[JeffO]

I bought my 2002 S10 about a month ago. I drove it home and the heater barely put anything out, and the next time I drove it, nothing. Previous owner said heater and 4wd both worked. The truck sat for about 6 months, and neither 4wd or heat worked when my mechanic looked at it.

Symptoms were, warmish air for a second, then cold, and all the vent settings acted the same (feet vents, face vents, defrost). They just blew cold air.

Coolant was pretty low, but topping it off made no change.

I got a pre-purchase inspection done, and got some more major systems tidied up (transfer case, control arms, 4wd, vacuum lines). The vacuum lines were rotted, and a shop replaced them (4wd works now and vacuum reservoir holds vacuum pressure).

With the vacuum lines in, the max AC now sucks in cabin air for the intake; it didn't do that before. There's no improvement or change in the heat.

The coolant lines through the firewall seem to be circulating. After a drive to work, one is significantly hotter than the other.

It seems like cold air is getting sucked in. I wonder if a vent baffle is broken or not actuating for some reason.

Thanks in advance for ideas or suggestions.

 

[Rhotpursuit]

Best bet is the heater core is plugged up. You might be able to clear it by back flushing it....both directions.

 

[oldeerslayer]

X2
If one hose is hotter than the other the core is likely clogged. Take both hoses off and run a garden hose into each heater inlet. When removing the heater hose I prefer to cut them off with a utility knife with a sharp blade just past the clamp. There is enough extra length to reattach them. After removing the clamps cut the remaining 3/4" lengthwise. This prevents twisting on the delicate inlet pipes. If you should damage them it's a big job to replace the heater core. Put on a length of the appropriate size hose on the one the coolant/water will come out of and stick that in a 5 gallon plastic bucket to see how much crap was in there. Then do it the opposite direction. Don't clamp the garden hose onto the inlets. Too much pressure. Just hold it up to it. Bet you get a bucket full of crud.
If your doing this outside in single digit weather do it quickly so the core doesn't freeze up on you. Once you reconnect the hoses antifreeze will quickly fill the core. Or wait for a day above 32°F.
BTW if your mechanic found one hose hotter than the other and didn't suspect a clogged core, find a new mechanic. A lot of vehicles do this and any experienced tech would know that.

 

[hogster]

"BTW if your mechanic found one hose hotter than the other and didn't suspect a clogged core, find a new mechanic. A lot of vehicles do this and any experienced tech would know that. "

couldnt agree more!!

 

[Walleye Hunter]

Max AC does recirculate cabin air, that's how they get the 'max'. Rather than bring in hot outside air, the already cooler inside air is recirculated. I like to push that recirculate button when I'm stuck behind a stinky vehicle too.