Reason i noted that it affects both sides of the vehicle is because i'm very aware of the common blend door actuator that goes bad on the driver's side. I've replaced mine before.

Issue i'm having is i get more heat on the vent setting than i do the floor setting. Basically, it's warm/hot at the vents and also the defrost, but cool on the floor. And if i do the mixed setting, it's still warm above, and cool on the floor.

Even on vent setting though, the heat will fluctuate. It will be hot for awhile than cool off a bit and get warmer again. But it always remains warmer than the floor.

I know it can't be the tstat, i replaced that at the beginning of this year along with flushing out the heater core.

I guess the only thing i can possibly think of is the actual temp. blend door itself...?

anyone else have a similar issue, or know exactly about this issue?

 

Do to the fluctuating I wonder if you have air in the system. I'm not sure why it would feel different from other settings tho..

 

Anyone else have any ideas?

 

had a similar issue w/my 04 SS no heat on left side,im not a mechanic so i broke down and took it to a dealership (ok aussek 2000) they fixed the problem for $254.50 so now i have heat on both sides and if it f--ks up again its on them. nuff said! its all electronic man.

 

Right, but this is equally both sides. I am a technician as well. Of course I work at a ford dealership though so no one there really has any input. It's a strange issue. Heats up normally on the vent setting, but remains cool on floor setting.

Has to be a blend door issue I'm thinking.

 

The vent setting....means that your prolly getting heat from the compressor/AC when you turn your controls to heat......

Do you get heat also from the defrost mode???

Heres what I think is going on:
You said you replaced the Tstat a year ago...and flushed the heater core....Does this mean you also completely flushed the radiator as well?
(Maybe gunk replugged the heatercore?) If you didnt flush the radiator as well...

Heres another possible issue:....
Lets say for instance, you flushed the system out with the "new" Tstat in place. Me thinks if this happened...Your Tsat is plugged?.... Thuis it opens a tiny bit enuff for ...some...heat and then shuts when it gets heated to operateing temperature...or the opposite and stcks wide open!
What operateing temps is it running at? R U haveing an over heating issue as well?...

Or the last possible Issue your haveing....Is way too much antifreeze in your system...which is "worse" than not haveing enuff anti-freeze...Haveing to much anti-freeze also causes your heater core to fail....Meaning it will no longer ,build,hold heat....Kinda like a battery with a dead charge on it....

So, your heatercore could be junk...and need to be replaced...!!!

This should keep ya busy for a while....I think 1 of these soulutions should resolve your problem...

 

I'm wondering this myself. There will always be a slight difference/fluctuation in temp as the thermostat opens/closes, but if it is significant air trapped in the system could be the cause.

Also, there will always be a slight difference in temp between the dash vents and the floor. Since heat rises and the dash vents blow air towards your face the air from them is always going to feel warmer than that coming from the floor vents.

I would try bleeding the cooling system and see if the situation improves, but you're never going to see equal temps comparing the dash vents to the floor vents.

 

I guess the fluctuating isn't a issue at the moment.

But I do have heat on defrost as well. No over heating problems. Heat works wonderful up top. Hardly at all on floor. It's very noticeable. It's a BIG temp difference.

I'm thinking it has something more to do with an HVAC component other than the heater core. It just doesn't make sense to me that heat wouldn't get down to the floor but works everywhere else. It worked just fine last year. Like I said, the temp difference is very significant.

Also, I did bleed the cooling system after the tstat was installed and after the heater core flush

 

If you're getting good heat from the dash vents and defroster then there's nothing wrong with the heater core. It's possible you have a problem with the blend door if the temp difference is that great. Do our cars use flexible ducting? Maybe the hose for the floor vents isn't connected?

 

So I've done some more messing around with this.

It seems like it'll vary with outside temp. I just remember a few weeks ago when it was a litte warmer out that it seemed to be operating almost like normal. In all modes. But when it's really cold outside then it's only mildly warm in the car if that.

A technician I work with suggested I try an AC delco tstat instead. What I had previously was just a cheap after market. So I just changed that tonight.

The engine seems to heat up normally, but just doesn't seem like its as warm as it should be in the cabin.

So I started just feeling hoses for the hell of it. I did notice that the upper heater hose was much warmer than the lower hose. It was hot.

Could that be a sign of heater core issues? Or should I flush the whole cooling system? Or is that just normal characteristics?