I am changing my heater core this weekend and the parts store lists 2 different type cores, how do I know if I have the high output heater or the standard ? I do have A/C.

1979 F-150 Ranger 400 with A/C

 

I was under the impression the hi-output core wasn't available in the a/c model. I have both, the a/c truck has the non hi-output version.

 

And I thought the A/C version was automatically the high-output core, no option for the standard output.

If the parts store has both in stock, pull your core first and match the size.

 

I agree. I base my opinion (only opinion because I didn't measure the a/c core while I had it out) on that my a/c & heater controls don't say hi-output on them and they do on the non a/c truck.
When in doubt though take in your part to confirm.

 

My F100 is high output(no A/C) but like macguyver said pull it first and match it up.

 

I was trying to avoid that because the parts place is a good ways away. Well gotta do what ya gotta do. Will l let ya know for future reference.

Thanks

 

this is a job for a Canadian! Here's my 1.58 cents:

All the suggestions are good ones and I have tried them all over the years. often a combination of circumstances. It must be remembered that these trucks get a lot of air cooling through the front and the cab etc which is why all of a sudden when the mercury drops cooling deficiences show up.

Cardboard is essential but I shy away from using it until I am sure the low temperatures are here to stay.

The cab leaks a lot of air sometimes and installing new window felts etc really cleared up some drafts. I also have the custom fit heavy rubber matting on the floor with insulation in the foot wells.

Make sure other air infiltration is kept to a minimum whether through vents, missing firewall grommets etc.

Always run the hot thermostat recommended by the factory

make sure cables are connected properly so that when you shove on the warm air lever it actually opens the valve all the way--those cables can fall off and fiddle about

make sure then that the lever the cable attaches to at the plenum will fully. I had to lube mine up

Wash out the heater core or replace. Do this by flushing it both ways with a garden hose or pressure washer.

Install a clutch fan

In really cold weather I find it helpful to let the engine get up some steam before driving, sort of get a jump on the wind chill.

 

My 77 is the same way. The heater puts out great heat, but the drafts are bigger than the heater. I nees new window felts and vent window seals. If I start it and go, it won't heat up in there until spring. If I let the cab heat up first, then it is ususally fine unless taking a long trip.
Go ahead and flush out the heater core and then shrink wrap the whole truck. That will keep those pesky drafts away!!

Jimmy