smaller heater core? Maybe the heater core they spec'd was a standard part? Whatever... like I said, it seems kinda goofy but unless someone can give me a plausible reason it's there I'm not going to second-guess.
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1988 Wolfsburg Edition, 2001 Subaru EJ251

[Dogpilot]

I suspect the plate was there for good reason. Given the Van was designed in Germany, intended to marketed there, they probably had something in mind. Germany, from the winters I spent there, is not exactly what I would call 'Tropical'. If your heater is anemic, then I would suspect it is clogged with deposits. No, not interest bearing IRA type, but the same ones that eventually make your radiator not do the radiator thing.

A new radiator core will most likely give you a lot more heat than a 25 year old one. You may want to re-activate the rear one as well. It really will heat you out of the van, at least mine does. The difference between a new and old one is quite dramatic.
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[Wildthings]

No one has stated that German models had the plates, the Bentley doesn't show them, which implies they did not. As I asked in my first post were the block off plates used in all climates or just southern ones?

No doubt the rear heater makes a difference, but since it sits way in the back and is as often as not blocked off by luggage or cargo it often borders on worthless. I have been thinking of trying to reinstall it in the spare battery compartment under the back of the drivers seat. It should not be blocked very often if installed there.

[Volksaholic]

I make a point of not directly blocking the rear heater as it's a main source of cabin heat since it's recirculated air. It's also the primary source of heat for the kid to warm their feet and dry their snowboard boots after a trip to the mountains.

That would be an interesting mod to move that heater up front... it would be more like the auxiliary heat in the Eurovan, only the EV has it on the right side behind the front passenger seat. If I were stacking stuff in front of it I would probably just consider building a little grate that protrudes from the front of the heater a couple of inches. I think that would keep things far enough from the front of the heater to allow the warm air to flow out.
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1988 Wolfsburg Edition, 2001 Subaru EJ251

[Terry Kay]

It sure sounds like the front heater core has given up the ghost.

I'd leave any door's that were installed from the factory in that heater box, and replace what more than likely was wrong with the 20 plus year old Van's heater--the core.

There was no difference in a southern sold Vanagon and a northern one--unless is was specificly ordered different.

The heater boxes are all the same.

If your looking for heat to blow outa the rear heater, I'd think I'd make it a point to keep the area in front of the heater clear.

You wouldn't stack garbage over your home heater vents, and then wonder why the house was cold----would ya?
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T.K.

[Alan Brase]

[Volksaholic]

I kinda like the Toyota air-balance lever so you can dial in how much outside vs. recirculated air you want in the heater system. My Subaru just has a recirculate button that is disabled when the defrost is on. In my Camry I would run in recirculate mode until I started fogging the windows and then start adding fresh air. I think it heated up a little faster when I did that.

I do pretty much the same thing in the Vanagon, only the balance is between the front and rear heaters. The front fan goes on low with the flaps set to defrost while the rear heater (recirculated air) is on 1 or 2 while the van warms up. When the temp needle comes up a little I crank the rear heat until I start getting fog on the windshield and front door windows from the passengers breathing. Then I start really cranking up the front heater/defroster to clear the fog. By then I've got a rolling sauna... it gets quite toasty even with temperatures in the single digits. It's quite a pleasant change from being able to get the defrosters to work and a little bit of finger warmth in my old Splitty busses and air cooled bugs!
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1988 Wolfsburg Edition, 2001 Subaru EJ251

[Wildthings]

The front heater core is clean, I actually swapped it with a known good one while I had it out, no change. I also tested both cores by alternately running hot and cold water through them, the flow rate was good and the temperature change across the face of the cores was even and quick. No I would not consider removing any doors or flaps from the heater box, but a plate that effectively blocks over 1/2 or more of the face area of the heater I would consider removing. No one has of yet postulated any good reason for it being in there except that Germans put it there, but of course those Germans may have been accountants and not engineers.

Removing the plate seems to have made no difference in the temperature of the air stream, but it does seem to have allowed additional air passage when the fan it on high.

As for unblocking the rear heater. No use owning the van if I can't use if for the purposes for which it was bought which was to haul stuff. If my transportation needs could have been met with a Jetta or other small car, I would have bought one.

I am actually going to go into and lube the front blower motor on my 91 either today or tomorrow. Maybe I will do some further experimenting with that vehicle's heat. It has run without its rear heater for at least 1/3 of its life do to a variety of leaks and burned out motors, but since it seldom leaves the warmer parts of the Pacific Northwest heat has never been much of an issue.

[Terry Kay]

<< No one has of yet postulated any good reason for it being in there except that Germans put it there, but of course those Germans may have been accountants and not engineers.>>

Hence the non postulation of why many things the Vangons lacks, need's, and the way it be---
It's just the way the goofy Krauts deciced to make the underpowered, overweight beast's--
Now you wanna know why nobody has questioned the heater box mechanisim's, and why what & how.

First locate the goof that buried the heater box sandwich tight under the dash--then you'd be geting somewhere--


<<Removing the plate seems to have made no difference in the temperature of the air stream, but it does seem to have allowed additional air passage when the fan it on high.>>

What about the other 2 speed's?


<<As for unblocking the rear heater. No use owning the van if I can't use if for the purposes for which it was bought which was to haul stuff. >>

Right.

This is a similar statement made by a guy that I ran into who owned a Vanagon that couldn't get his winsheild cleared up durring the winter.

The dash defroster vent's were covered with misc. whatnot--a bunch of crap.

When I told him that if he got the garbage off of the dash he just might be able to see where he was going--
" What the hell, If I can't keep what I need right now where I can get to it, I'll drive without the defroster's"

Real Smart Guy.
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T.K.

[Wildthings]

Before I tore into my 91 to change the heater motor, I decided to do a little test. As the 91 heater box has never been apart and is 100% factory I took it for a cruise down the road to see what temperature I would measure at the defroster duct.

Conditions:

Temperature valve fully open.
Defrost valve fully open, all others closed
Ambient 40°F
Engine at full operating temperature
Fan off
Needle style meat thermometer stuck into the left defrost vent.

I recorded the temperatures at both 60 & 40 MPH.

Results:

60 MPH - 130°F
40MPH - 144°F

I then repeated the test with my '84 with the plate removed, on the same identical section of highway and the same control settings.

60 MPH - 138°F
40 MPH - 148°F

As you can see the temperature of the air flow at the defrost duct was 8°F higher at 60 MPH for the '84 with the plate removed than on the stock 91, and 4°F higher at 40 MPH. I did not make any attempt to measure and record the inlet and outlet water temperatures, though that would have been very pertinent.

I later pulled down the heater box on the 91 and found the heater core to be clean and will reuse it. In studying the design of the heater box a little more I think VW was trying to even out the air flow density over the width of the heater core by adding the restrictor plate. I personally think that they overdid it and caused a large section of the core behind the plate to have minimal air flow. I think that I will drill a large number of additional holes in the restrictor plate for the 91 and see if I can increase the heat output.

[Alan Brase]

That is interesting data. The other variable you did not control is how plugged with scale the inside of the heater core is.
On old time American cars, the header tanks could be unsoldered and the tubes cleaned out. (I used to spend some time at my friend's radiator shop watching him do it.)
But now all this stuff is regarded to be throw away. I guess you could put a brand new core in both, then measure the results.
But I liked how you pretty much controlled the possible air flow differences created by the fan by simply not using it, but rather controlling the vehicle speed.
Well done.
See if you can get a uni- bit (electrician's step bit) and drill a series of big holes in the baffle.
Al
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Al Brase
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