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Old 04-01-2014, 08:18 PM   #1
JustPassinThru
 
Drives: No more Yaris
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Cutting off Heater Core

Not sure where this goes. If the mods want it elsewhere, feel free to move it.

I'm thinking of putting a valve on the heater hoses - to cut off the flow to them in hot weather. Why? Some residual heat comes out the fresh-air vent system, even when it's on full-cold. Any temperature over 60, the air is too warm - even at night, no UV rays through the acre of glass.

I have air conditioning in the car, but it's silly to use it when it's jacket-weather outside. It uses gasoline; and gasoline costs.

The problem is this: SOME engines, some brands, NEED the heater-hose flow channel to circulate warming coolant - else the coolant in the water jackets boils while the coolant at the thermostat is still too cool to open it up. Some are designed expecting that flow; and some are not.

Which one is the Yaris engine?

If I do this, would a simple watercock (as Nissan/Datsun used to use with its heater on early trucks) do; or would I need to put on a Y-gate valve? Or re-route the heater hoses? I'd rather not get too-much into it; since it's a 2012 and still under warranty.
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Old 04-01-2014, 08:46 PM   #2
CTScott
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Not a horrible idea, as only a little flap of plastic separates the A/C from the heater core when you are in full cold mode.

I have not seen any documentation that definitively shows if the heater core flow can be valved or if the flow is critical. There is a definite positive flow through the core (as opposed to just a radiant diffusion), so I would think that the flow is necessary.

The simplest/cheapest bypass method for maintaining flow would be a pair of 3-way bypass valves with a piece of hose tying the two bypass positions together. This type of PEX RV valve runs under $10 each and is rated for hot water:

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Old 04-01-2014, 09:10 PM   #3
JustPassinThru
 
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That's a good link - http://www.dyersonline.com/bestpex-e...ass-valve.html.

I think I'll give it a try. Here in a new area, in the Bitterroot Mountains, the nights are cold but spring days get warm. Today was one of the pleasing ones...62 degrees and sunny. And the inside of the car was HOT.

And the fresh air, as I expected, was too warm. At Montana's 75-mph speed limits, driving with a window open isn't really practical (I had to travel 120 miles). So it was A/C time, even though I was climbing some steep grades on US 12.

The bypass should end that. When I get a round tuit,



...I'll do a write-up and let everyone know how it works.
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Old 04-02-2014, 04:34 PM   #4
nookandcrannycar
 
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Quote:
Originally Posted by JustPassinThru View Post
That's a good link - http://www.dyersonline.com/bestpex-e...ass-valve.html.

I think I'll give it a try. Here in a new area, in the Bitterroot Mountains, the nights are cold but spring days get warm. Today was one of the pleasing ones...62 degrees and sunny. And the inside of the car was HOT.

And the fresh air, as I expected, was too warm. At Montana's 75-mph speed limits, driving with a window open isn't really practical (I had to travel 120 miles). So it was A/C time, even though I was climbing some steep grades on US 12.

The bypass should end that. When I get a round tuit,



...I'll do a write-up and let everyone know how it works.
Love the picture of the ROUND TUIT! My grandparents had one on their refrigerator the whole time I was growing up. I think my grandmother put it their just to make people chuckle and feel at ease.
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Old 01-19-2015, 07:59 PM   #5
spookybathtub
 
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Did you ever try this? I would love to know about your results, since this heating problem has always bugged me.
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Old 01-19-2015, 09:28 PM   #6
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Would the two 3-way valves go under the hood next to where the hoses enter the firewall, as shown in this photo? The valve linked earlier in this thread is a 1/2" fitting, but I measured the pipe where the hose attaches at 5/8" OD.

What about somehow reinforcing the air mix "door instead to block out heat? Would that be feasible without removing the whole air conditioner assembly?
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Last edited by spookybathtub; 01-19-2015 at 11:00 PM.
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Old 01-20-2015, 04:49 AM   #7
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Looks like they make a product for exactly this purpose. But it's actuated by a vacuum line. I don't understand that, since the whole point of this mod is to have manual control over when the heater is activated.
http://www.autozone.com/climate-cont...-valve/223857/

This cable-operated one might be a good fit:
http://www.oldairproducts.com/catalo...e-p-18658.html
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Old 01-20-2015, 05:15 AM   #8
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I found this diagram in a whitepaper on the 1NZ-FE engine. I'm no expert, but this looks like the heater outflow could be closed with a simple valve — no bypass necessary.
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Old 01-20-2015, 03:05 PM   #9
CoryM
 
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I definitely would NOT block off the heater hoses. You will want to bypass instead. A lot of the coolant flow of the head passes through the heater hose, and you may get hot-spots if you block it off. The heater shut-off valves work well so would be the best bet. The ones linked to by Spooky should be the right size even (the vacuum controlled one is because the OE vehicles have vacuum controlled HVAC systems).
Cheers.
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