Heater not hot enough

[mieth]

Hi Everyone,
I have a 2005 Grand Prix SE, 105K miles, 3800 engine, manual temp control.
It is getting cold and the heater doesn't blow as hot as it did last winter, and I'll be in trouble when the Minnesota winter hits. I have replaced the thermostat, burped the coolant via the brass valve on the thermostat housing. The temp guage is consistent and steady approximately where it has always been. Car is not overheating. I have been reading thru related posts and have not found a solution. The hoses running to the heater core through the firewall are both very hot, so I don't think the heater core is blocked. The blower also works fine on all settings. Any suggestions appreciated.

[doctorhrdware]

It possible that the heater core fins are blocked with dust. This could cause the heat not to be as hot. Or maybe the heat control is not working correctly. This would also cause the heat not to be as hot.

[mieth]

Thanks for the suggestion, but I doubt that a 3 year old car would have an accumulation of dust such that it would affect the heater like this. I did read something in the forum about an actuator not moving to direct airflow through the heater core. Anybody have an idea about that? Also, what about the radiator cap? Could that be a factor here?

[tblake]

Is your cooling fan constantly on?

[mentel]

Thermostat!!

They are only about $10 and EASY as pie to replace.

Throw in a new thermostat. And if your winters are really cold throw in a 185!

If that does not work, you may be looking at lower intake manifold gasket or a slight head gasket leak, both of which should NOT occur with a vehicle that new, unless the coolant has never been replaced and it's bagged on!

[mentel]

Oops my apologies I did not read that you replaced the thermostat.
You should check for gasket leaks then on your intake manifold and cylinder head. If they are both fine then you could have issues with your heater core. Good luck!

[mieth]

Thanks for the responses.
The cooling fan does not run constantly. If the heater core were blocked, wouldn't one of the hoses running through the firewall be substantially cooler than the other? They are both about the same, and are very hot. I did read something in the forum about an actuator not moving to direct airflow through the heater core. Anyone know what that is?

[mentel]

Originally Posted by mieth

Thanks for the responses.
The cooling fan does not run constantly. If the heater core were blocked, wouldn't one of the hoses running through the firewall be substantially cooler than the other? They are both about the same, and are very hot. I did read something in the forum about an actuator not moving to direct airflow through the heater core. Anyone know what that is?

Actuator could be a solenoid.

You should get a tester and check out your electical system for your heating/cooling see if there is any voltage going through the different switches / solenoids. Kind of weird that your core is getting heat but it's not coming through the vents.

[BNaylor]

Originally Posted by mentel

Throw in a new thermostat. And if your winters are really cold throw in a 185!

If the winters are really cold why a 185 degree thermostat? The stock is rated at 195 degrees.

[tblake]

I was wondering the same thing Bob, but didn't want to open my big mouth if the stock temp on 04+ PG's was 180.

[richtazz]

Let's review here

Originally Posted by mentel

Thermostat!!

Throw in a new thermostat. And if your winters are really cold throw in a 185!

First off, a lower temp t-stat will cause lower heater output than the stock 195, as the coolant is regulated at a lower temp. The OP stated the t-stat was changed so this was a moot point (although you did catch yourself in a later post)

Originally Posted by mentel

If they are both fine then you could have issues with your heater core. Good luck!

The OP also stated in his first post that both heater hoses were very hot, so that would rule out a blocked heater core.

I would focus my energy on the temp door actuator. It's a fairly common issue, and sounds like the problem according to the symptoms.

[BNaylor]

Originally Posted by tblake

I was wondering the same thing Bob, but didn't want to open my big mouth if the stock temp on 04+ PG's was 180.

The alternate is 180 degrees but stock is 195 degrees which is the same as the '97-'03 models. The problem with running a 180 unless mods call for it or it is a SIII 3800 with supercharger with blower mods and evident KR is fuel economy may suffer because the engine may take longer to switch from open loop to closed loop mode especially if you live up North like you do and as the OP which looks like cold Minnesota. Also, a P0128 DTC may trip as a result since the 2000 and up PCM modules were modded to add this capability of monitoring. Plus in colder climates it may take longer for the transaxle to switch into overdrive - 4th gear due to the longer engine warmup times or improper thermostat regulating temperature.

In the case of the OP if the engine coolant temperature is correct as confirmed by the temp gauge at the IP and into and out of the heater core then a climate control unit issue may be worth looking at such as the temperature actuator. On the manual single zone you should see the lone temp actuator behind the glovebox and be able check its operation. The '04 and up models just like '97-'03 get some weird issues with the climate control system.

[mieth]

Thanks for all the responses.
I will check the actuator most likely on Thursday and post back my findings.

[BNaylor]

Just out of curiosity how is your weather where you live? Temps, etc. Do you feel no warm air out of the vents in any position or little after proper engine warmup time? Has the airflow changed any compared to the past? In other words do the blower speeds feel correct from low to high? The '05 Grand Prixs were supposed to be delivered with a cabin air filter so check that and make sure it is clean. Delco part number CF132. Less expensive aftermarkets are also available.

[mieth]

Minnesota this time of year starts out in the 30's in the morning, but warms up into the 50's, and we have a heatwave this week as its expected to hit 60. I checked the fan and it seems to ramp up speeds normally as the dial is turned. Warm air is output through all vents (dash, defrost, floor), but it is far short of where it normally gets. When we hit Winter, it will not be adequate.