My heater blower has been changed to 12v. Not sure what was used, but it does not put out much air and the defrosters are very slow in working. They put a toggle switch in the control panel below the dash. Is there a way to tell if it is one or 2 speed? Will a 2 speed switch for 56 f100 work on my application? Does anyone have a diagram on how the hoses are hooked up to the temp control valve and the heater core? Right now the hoses are hooked straigth to the heater core bypassing the control valve on the firewall. I would like to hook it up correctly so I can control the temp. My heater set up is the fresh air style.

 

Hi Pappy,

I believe (and I could be wrong here), but I believe that the speed control for your heater motor is a rheostat in the switch itself. If it is two speed the switch has detents for low and high speed. It is a simple contact switch like the headlight switch, and the 56 switch should work fine. The new one on my 51 (12 volt) is a full rheostat and gradually increases as you turn up the ****.

Out of all three of my trucks (51, 55, 56, over time) none of them had a tremendously strong blow from the heater motor.

I have a line drawing from the Parts and Accessories Illustrations Manual I'm going to try and scan and post. Here it is:





Lower hose (from 18599) is hot in from engine, top one (18551) goes to heater inlet.

Hope that helps,

J!

 

Hey J, I am still confused. How is this hooked up to the heater core? The heater blower is 12v with a part number of 14576 C 99. It has two wires, an orange one and a black one. Can you tell me if this is a one speed or two speed motor? Will a switch for a 56 f100 work in place of the toggle switch?

 

It is doubtfull that your heater motor has a two speed winding. Here is a way to tell for sure. Hook the case of the motor to negative and try hooking either one of the two wire leads to positive 12 VDC. If it runs on either one of them or both it is probably a two speed motor. Most likely it won't run that way. If not try using the two wires hooked to the battery. If it runs try it in both ways by changing the polarity. If it does run both ways it may be that you have it hooked up to run backwards. Squirrell cage blowers will still blow out a little air even when going backwards. Another thing to check is the motor bearings. These motors have graphite impregnated bronze sleeve bearings. When they dry out they tend to drag and create a lot of friction which causes the motor to run very slow if at all. Another broblem is that the brushes in the motor could be about gone.

I looked at the Ford schematic wiring diagrams and they don't show heater motor wiring diagrams. I suppose this is because the heater was optional back then.

Most heater motors get their different speeds by using series resistors and a switch. I'm pretty sure they wouldn't use a rheostat in the switch because it would produce a lot of heat and have to be rather large to accommodate a heater motor.

Later Man...

 

Hi Pappy,

Water flow hook up is simple: The water flows from the engine nipple (18599) through the hose to the bypass valve (18495) and out of the bypass valve (hose 18551) to the heater core inlet. The water flows out of the heater core back directly to the engine. 18518 is the "Temp" cable on the dash withthe heater controls.

I didn't explain this very well before, but the 48-50 NOS heater **** I have is a rheostat and turns clockwise to increase the heater motor speed as it turns. A Rheostat of course is a variable resistor. It works the same as the instrumentation lights dimmer on the headlight switch. 51-52 went to the two position pull switch.

On your truck according to the Accessories Manual the Fresh Aire Heaters for 53-56 were the same with the difference being the 56 motor was 12 volt. With the exception of very minor changes (mainly ducting) these were the same set up as the 51-52 Freshe Aire Heater.

The 56 switch is a pull switch that has three positions (the same as a headlight switch) "Off," "Low" and "High." The 56 switch will work fine on your truck as long as you have a 12 Volt system and a 12 Volt Heater Motor.

One of the wires on your motor is for ground (on the inside of the heater cover) the other goes to the heater switch. According to the my Shop Manual (P 287-right next to the heater motor wiring diagram): "Two speeds are provided for the blower fan by means of a switch and a resistance unit mounted on the switch. Blower speed is reduced by the introduction of the resistance in series with the blower motor."

You can test to find which is ground and which is power by touching the leads to the battery and reversing the leads and touching again. The fan should turn such that it sucks from the center and blows out. Which ever lead is on the negative terminal when it turns the right direction is your ground wire.

And yes, compared to todays blowers, they are very wimpy with regard to flow!

J!

 

As Julies mentioned above the heater on my 55 worked the same way it blew really slow even when it was turned to max, I had a white plastic **** that increased the speed of the motor as it was turned clockwise. I just went to Auto Zone and matched the motor with a similiar new one and worked fine.

 

Yep, this is one of the very few areas where you have to be careful what youmix-match when changing from 6 volt to 12 volt. Any place you have resistors or rheostats to drop voltage to an item to dim lights or change speeds, it has to be 1) rated for the right accessory voltage (and thus amperage) and it has to be rated to the power source.

That round **** type heater control is the same as mine and it was used typically onthe 48-50 Magic Aire heaters. I had to install a Vol-ta-Drop to power my heater because I couldn't find a 12 volt motor.

Two things will happen when youuse a 6 volt rated heater switch with a 6 volt heater motor on a 12 volt system: your motor will just creep, and you will burn up youswitch fairly quickly.

On this set up, the 56 switch is the way to go!

J!

 

THanks everyone for the information. This will help. Been over 18 years since I had my first one and I have not worked on any old trucks since then.

 

Hey Julies, I have a 350 chevy in my truck right now. I know that is a sin, but that is what was in it when I bought it and I have other things I want to fix before I get around in swapping in a ford. Which hose would I connect to the bottome of the temp valve, the one coming from the water pump or the one coming off the manifold. Would I then connect the other outlet from the temp valve to the heater core from where I disconnect the hose I move to the bottom?

 

Hey Julies, I have a 350 chevy in my truck right now. I know that is a sin, but that is what was in it when I bought it and I have other things I want to fix before I get around in swapping in a ford. Which hose would I connect to the bottome of the temp valve, the one coming from the water pump or the one coming off the manifold. Would I then connect the other outlet from the temp valve to the heater core from where I disconnect the hose I move to the bottom?

 

Pappys53 sent me an E-mail through the site (my E-mail and PMs are blocked here) and I cannot reply that way.

Here is the picture he was asking me about:



My truck did not have a valve to shut off the water flow to the heater core in the summer. It was HOT in there the first couple of times I drove it in 90+ degree weather before I figured out what was causing it.

Mine is the stock 272 Y-block. The water pump has a built in bypass (extra hose for the water to flow through) if the heater hoses are blocked. You can see the bypass hose if you look between the upper radiator hose and the crossover exhaust pipe in the first pic.

Since I did not have a way to shut the flow off, I went to the parts store (O'reilly auto--in this case) and they let me dig through their books. I looked at the shut off valves for all sorts of vehicles. The one I found that would fit my hoses and could be cable operated was actually for a freightliner (semi truck). They had it on the shelf in the back. I think it was around $10, but my memory is shot (old age).

I installed it inline. The plan was to get one of those lawn mower cables and mount it in the glove box (hidden), but it was never needed. In the late fall when it starts cooling off (about now), I flip it open. When it starts getting hot in the late spring..I close it.

My actual heater core and all that was rebuilt/replaced before I got the truck.



The heater and defrost work OK. They are not as powerful as a newer vehicle. I do have a 2 speed fan as well. My truck was 12V from the factory.

Hope that helps answer your question. If you want further information, just ask.

EDIT: What 56 switch are you talking about Julie? The fan control? Mine is just a pull switch with 2 clicks. One for low and one for high. The other **** has an in and out position for the floor or defrost. I do not have the fancier heater that was available in as another option though. Maybe those were different?

 

Hi Brian,

I was talking about BOTH 48-50 and 51-56 type switches. So if my descriptions weren't clear here it is again:

The heater blower switch for the 48-50 was a **** type that rotated to be turned on from "Off" to "Low" to "High." They were dentented to hold th eswitch in th evarious positions and worked by a rheostat-the same same as your instrument lights dimmer. The aftermarket replacements for those use a rheostat but no detents so it is a "variable speed" set up.

The 51-56 switches were push pull types with 3 positions: "Off," "Low" and "High". it works with a resistor for speed variation.

J!

 

Hmmmmm, a 350 Chebby,,,,a 'Small Block Chebby' SBC....hmmmmm

Well, since I actually have had 3 vehicles with that engine in them (but they were Chebbys - that was before my F1/F-100 days) I guess I'll speak to you!

Ok on the heater, when it's cold outside you want the heater core to heat up with hot coolant as soon as possible. When it's hot outside you don't want the extra heat in the cab that a hot heater core will radiate.

So, you use your bypass valve in hot weather to keep the heater core cool.

But this question has to do with getting that heat to the heater core as soon as possible on those cold days.

Now remember what you are doing is "borrowing" heat from the engine via the coolant. In the first 3 to 5 minutes of engine operation that engine and the coolant in it are cold. So the only way it gets warm is to draw heat off the running engine. Now, the engine thermostat is going to stay closed until the coolant gets hot enough to open it (at about 160 or more degrees).

In the mean time you want that heater to heat up NOW, so you draw the first coolant to get warmed up, and run it through the heater - that's the coolant stuck in the engine until the thermostat opens.

So, (and we need to be sure we use the terms "inlet" and "outlet" here) the coolant needs to flow from the "engine (intake manifold) outlet"; to the "bypass valve inlet" where it is blocked from flowing further (it may be routed out the "bypass to-engine outlet" and returned to the engine - depending on the type of valve) OR, it is routed out the "bypass to-heater outlet" and goes to the "heater core inlet." Then it goes through the heater core and out the "heater core outlet" to the "water pump inlet tube" on the water pump.

So, intake manifold to bypass valve inlet, bypass valve "out" over to the heater core, then out of the heater core to the water pump.

Of note: if you dont' want to heat the heater in summer, or don't have one, you can run a hose from the manifold outlet to the water pump inlet directly. But be sure to do the same with your heater inlet and outlet (and the heater full of coolant to prevent corrosion).

Make sense? I need a beer!

Happy Friday!

Julie!

 

Ahh...I missed that (admittedly, I did not read the whole thread-just jumped into the middle when asked). Sorry about that.

Brian

 

No Sweat!

Ya know, sometimes I sit and write this stuff and I check it and edit it until it's right, then a little later I'll go back and read it (like the response I wrote to you) and it's a mangled mess of cut and paste and typo's, etc etc. And I just sit here and ask myself if I'm gonna stop smoking cheap dope! (kidding!)

In all fairness I think sometimes the corrections I edit in don't get posted. But, I like to be sure I'm helping and not confusing!

Can't blame spectators if they don't read it all, I tend to write long answers so the info goes to the person doing the work.

J!