I know this has been hashed out as I've read all of the past posts reguarding the high output heater core that was available in 1977.5-1979 Ford trucks.

Now, this is what I have in my possession: Heater core with part number on it and the box as D3TZ18476A. There is a past post that states that this core is the ECONOMY type, but alas it isn't. The unit I have measures 8x6x2; the high output core.

I went to the FoMoCo part number decoder page. This number decodes as this: D - the 1970's; 3 - last digit of year of introduction or revision; T - truck and Z - Ford service parts.

Now, the question I have is this: If in fact the number 3 states that this part was INTRODUCED or was revised in 1973, that would mean that this existed PRIOR to the high output heater option of the late 70's.

Unfortunately, the only date on the box is October 18th. No year; except for a small '75 in the lower left corner.

Did I read/decode this part number correctly?

By the way, I have a 1973 F-250 4x4 with factory AC.

 

Your assumption is correct the Hi-output heater was available prior to 78/79, it came on trucks equipped with the "Northlander" package and was standard on most if not all crew cabs and supercabs (more cubic feet to heat).

 

Thanks Montana - this is interesting. My truck was originally sold in Colorado Springs, CO and I wonder if it has this "northlander" package. It's only a standard cab though.

I do have the build sheet that I found under the seat. Do you know how to decipher that?

 

I know the Northlander package came with dual batteries, engine block heater and hi-output heater, what other features it might have had i'm not sure.

 

My 76 has the high out put heater and I bought it in texas, there is no air and it never had dual batteries, so it must have come in some that didn,t have the whole northland package.

 

Mine had a 360, block heater and only one battery.

What I'm having is this darn low temperature air from the heater problem. Fan blows real nice and I've already checked ductwork, etc. I flushed it out yesterday. Hoses hot on both in/out - in is hotter than out is too; but both are hot.

Running 195* T-stat, hood blanket, grille cover and electric fans set to off. I believe the truck is coming up to temp as the guage is about 1/3 to half in normal.

I just don't want to tear it apart to find that it may have the larger core in it already with me just expecting too much out of it. The truck is 36 years old ya know!

I'm afraid that I may be victim of someone else putting in the smaller core when it had the larger one in it, leaving that 2" gap.

 

With all those measures taken you should have ample heat, my heater is only the economy core (6x6x2) and it virtually roasts me out of the cab even on low.

 

Something is not right it should roast you out even at alaska temps, but air takes the path of least resistance so if it can get around it it will. Where you at in ak.

 

D3TZ-18476-A Core Assy., Heater Fits 73-up F100-350 w/ integral A/C or Hi-low vent system.
C6OZ-18476-B Core Assy., Heater fits 73-up w/ High output (8" core)

 

I'm in Eagle River; basically south-central just north of Anchorage.

Ambient temperature today is 28*F. Took truck out twice today and got her all warmed up. First time, the heat was like before - just kinda luke warm. Second time, it was noticably warmer, basically like I think it should be. I don't know why it got warmer on the second go around.

So Mike, if I'm reading this correctly, my truck should have the "high output" core in it already, since the one I have in my grubby hands is the D3TZ part # and it measures 8x6x2.

I have an idea: I suppose if I could get all the coolant out of the core, measured it and put it back in and see if it's the same amount that the core I have on my bench takes. That way, I'd know what size core's in my truck before I go ripp'n stuff out.

Thanks for the help so far guys!

 

Here is a thought it has been a few years since I have changed a core in one of these, and I can't remember if they set in the foam padding that went around some of the cores or not. If so we used to have trouble with the foam disintegrating and it had to be replaced for the heater to be effeciant.
Yea I know exactly where eagle river is I hang out at fairbanks but get through there some.

 

You may be onto something starmilt, as the core that I'm in possession of does have the foam around the sides and bottom. Only the top doesn't have it. Maybe it disenegrated and there is a gap letting cold air pass by the core.

I just wish I could see in the box w/out removing it!

 

There is a pre-formed foam padding that goes around the core to seal it in the heater box.

But like Montana said, I have the standard heater and it will roast you. I love the looks on people's faces as I pass them wearing a t-shirt and they are in their Toyota Camry's all bundled up.

The heater works so good, That I can turn the fan OFF and just have the ram air effect thru the cowling heat the cab plenty at 50 mph.

Josh

 

Check with some local auto shops, diesel shops, most have a small flexible tube with camera on it to see inside engines, You might be able to borrow or rent. Home depot also has one for sale not sure how much, used to check inside walls and such.

 

That's a good idea Moose - I didn't even think of that and I'm in the HVAC business!

A "snake-light" would work good - maybe all I'd need is a 3/8" hole or so to get the camera/lens end it to take a look see.

That's why I love these forums - so many good ideas!