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Beware the heater control valve

Frankensteineken

NAXJA Forum User
Location
MN
So I changed my radiator the other day, and decided it might be a good time to flush the cooling system. I took the heater hose off the thermostat housing, and was trying to get my garden hose up to it, and before I knew it, the heater hose was in my hand, attached to nothing. After a quick look, I found the heater control valve brittle and rotten, and was falling apart. I could crumble the entire thing in my hands.

Good timing for it to fail in my garage. But, I was surprised at the poor condition it was in, even after regular coolant changes and maintenance. Beware of the plastic!

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Looks like my factory radiator with plastic tanks. Long gone behind the garage now.

The heater valve does help prevent the earlier models having a/c loss of efficiency. Blocking hot coolant from the core eliminates a heat source the a/c would have to overcome.

If the later models eliminated it, I suspect the HVAC box was seriously redesigned to prevent air mixtures, and that's why the valve was dropped. I wouldn't dump it until you thoroughly research and understand why. Lots of off the cuff mods get recommended like this with no thought of the unintended consequences.
 
There have been many posts of people who eliminated it who specifically reported no loss of AC. It is logical that you are running more heat into the passenger compartment, but we have documentary evidence that this is not a problem. In searching for this, you will find MANY people who converted from the closed to open system who did this.
 
If the later models eliminated it, I suspect the HVAC box was seriously redesigned to prevent air mixtures, and that's why the valve was dropped. I wouldn't dump it until you thoroughly research and understand why. Lots of off the cuff mods get recommended like this with no thought of the unintended consequences.

I looked at the FSM and the airbox design. With the blend door moved over to cool, the door blocks all air flow through the heater core. I saw no change in the air temp on the cool setting after eliminating the valve on my 89.

I did this as part of converting to the "open" radiator setup and flushed the heater core at the same time. I got tons of crap out of the core and the heat (when i wanted it) was incredible after that.

If you eliminate the valve, beware that one of the nipples on the heater core is bigger so you'll either have to adapt the hose or pre-stretch the end of the hose to fit (what I did). Don't forget to cap the vacumn line to the valve.
 
Eliminating this valve?

This is the first I have heard of this. What's the purpose? Aside from ditching an annoying, easy to break part?

Exactly. In my case, I didn't bother buying the new style when I converted. Plus the old one self destructed when I looked at it funny.
 
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