heater not working..

[LANCE65]

I have replaced the heater core,heater hoses,heater control valve,192* thermostat,and antifreeze in my '71 F250. Has the under dash ac unit(w/glove box). My question is, does anyone have an exploded view of how the underdash unit is assembled? Both of my heater hoses are HOT and the air coming out is only luke warm!? Thanks
-Lance

[kaptnkaos]

Hey Lance...

Question for ya...
My '68 w/390 has a second on and off valve...
One is controlled by the temperature lever inside...
The other is on the block itself where the heater hose goes into the intake.
If that is turned off, it won't let water cycle thru the heater core.

KaptnKA S

[fordman]

i think in interior kieth posted a pic of how theheater hoses and vavle were suppose to go on to the factory a/c box. i think the valve comes off of the intake side and had to be in the right direction to open properly with the inside lever.

[LANCE65]

I have all of the routing right, I just dont know about the underdash unit. I had it COMPLETELY apart. I just want to know if I put it back together right. Thanks
-Lance

[fordman]

oh ok maybe the cables got switched around when you put it back. the factory a/c has four cables as you know.

[FORDification]

A couple years ago when I tore mine apart, I took some very detailed notes on what goes where, and also took some pictures to help me in the future. It took me a few minutes, but I just found the notes. I'm going to spend the rest of this evening putting together a photo tutorial to illustrate the proper hook-up for the four cables.

[warponyxlt]

just puttin in my but did you try flushing out your core. I did once with clr a bunch of gunk and silicone came out problem is they are still not that warm but better than before

[FORDification]

OK, the new tutorial is completed. Click the following link, which should answer your questions on what cables get connected where on the factory A/C setup:

Factory A/C Control Cable Hookups

For future reference, this page is linked to from the Technical Articles Index and the Site Index.

[LANCE65]

Thanks Keith!

[samwhiskey01]

I am having this same issue .. checked air temp at underdash unit it barely above 100 degrees. Did anyone find a solution ??

Also, heater control valve, heater core, hoses, radiator, thermostat, all replaced.

Water traveling TO and FROM the factory installed A/C unit is hot but still the air being blown from the cab vents is luke warm at best. Water temp at the radiator is around 180 degrees. ?? Any other thoughts before do another dismantle of this lovely A/C unit ??

[FORDification]

It's very possibly a plugged heater core. You might be getting some coolant to go through, but not enough to really heat the core up. I'd try flushing the core to see if you get anything to come out.

You might also consider jumping up a notch on your thermostat. A 192* thermostat is better anyway, especially in cooler ambient temperatures.

Another possibility is simply a control cable out of adjustment....the one to the control valve. If the cable isn't allowing the valve to open completely, it's not letting enough coolant through to be fully effective.

[LANCE65]

somehow I got the doors blocked,so I disassembled it again and fixed it. Thanks again.
-Lance

[samwhiskey01]

I just replaced my heater core and having replaced the heater control valve made sure to adjust the cables accordingly ... any other thoughts here ?? The hoses going to and from the A/C unit are measurably hotter than the air coming from the unit itself. As I see it, at this time of the year, I should be BARELY able to stand being in the cab with the heater running full blast !! ??

Corn-fused !!

[Joshpow]

No help here, but the heat in my 72 comes compliments of Carhartt!!! Mine has never been great on any of my bumps. I plan to try a new heater core to see if that helps. All of them have lukewarm air. I just began to think this is absolutely normal!

[qmcdugan]

When I took mine apart I found a delicate little part # 18591 depicted in a picture you should be able to find at this site. In the upper right quadrant of the HEATER PARTS - FRESHAIR you'll see the heater hoses that connect to the core. Below that you'll see the wires that connect to the heating element that can be found inside the heater core housing assembly.

Now I'll confess that the reason for this element is to provide some warm air till the engine takes over. Unrelated to this delicate part just discussed, the heater system in my 70 F-100 now works great, the 68 I don't know about since its under reconstruction. But what I did find when working out the demons in the 70 was a complete mess regarding the Inline HOT WATER Valve that is controlled from inside the cab. Cost $30 plus S/H from LMC. Recommendation, if you'll spend $99.00 on parts from LMC you can optimize your shipping costs. Just don't scrimp on getting heater ducting. The plastic stuff works if you warm it up some as it is very stiff and difficult to work with.