I couldn't get the heat to come on in front or back. It would only blow cold. Then I got a puff of smoke out of my front middle vent and the heat came on.

I still can't get heat in the back though.

Any ideas?

The a/c works just fine.

 

Welcome to the forum...
What year and model are we talking about?
Are the heater hoses to the rear unit getting hot, you can find the lines under the passenger side rear quarter panel... if the lines are hot then hot coolant is getting there but you may have a blocked or clogged heater core....

What does the anit-freeze look like? if the newer style dexicool is mixed with the green stuff it will make a cottage cheese mess in the system and clog the lines...

 

heater core.

 

Sorry, it's an 05 Z71 2 wheel drive Tahoe.

My husband seems to think it's not the heater core. He said if the heater core had a problem then my tahoe would be leaking antifreeze.

Is that right?

 

It can simple be clogged up and not leak...
feel the return hoses from the heater core, the hoses should be *similar* in temp, if there is a big difference in temp of the input and return hoses you likely have blockage....
You can try removing the hoses and reverse flushing the core, but its no guaranty that it will resolve the problem...
being an 05, has the cooling system ever been serviced?

 

in2pro is correct, not that he/she needs to hear that from me. A heater core can leak two ways and plug one way. A plugged core will not leak but will stop heat. A leaking core may not leak, meaning the leaking fluid will instantly evaporate so with that is usually a faint or strong coolant smell but no visible leakage and usually heat is not affected. The obvious is seeing the coolant on the passenger floor and usually the heat stops working. Either way all scenarios require a new heater core and unfortunately it's a cheap part that does a simple job but takes time to get to. I think most heater core replacements on suburbans at shops run 6-8 hours labor. I believe a/c would need to be recharged as well as old fluid disposed and new installed. Not a at home job for most.

 

Okay so, my husband knows how to change the heater core and charge the a/c. Problem is he's now decided that since summer is arriving it is not a priority issue. If the core is plugged up will it eventually start leaking if not fixed now?

Also, I didn't have heat in the front at first and then finally it came on. Is that still indicative of the heater core?

Thanks Everyone!

 

And by the way, my husband does mechanic work and is an electrician. As you can probably see from my posts, he also thinks he's a know it all and is always right. Makes for trouble when it comes to my vehicle.

I'm quite particular about what I drive being in top shape.

 

Diagnosis over the internet can be a challenge....
IF the heater hoses both inlet and outlet are both similar in temp it might not be blocked, it could be a blend door issue...but if the AC is working in all likelihood the blend door is also working...
I wouldn't wait till it gets cold to do the fixing... just sayin'

 

I did what your hubby is saying and I'm still good. I have a tiny leak where it evaporates immediately leaving no visible leaks, even when I scoped the core and the area around it and below it with a tool I borrowed from a mechanic friend I could see no leakage even at the supposed leak area, but being we checked everything from cabin filter to blend door to entire engine bay and hoses and found nothing we are assuming with high probability it is "fractional" leak. Being I know what coolant smells like and it only smells during use of heater, even if fan is off but heater temp dial is turned to mid range or up it has the faint smell 50% of the time. My heater blew cold air a few times with heat on but has not since so I don't know what to think of that but bottom line is if you are blowing cold air all the time or sometimes it's the heater core period. Whether it will begin leaking from a block is anyone's guess, most likely it won't anytime soon but one never knows. So if the fix can be and needs to be held off for financial or time restraints wait but don't wait until it's freezing. If he is doing the work then either you tell him to do it as a wife, lol, or wait it out. Most likely it won't leak before a fix within 6 months but if it does it will ruin your carpet up front and of course be more work and stress. Because I am re-carpeting my burb this summer during stereo install I'm waiting it out and have since late July and no issues other than a little smell.