99 trailblazer wiring question

4xrick · Dec 8, 2013

I just got a call from a buddy who has a 99 trailblazer and replaced the heater core, to do this you have to remove dast (stupidst thing ever)

but when he was all done there is a plug coming off the main box that has 4 wires on it brown blue orance and black, and says they are fairly thick wires. he said the rig runs and drives but it has no heater controls and no speedo a few other misc things not working, he canno9t find where it goes and does not remember unpluging it, now in this weather his wife and kid have no heat, anyone who knows these rigs know?

crash2 · Dec 9, 2013

You mean blazer? I love doing those things...

crash2 · Dec 9, 2013

The one connector should plug into the HVAC head. So pull the center cluster bezel and pull the head. I assume the wires head to the pass side of the dash(they lead into a big connector at the pass side of the dash).

As for the cluster there are a few connectors that are on the drivers side that probably got forgotten.

zuk88 · Dec 9, 2013

I did a few of those, what a pain! I remember having one connector on the pass. side where it drove me crazy because I couldn't find where it plugged into but found out from looking at another one on the lot it was an unused connector.

4xrick · Dec 10, 2013

I got it all torn apart tonight and found the plug, got it all put back to gether and a couple other things taken care of om the rig. then they get almost home and call me saying the thing is blwing air but it is ice cold. he says the temp guage never moved from cold and both heater hoses are hot.
is it possible that the heater core is just not flowing or how else would it be ice cold air coming through the vents?

my only thoughts are vent controls not working or the actuator maybe?

zuk88 · Dec 10, 2013

With the gauge not moving it could have a thermostat that is stuck open not letting the coolant to heat up enough.

4xrick · Dec 11, 2013

I thought about that to but the fact that both hoses were hot as Hell acording to him would make me think they should get at least.some heat, not ice.cold air.

zuk88 · Dec 11, 2013

That would be the cheapest thing to try. You can pinch off the upper rad. hose and see if the gauge goes up and the heater gets hotter too.

4xrick · Dec 11, 2013

i havnt got the thing back here yet, I will be messing with it this weekend. durning the week i work 10 to 12 hr days right now so after that and a hr commute each way i am way to beat to look at it.

zuk88 · Dec 12, 2013

I know your pain brutha! Its hard to get motivated to even work on my own stuff some times.

JOOP · Dec 12, 2013

Possible the thermostat is stuck open.

crash2 · Dec 12, 2013

Even if it was stuck open you would get some luke warm air.

zukkev · Dec 12, 2013

It's a blend door issue...if both htr hoses are hot, the coolant is passing thru the core just fine...Keep in mind on these things the coolant is flowing thru the core all the time---the temp control is done via the blend door(s) in the heater box assembly. I'd be going after an issue with the controls...

zukkev · Dec 12, 2013

4xrick said:
I thought about that to but the fact that both hoses were hot as Hell acording to him would make me think they should get at least.some heat, not ice.cold air.

Not if the blend door is in the cold position...

4xrick · Dec 13, 2013

zukkev said:
It's a blend door issue...if both htr hoses are hot, the coolant is passing thru the core just fine...Keep in mind on these things the coolant is flowing thru the core all the time---the temp control is done via the blend door(s) in the heater box assembly. I'd be going after an issue with the controls...

this is what i was thinking, when i said some warm air i was meaning if the door was working and the thermostat was stuck open.

i am hoping it just the control did not get plugged in all the way but i have a feeling it may be the actuator for the door, seems to be a common issue.

crash2 · Dec 13, 2013

I am thinking an actuator did not get plugged back in since the heater case has to come out.

zukkev · Dec 13, 2013

4xrick said:
this is what i was thinking, when i said some warm air i was meaning if the door was working and the thermostat was stuck open.

i am hoping it just the control did not get plugged in all the way but i have a feeling it may be the actuator for the door, seems to be a common issue.

If it worked before, and not now...I'd bet crash is right...no pluggypluggyinnee...