Heater/Defrost Issues

[mlb200180]

Ive been trying to get my heat workin. My windsheid isnt defrosting all the way and the other windows keep fogging. I replaced my blower motor in the fall because leaves were getting in the heater box and the motor failed. I had a leak in the core. Cleaned the leaves out and replaced it. I dont think the temperature comming out of the vents is high enough. Also I dont think there is enough air comming out of the vents compared to a newer vehicle. I think my hoses are right. Small hose from the bottom going to the water pump and big hose from the top going to the intake. QUESTION! Does the air going through the core come from the outside? Thats what it looks like. Was wondering if that has anything to do with it. My truck is a heat only cab, no ac.

[kevmic28]

My heat only cab sucked, I installed a complete ac system and it blows so much harder. But I still have issues with windows and defrosting. If I crack the window just a little to let the fresh air in the windows defrost better.

[scrapmetalart]

Is your motor getting hot enough? have the right thermostat in it? is the radiator full?

I have a 6 cly with a heat only cab & it gets plenty hot. takes a min but gets hot. not like a new truck but plenty enough...

[mlb200180]

Ill have to try a hotter tstat. I have a mechanical non/clutch fan. Its been cold and temp guage never passes a quarter of the way.

[JimKshortstep4x4]

The heater hoses are hooked up backwards as you described them. Large hose from top goes to the water pump and small hose from bottom goes to manifold. I am not sure if it will make a lot of difference.

Check the blower switch as it might not be functioning for the three speeds. The temp gauge may not be reading correctly. Outside air does go through the heater.

If you get everything working, the heater and defroster will work for you.

Here is a schematic of the heater hose routing.

Jim

[Lee H]

Welcome to 40 year old technology.

[LockDoc]

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My bet is that you have a mouse nest and other junk blocking your heater core. You have to take the outside heater box off to clean it out.

There is nothing wrong with this 40 year old technology when regular maintenance is performed on it.
LockDoc

[PanelDeland]

Lockdoc is right.My 68 has better airflow and hotter air than my 2000 Dakota.I replaced the core,the fan and cleaned everything up.I also put in new hoses and air duct tubes.I did plumb it backwards to keep the hoses neater.Not only that but I replaced the radiator with a 4 row,really keeps the 6 cool.The left tank is so hot you can hardly touch it and the right is almost cool enough to drink.

BTW I also have waaaaaaaaayyyyyyyyyyy more cab to heat than most.

[matthew20061]

Are you getting full power to the blower motor when you select full speed, I know on some of my trucks the switch even though it goes all the way only selects the medium speed, instead of full speed on the fan motor.

[BLACK AND BLUE 67-72]

The heater in my 72 will run you out, you either have to turn it off or open a window. I went completely through my heater box, new hoses, new heater core, cleaned and painted inside and out and put a new 180 thermostat in the truck. I have no problems at all about it defrosting!!! lol

[scrapmetalart]

Originally Posted by mlb200180

Ill have to try a hotter tstat. I have a mechanical non/clutch fan. Its been cold and temp guage never passes a quarter of the way.

the ol pizza box in front of the radiator helps when it gets real cold

[mlb200180]

ill have to try switching the hoses around and get a hotter tstat. the blower is getting about 13 volts on hi spd. i dont have an air flow prob because i previously changed the core and cleaned everything. its been cold in MO. i need to start cookin. thanks for the help

[cdowns]

the air diverter box is important part in defrosting// it is a very common failure fot the flapper valve to brake

you should have a 190degree thermostat

[camrycurt]

Originally Posted by scrapmetalart

the ol pizza box in front of the radiator helps when it gets real cold

I'm completely new to older vehicles and have seen where guys have done this but I don't understand what it does.

What problem does putting cardboard in front of the radiator help with? What are the symptoms that would indicate this would need to be done?

When you do it, how much of the radiator should be blocked off, and for how long?

Thanks for the help!

[dmack91]

Cardboard or similar in front of the radiator will limit the airflow through the core at speed, retaining more heat. It is used by many trucks in areas where the temp gets below freezing to help keep the internals warmer.