Heater blow's only cold air

[Jrgunn5150]

So I'm going to go pick up my truck from Cleveland next weekend and start driving it again since it didn't sell for me and I just remembered something. My heater only blow's cold air, and I have no idea why. Now I don't have the truck here to look at, and I can't remember if I put a thermostat in it or not last time I had the intake off. I probably did though, but if I did it's probably a fail-safe, so I can't rule that out, but I want some other ideas so I don't have to drive 400 miles in the cold if it's not that!

So my ideas are these, if it's not the thermostat:

I put the heater hoses on backwards, can you do that? Does it matter? I thought it didnt, but I've been wrong before.

The other thing I have come up with is a guy at work said my vents and ducts are controlled by vacuum, and I may have lost a line, so the duct defaulted to open to the outside. Is this true? If so how do I fix it?

thanks alot guy's.

 

[jakes4321]

I just did 2 s10 blazers that the thermostats stuck open, just blew cold air. Do you have a temp gauge? where is it sitting? I would check that first.

 

[AKbigsub]

Low on coolant???

 

[4X4HIGH]

Either your heater control doors aren't working properly or the heater core is plugged. This is assuming that you do have a thermostat installed that isn't stuck open.

 

[BobK]

Feel the hoses going to and from the heatercore.
If one is hot and the other is cold the heater core is plugged.
If both are hot it's possibly a blend door problem.Check vacume lines
If niether are hot check coolant level.

Even if there isn't a t-stat. the heater core lines should at least get warm.

Just a few things to check anyway.

 

[diesel4me]

Truck sat for awhile??...

If your truck wasn't being driven daily, I'd be willing to bet Mickey Mouse built a nest in your heater box!...I see many nests in vehicles that DO get driven daily around here,including MY truck! ...look for nut shells on the intake manifold,if you see any,its probably a rats nest blocking the door from shutting in the heater box,if the heater hoses feel hot,and no cables or hoses are disconnected on the heater box..

I thought my heater core was plugged in my 74 K20,I couldn't get much hot air to blow out of the ducts..checking all the cables proved nothing wrong there,so I replaced the T-stat...still no heat!..flushed the heater core out with a garden hose,it flowed perfect,no cloggage!... `

Then I decided to yank the blower motor out--when I did I found a TON of that jute padding under the carpet JAMMED in there,the blower wheel was the only space that was not blocked!..stunk like ratcrap and piss too,droppings were everywhere!..two minutes with the shop vac,and Ta-DA!..nice hot HEAT again!..a little bleach and Lysol helped sterilize the heater box..I found one mouse in the shop vac when I went to empty it!..

I just helped a freind re-wire his mom's 1995 Buick Skylark unde the hood near the firewall-mice chewed the wiring harness to hell,and she took it to 3 garages and spent 500 bucks ,trying to solve driveability problems!..yeah,the car runs MUCH better with ALL the wires connected!..

I found it hard to belive THREE shops couldn't find anything wrong,yet replaced a bunch of sensors and other parts,and charged her that much!--and it was still screwed up!..I saw the butchered wires in about two minutes!..when I went to touch one wire I suspected of being bare,the car stalled!.. ..she's going to try to get a refund..

 

[Jrgunn5150]

Cool, thanks alot guy's, I gotta print this page out now.