Heater control valve installation.

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Mar 20, 2024 | 03:21 PM

rosaliod

Thread Starter

4wd Low

Joined: Oct 2023

Posts: 14

Likes: 2

Heater control valve installation.

79 Ford F-150 Custom
Anyone know which hose the heater control valve should be installed on Left or Right? Does it matter?

Mar 20, 2024 | 04:10 PM

jflem

Tuned

Joined: Jan 2021

Posts: 254

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From: Longview Texas

Both of my trucks have it on the right one.

Mar 20, 2024 | 04:21 PM

rosaliod

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4wd Low

Joined: Oct 2023

Posts: 14

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Thanks for the quick reply. That's what I'll go with then

Mar 20, 2024 | 05:06 PM

tbear853

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Joined: Feb 2004

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From: The Shenandoah Valley

My '77 has always had it on the left hose looking at the heater inlets from the front bumper looking towards the firewall. The hose attached direct to the water pump. Book shows it on the other hose though, maybe mine was moved by the prior owner and I just never knew otherwise?

But I fixed it in the future.... see below

Last edited by tbear853; Nov 7, 2025 at 12:00 PM.

Mar 20, 2024 | 09:38 PM

Rubiranch

Logistics Pro

Joined: Jun 2004

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From: South Central Utah

The heater hose that comes from the intake manifold goes to the right side of the heater core.
The heater core is bottom fed with hot coolant from the intake manifold and that's the hose the control control valve goes in.

Nov 7, 2025 | 12:23 AM

tbear853

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Joined: Feb 2004

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From: The Shenandoah Valley

As I said back then in March 2024, it appears mine has been wrong since I bought the trick. I've always just placed it like it was when I first replaced a heater valve (several) times thinking they were leaking, but they were on the wrong side and heat was finding its way to the core.
Makes sense.
Is an easy thing to change tomorrow though.
So what I want is "fitting near T-stat housing base to heater valve inlet to right side of heater core is hot flow to core .... and left side heater core to water pump fitting is for cooler now coolant returning to the engine.
Glad I have extra hose.
I just need to move the valve over to the other hose then, arrow towards heater core. I don't think the core cares, but my heater valve might.

Nov 7, 2025 | 10:13 AM

beartracks

Lead Driver

Joined: Nov 2000

Posts: 6,628

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From: Albuquerque

Be sure to observe direction on the valve. There is usually a little arrow.

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Nov 7, 2025 | 11:58 AM

tbear853

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Joined: Feb 2004

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From: The Shenandoah Valley

Quote:

Originally Posted by beartracks

Be sure to observe direction on the valve. There is usually a little arrow.

10-04! It is**

I had just assumed it was right when I bought the truck, even when I put the AC in right afterwards, I was particular to put the heater valve on the same hose as relates to the engine. I've put a few replacements on since, always same. The original was mostly metal, I'm not sure it cared. It always seemed that was heat in the core which is why the two ball valves were added, and they were handy even when testing. Was lately while chasing the leak that I again thought about it, and so last night I researched and while I knew of the arrow, for some reason I had it in my head that I needed it in that hose. It is correct now and flow direction matches the arrow**. I was able to move hose pieces and valves and that took longer deciding which / where to get my extra valves placed to suit and not needing more hose.