Canadian Hummer Club Forums

So my rig has no heat. Fan blows but no heat on front or rear vents. Control valve moves easily by hand. I get no vaccum at the coolant control valve. What is the next step? Do i assume it is the hvac control panel on the dash and just replace it? Anyone have a spare unit to swap and make sure before ordering? Do this part cross over to napa or something so i can get locally?


Thansk for any help given.

Check the Vac pump first.. They fail
 
Not sure if you are turboed and the wastegate control exists. (mine is mechanical) Depending on year.. heater or wastegate control.. good indicators your vac pump is boned.
 
If the valve moves by hand and yet no heat...= no hot coolant to your exchanger. Should be pretty easy to determine by the temps in and out of the valve body. 
 
Did you try Flash Offroad or The Hummer Network yet? Usually good troubleshooting info there. (better than mine anyway)  :)
 
Let us know,
Derek

by the sounds of it, there can be 2 issues

That's if your Tstats ok, and no air in your system...


1) even without vacuum, (if I recall correctly) the water valve is set to flow (engine coolant ) through the heatercore, in that case you need to try to flush it, or you might need a core ,

To test this issue, as stated, hold the lines going in and out and see if one feels noticeable different in temp..


2) if you head unit isnt opening and closing the control valve, (imo most common) there can be a vacuum issue,it's very common to have a week/bad vaccum pump.

Orrrrr, (if your lucky) you can have a broken/ cracked rubber hose,


3) I'm sure a head unit can go, but not sure how probable that would be



If you flush it this is the factory direction ,

Thanks guys. Yes I am turbo'd. I will check for vacuum tonight. I decided to do too much at once so now I am into draining trans and t-case so I could not run it last night. 
The t-states and coolant are getting done next as the truck runs around the 170 ish down the highway and about 200 for large up hills then right back down to 160 or 170ish. I am a true believer engines should run at t-stat settings. 
Little over excited to do all the fluids and get it to where I know what has been done to it!!
 
Do you guys buy those inline heat flush kits and leave them in?

Wow your truck runs much cooler than mine. Mine has stock T-stats, new cooling stack and Evans waterless coolant but runs 195 - 220 depending on the day and load. The system was all flushed when this was all installed recently but nothing was left behind (flush kit).
Hopefully you get lucky and it is a simple cracked vac line or failed valve as Monk said. My vac pump failed last year....needed to replace it even though as far as I can tell it only runs the HVAC controls now....haha.. 
Seems the only damn thing I haven't replaced or overhauled in the last 2 years is the heater controls. Think I just jinxed that. 
 
Fortunately there is tons of good help on here for your issue. Monk is overhauling something weekly it seems. Roy knows all the little H1 tricks and details too. 
 
Derek

I'm planning to do the flush .....lol sometime

But instead of installing a "T" (didn't want to flush full system) just the cores

I will be removing the 2 hoses in the back of the water valve ,


Then (gonna buy at princess auto) water hose 5/8 barb line in the pressure washer section

So I can basically connect the water hose direct,. And do the top line first and lol go slow, till there is flow...dram into a large bucket

But again if she plugged solid, it needs to get a new core,.,,,

If not plugged then wait till semi clear water comes out and then switch and flush from bottom up and vice Vera to mix things up...



160 seems cool, down the Hwy ( like you said, should be at 195 ish) .... Never know Tstat might be the trick!!

Like you said "NO" heat,

I'm assuming no front OR rear heat?

Hopefully the fronts not plugged solid....and nothing flows threw

The cores run in series, and both to be plugged at once would be a coincidence......the more you describe might just be a nice easy stat job...

While your coolants out its good to give a little flush,,

ddgermann , lol ya seems like that, but I procrastinated way to much..,

I'm trying hard to try to keep on top of things more this year, hehe

Hence my many Roy's shop visits,...,

I'm hoping come summer it'll just be cruise and tire shine time, hehehe

Thanks guys. I will do all of what was said and let you know what I find.
Both front and rear blow the same no warm heat! LOL
 
Should have all this complete this weekend. 

Update
 
OCD kicked in this weekend. LOl
 
Never got to the flushing part but did figure out I had plenty of vacuum. But with the control unit to heat I did not have vacuum at he water control valve. So After a few phone calls and finding out the new unit would be $230. I decided to go to Kenny u-pull and try a used one first. I found a newer style with the larger knows and chrome rings and bam! 16 dollars later it works. Control valve now has vacuum. However I still have luke warm heat if that. So that being said is why OCD kicked in. I dd not get to the flushing. I got side tracked and completely re did the birds nest of stereo system wiring, all the duct work under that dash not correct or warn, all seats had at least 2 bolt loose or missing and redid the entire fronts drive shaft, greased all 10,000 grease zerks!! 
 
Again will let you all know how the coolant flush goes. I will also change the control valve while the system is empty.

When testing the heat, do it on a run. The diesel cools off and the water pump does not circulate at an idle that well.