so as a spur of the moment thing this morning we decided to finally replaced my heater core. Installation went fine, only took me and my dad 4.5 hours. Which from what read is about twice as fast as most people on here.

We put everything back together and turned on the heat. Turned to defrost, then to the vents. It didn't change to the vents, still blew through the vents.

there is 4 vacuum lines that are visible under the dash, 2 on each side of the truck and they are connected. So I'm not really sure what's wrong, I'm assuming it's a vacuum leak under the dash but we are just leaving it for today. Thought I'd ask you guys what you think could be wrong.

It's a 1999 Dakota with a 5.2.

 

I'm not following how you tried the heat. Is it coming out only on defrost?

From your description of 4 vacuum lines you don't have a/c but there should be 5 vacuum lines.

Yellow/Blue work the floor/defrost actuator
Brown/Red work the panel/defrost actuator

Black needs to go to the vacuum reservoir. It supplies the vacuum for the doors. No vacuum, it defaults to defrost. Find the black and you should have it.

Good luck. You were quick.

 

Sorry for the vague description, I was about asleep lol. When I turn the vents on, whether it be floor or panel vents it only blows from the defrost vents. Regardless of the panel I select. I'll look tomorrow and see what color lines I can see, maybe I will be able to find the other line. If that's what it is.

 

I just remembered that I did see a black vacuum line. It ran to a tee above the brake booster. I did disconnet that line when we removed the heater core. And I do remember reconnecting that vacuum line before we had everything put back together. So unless there is another black vacuum line besides that one I don't think that particular line is the problem.

On another note I checked my cruise control when right after I left my dad's and it fluctuated 10mph and couldn't hold it's speed. But 10 minutes later when I got on the highway, it held the speed steady at 65 the whole 10 miles home.

I'm still sure it's a vacuum leak somewhere, but cannot think of anything unless we somehow punctured one of the lines somewhere.

 

Well I woke up this morning and it was still acting the same. So I just planned on messing with it after work.

Got to the bosses house where my truck was and popped the Hood. Disconnected the vacuum line, reconnected it and still did the same thing. Took the vacuum line loose two more times while running, same thing.

Took it off one more time, rubbed my finger over the tee and the line going to the firewall, and it blew air out of the vents.

I'm guessing some dirt or something got in the vacuum line somehow and either it sucked it all through or I knocked it off.

So now I got heat and vents working. Now just need to buy r134a and recharge the AC system and I'll be good to go. Thanks for your help

 

Glad to here you got it fixed, ive only changed out one heater core in a 89 mustang gt and i hope to never have to do it again