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914World.com _ 914World Garage _ '74 Heater Layout Question
Posted by: orbit398 Jan 31 2016, 09:37 PM
I have a 2.0 liter and am trying to piece together the heater system. I have most of the pieces but can't seem to find a picture or diagram of how the fan or fans push the air up to the front. My car has a single fan (only one outlet) mounted right by the relay board. With this one fan, it will only push air along the driver side. How does the other side get air? I have seen pics of a splitter that would enable an air duct go across the engine and push air on the passenger side. But my fan only has a single connection. Any ideas or pictures appreciated.
Also, where is the best place to purchase the heater control valve/flap? Or does anyone have good used ones they'd like to sell?
thanks
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Posted by: The Cabinetmaker Jan 31 2016, 09:43 PM
The splitter attaches to the single outlet that you have.
Posted by: rhodyguy Jan 31 2016, 09:47 PM
The splitter connects a longer piece of tubing from the fan and goes to the pass side j tube. No second hose? You HAVE to cap the j tube if you want Hot air that defrosts windows or the hot air spills into the engine compartment and the stench gets in the interior too.
Posted by: orbit398 Jan 31 2016, 10:15 PM
Wonder why my fan only has the single hose connection. Was there was supposed to be a second fan for the other side?
I have seen fans that have two outlets also. Did some cars have those?
thanks - new to the 914 so I am learning
Posted by: Dave_Darling Jan 31 2016, 10:44 PM
70-72 fans had two outlets, one on each side. The fan was mounted to the fan shroud, relatively near the center of the engine.
73-74 cars had the fan moved to the left side engine shelf. The fan had a single outlet, and it was plumbed only to the driver's side J-tube. The passenger's side one was capped with a plastic cap.
75-76 cars had the same fan and same location, but there was a splitter on the outlet. One hose ran to the driver's side J-tube, and a longer one ran across to the passenger's side one.
In all cases, the engine's cooling fan was also piped into the heat exchangers. So even when the heater blower wasn't running, air was going through them. The blower was only supposed to run when you pulled the heater lever all the way up; pulling it a lesser amount only opened up the "flapper valves" so the engine cooling fan could push warmed air into the car instead of dumping it under the car. That's why the heater blower is sometimes called the "auxiliary heater fan".
--DD
Posted by: rhodyguy Jan 31 2016, 10:46 PM
Use the fan that seems to run best. Use a battery to test them. Is all of your other ducting in place?
Posted by: orbit398 Feb 1 2016, 08:24 AM
70-72 fans had two outlets, one on each side. The fan was mounted to the fan shroud, relatively near the center of the engine.
73-74 cars had the fan moved to the left side engine shelf. The fan had a single outlet, and it was plumbed only to the driver's side J-tube. The passenger's side one was capped with a plastic cap.
75-76 cars had the same fan and same location, but there was a splitter on the outlet. One hose ran to the driver's side J-tube, and a longer one ran across to the passenger's side one.
In all cases, the engine's cooling fan was also piped into the heat exchangers. So even when the heater blower wasn't running, air was going through them. The blower was only supposed to run when you pulled the heater lever all the way up; pulling it a lesser amount only opened up the "flapper valves" so the engine cooling fan could push warmed air into the car instead of dumping it under the car. That's why the heater blower is sometimes called the "auxiliary heater fan".
--DD
Wow - thanks for the detail. Exactly what I was looking for. thank you.
Posted by: orbit398 Feb 1 2016, 08:29 AM
Use the fan that seems to run best. Use a battery to test them. Is all of your other ducting in place?
Most of it is. Need the flex tube and the heater control valves/flappers. These control valves are very pricey. Any suggestions or perhaps some volkswagen can substitute that is less costly?
Posted by: rhodyguy Feb 1 2016, 08:41 AM
Used, serviceable sets of valves can be had at a reasonable cost. Post a wtb and be picky. I imagine you will receive multiple offers. When you have all the items installed you're going to be surprised at level of hot air delivery. Even with no aux fan and the j tubes capped.
Posted by: BeatNavy Feb 1 2016, 08:49 AM
be picky.
These flapper boxes take a beating with the heat that runs through them, and the valves tend to wear out. If you want heat when you want it (and only when you want it), consider getting new ones or make sure you get truly serviceable used ones.
Posted by: rhodyguy Feb 1 2016, 09:02 AM
Slight hot air leakage might be the case due to spent sealing material on the valve doors. Not that big of a deal. Leakage can be cooled down by mixing hot with cooler outside air using the dash controls. Take the top off.
Posted by: BeatNavy Feb 1 2016, 09:05 AM
Kevin (or anyone else), what would you use to cap off the J-tubes? I'm dealing with an issue now where my head temps seem to really go up when I have the heater valves open and I want to just try capping those off to see what happens. Sorry for the slight highjack, but it's probably relevant to the OP's question.
Posted by: rhodyguy Feb 1 2016, 09:27 AM
2" rubber pipe caps (perfect fit) and a couple of stainless clamps from the plumbing department at your hardware store. to be fancy the large stock air hose clamps will work too. mongo say cheap good.
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