Heater Valve
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Heater Valve
Hey all -
I've searched all over and can't seem to find an answer to this basic question. I recently replaced my blower motor on my 73' with factory a/c and the problem is that I've only had the truck for two months (the blower was not working when i purchased), on top of that, the last time I drove a 73' was never so i'm in a whole new world here.
I re-checked everything and the vacuum lines to the heater heater valve, in/out lines to heater core, and mixer under the hood all 'check out' as put back together correctly.
Here's the issue, I get heat, the cab warms up but it's "warm" not HOT air. If I had to guess, I'd say it's in the mid 70's coming out of the floor vent with the mixer lever set to warm (all the way to the right).
So, I'm thinking I may have a problem with heater valve but wondering if it's just how the truck heats the cab and I don't want to spend $80 or so on a new heater valve plus dealing with draining the rad. etc., etc. if the end result is the same.
I've searched all over and can't seem to find an answer to this basic question. I recently replaced my blower motor on my 73' with factory a/c and the problem is that I've only had the truck for two months (the blower was not working when i purchased), on top of that, the last time I drove a 73' was never so i'm in a whole new world here.
I re-checked everything and the vacuum lines to the heater heater valve, in/out lines to heater core, and mixer under the hood all 'check out' as put back together correctly.
Here's the issue, I get heat, the cab warms up but it's "warm" not HOT air. If I had to guess, I'd say it's in the mid 70's coming out of the floor vent with the mixer lever set to warm (all the way to the right).
So, I'm thinking I may have a problem with heater valve but wondering if it's just how the truck heats the cab and I don't want to spend $80 or so on a new heater valve plus dealing with draining the rad. etc., etc. if the end result is the same.
Cargo Master
Joined: Nov 2009
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From: starship enterprise
Well, what I do is feel both heater hoses with the heater valve on, fan off, again with fan on, heater valve on, again with heater valve off. See if you can feela difference in temp. It is best to do this in sequence with engine warm so that you feel heat if it is there. What I mean by this is turn heater valve off, leave off till engine is warm, feel hoses, they should be cold, then turn heater valve on the hoses should be warm, both about the same, then turn fan on high, feel them again, mine will have one hot one and one barely warm from the heat exchange from the heater core.
Another thing that has happened is the coolant level will drop low enough the you will have no heat due to no coolant coming from the engine.
Is your engine coming up it temp? It might be a cold engine it might also be a bad heater core. FUn fuN
Another thing that has happened is the coolant level will drop low enough the you will have no heat due to no coolant coming from the engine.
Is your engine coming up it temp? It might be a cold engine it might also be a bad heater core. FUn fuN
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Ahhhh. Ok, the test makes sense, I check that. Yes, the engine seems be getting to correct temperature and maintaining. The gauge reads just to the left of center and doesn't move. I understand the gauge can could be bad but the engine seems to be getting to the correct running temp. I refilled with anti-freeze and it's visible when looking in the rad. after the blower replacement.
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Yes, sir. Per my 1973 ford tech. manual and a second quality assurance check of my handy work, everything has been reconnected correctly.
Fleet Owner
Joined: Dec 2009
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From: NorCal
Excellent! I for one am finally glad to hear someone actually uses a manual. You'd wouldn't believe how many in here fly by the seat of their pants (or unable to help themselves!). But I digress...
Cargo Master
Joined: Nov 2009
Posts: 2,364
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From: starship enterprise
The engine temp on the guage really is irrelevant. If the heater hoses are as hot as the top hose then you have coolant circulation.
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Ford Parts Specialist
Joined: Nov 2006
Posts: 88,826
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From: Simi Valley, CA
1973 F100 with factory installed integral A/C
Originally Posted by Bmoon1492
So, I'm thinking I may have a problem with the POS heater water valve and don't want to spend $80 
or so for it.
or so for it.D4AZ-18495-A .. Vacuum Controlled Heater Water Valve (Motorcraft YG-136) / Available from Ford / It ain't 80 bucks unless you're buying it from Ben Dover Auto Parts.
MSRP: $34.46 // FTE Ford Dealer Parts Dept sponsor tousleyfordparts.com price: $18.95
This valve is a notorious POS! Gets stuck closed, open or partially open.
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Post Fiend
Joined: Dec 2007
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From: Lost
Also, the temp control slider operates a blend door, check to see if the door is opening/closing correctly. The door's lever is in plain sight on top of the heater/ac box, under the hood.
Hotshot
Joined: Apr 2009
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From: Stanley, VA
Ford Parts Specialist
Joined: Nov 2006
Posts: 88,826
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From: Simi Valley, CA
Very true. Easy way to see if the valve is stuck partially open, is look at the lever that the rod attaches to. If that lever is not fully against one of the "stops," grab some pliers and see if you can move the lever.
Also, the temp control slider* operates four blend door motors, check to see if the doors are opening/closing correctly.
Also, the temp control slider* operates four blend door motors, check to see if the doors are opening/closing correctly.
Bolted to the backside of the A/C/heater control panel is this little charmer:
*D5TZ-19B888-A .. A/C Vacuum Control Selector Valve Assy ~ Includes "kicker switch" for A/C. All the vacuum lines from the blend door motors, POS heater water valve connect to it.
When you slide the lever on the control panel, this valve opens one blend door, closes another.
With factory A/C, there's a mind boggling plethora of heater/A/C related parts behind the dash.
A/C or heater no workee: Could be a cracked vacuum hose and/or defective blend door motor, and/or the POS heater water valve, and/or the selector valve has crapped the bed.
Post Fiend
Joined: Dec 2007
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From: Lost
Blend door vacuum motors: D3TZ-18A318-A .. A/C-Heat Door / D3TZ-18A318-B .. Heat-Defroster Door / 1973/76 only: (2) D3TZ-18A318-C .. Outside Air Door & Recirculating Door.
Bolted to the backside of the A/C/heater control panel is this little charmer:
*D5TZ-19B888-A .. A/C Vacuum Control Selector Valve Assy ~ Includes "kicker switch" for A/C. All the vacuum lines from the blend door motors, POS heater water valve connect to it.
When you slide the lever on the control panel, this valve opens one blend door, closes another.
With factory A/C, there's a mind boggling plethora of heater/A/C related parts behind the dash.
A/C or heater no workee: Could be a cracked vacuum hose and/or defective blend door motor, and/or the POS heater water valve, and/or the selector valve has crapped the bed.
Bolted to the backside of the A/C/heater control panel is this little charmer:
*D5TZ-19B888-A .. A/C Vacuum Control Selector Valve Assy ~ Includes "kicker switch" for A/C. All the vacuum lines from the blend door motors, POS heater water valve connect to it.
When you slide the lever on the control panel, this valve opens one blend door, closes another.
With factory A/C, there's a mind boggling plethora of heater/A/C related parts behind the dash.
A/C or heater no workee: Could be a cracked vacuum hose and/or defective blend door motor, and/or the POS heater water valve, and/or the selector valve has crapped the bed.
I came up with D3TZ-18518-A, but I don't know how accurate it is, as it came from a repro co. catalog......
Ford Parts Specialist
Joined: Nov 2006
Posts: 88,826
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From: Simi Valley, CA
Same pic in the '73/79 Ford car parts (Bronco) catalog: Illustration Section 195.1, Page 34.
I see vacuum nipples on two of the motors, one is turned around, so all I can see is its backside.
No cable is shown in either pic, but you're right, one is listed.
All the part numbers I've typed in this thread are from memory, didn't need to look them up.
The POS heater valve also used in 1971/90's cars (D4AZ-A replaced D1AZ-A) and 1975/2001 (prolly later) Econolines.
Hotshot
Joined: Apr 2009
Posts: 14,333
Likes: 247
From: Stanley, VA
Here's pg 18. Also, there is a cable on the factory (integral) A/C. It goes from the temp control lever to the blend door in the evaporator housing that's in the engine compartment.
Ford Parts Specialist
Joined: Nov 2006
Posts: 88,826
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From: Simi Valley, CA
Otherwise, I'd have to get up off my backside, walk around the table, stepping over 5 Basset Hounds in the process, to the microfiche viewer.
Insert slide 2 of 10/88 edition, turn viewer on, hope the bulb doesn't blow, cuz it's 25 bucks and not that EZ to find.