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I've had a 2005 Cobalt since it was new. I'm just joining today to see if anyone has any ideas about a problem with my heater. I wasn't quite sure which forum that best fits into?
 

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Wootsauce!
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I've had a 2005 Cobalt since it was new. I'm just joining today to see if anyone has any ideas about a problem with my heater. I wasn't quite sure which forum that best fits into?
Welcome to YC.com!

What seems to be the problem with your heater?
 

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Rocket Power
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Welcome to YC.com!
 

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Welcome to YC.com!

What seems to be the problem with your heater?
Thanks! The problem is that it seems to blow cold air only with the heater on and after running for nearly an hour.

Some background: About 2 months ago, it started doing this intermittently but when that happened, it would flip to hot after about 20 min. or so (and it would be a sudden change). It has been warm for the last few weeks with no return of this problem until last night. Then, it didn't change back to hot at all. Eventually, I was stopped for just a few minutes and came back and turned it on to find it was hot. When I turned the fan up, it went back to straight cold air and hasn't been back since (regardless of fan speed).

I checked the coolant level cold this morning and it is not low. Then after about a 45 min. drive it was still blowing cold air.

---------- Post added at 09:08 AM ---------- Previous post was at 09:07 AM ----------

welcome to our home! ya have any pics?
No, sorry. I don't really do pics much at all (not of myself either), so the only camera I even have is my cell phone camera (no flash on my Treo, either).
 

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Wootsauce!
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Thanks! The problem is that it seems to blow cold air only with the heater on and after running for nearly an hour.

Some background: About 2 months ago, it started doing this intermittently but when that happened, it would flip to hot after about 20 min. or so (and it would be a sudden change). It has been warm for the last few weeks with no return of this problem until last night. Then, it didn't change back to hot at all. Eventually, I was stopped for just a few minutes and came back and turned it on to find it was hot. When I turned the fan up, it went back to straight cold air and hasn't been back since (regardless of fan speed).

I checked the coolant level cold this morning and it is not low. Then after about a 45 min. drive it was still blowing cold air.

OK, well thats weird. Ummm, how many miles are on the car. What model Cobalt is it, LS, SS..??

Could be the thermostat. Are you getting any codes/engine lights.
 

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OK, well thats weird. Ummm, how many miles are on the car. What model Cobalt is it, LS, SS..??

Could be the thermostat. Are you getting any codes/engine lights.
It has around 90K miles, and it's an LS - 4 door if that matters. I'm not getting any messages, but as you might guess I don't have any type of computer that mechanics plug in to see more errors. The coolant temp that shows in the driver info screen has always been mid to upper 190's, but it was around 187-189 last night and this morning. To be fair, it has been cold outside (I live in Iowa) but it usually isn't quite that low even when it's been a bit colder outside (but 187 doesn't seem way off to me).
 

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iowa... Sounds like another snowcovered landscape to me.

1. Did you do ANY work under the hood, or any electrical work prior to this happening?-use ur noggin and remember!
2. Did any SHOP OR MECHANIC do any work or scheduled maintenance prior.....?

3. Does the vent knob route air properly? I.e.-feet, windshield, feet n cab, and cab?

*this isn't a faulty sensor or something electrical is it YC?-sounds like some kind of internal ac problem, like the hot air isn't getting routed to the vents (hopefully)
 

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Levee
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Ok, sounds to me like your heater core is plugged. Have you changed your coolant at all? If not, I would have your cooling system drained and flush the heater core. It's not a thermostat as the car would run really hot, or take a REALLY long time to heat up. It doesn't sound like anything electrical as you said it started intermitently. I'm going say I'm almost positive that it's your heater core being plugged.
 

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iowa... Sounds like another snowcovered landscape to me.

1. Did you do ANY work under the hood, or any electrical work prior to this happening?-use ur noggin and remember!
2. Did any SHOP OR MECHANIC do any work or scheduled maintenance prior.....?

3. Does the vent knob route air properly? I.e.-feet, windshield, feet n cab, and cab?

*this isn't a faulty sensor or something electrical is it YC?-sounds like some kind of internal ac problem, like the hot air isn't getting routed to the vents (hopefully)
Yes, plenty of snow... and it doesn't melt the next day like some places, it sits around until spring.

Here's the answer to your questions:
1. and 2. Just an oil change/tire rotation several weeks before at the Chevy dealer, and I personally replaced 2 turn signals (both rear and front left) since it started to occur intermittently.
3.Yes. When the blower is off, it seeps through wherever the vent knob is set but it has done that for as long as I can remember.

---------- Post added at 12:02 PM ---------- Previous post was at 11:53 AM ----------

Ok, sounds to me like your heater core is plugged. Have you changed your coolant at all? If not, I would have your cooling system drained and flush the heater core. It's not a thermostat as the car would run really hot, or take a REALLY long time to heat up. It doesn't sound like anything electrical as you said it started intermitently. I'm going say I'm almost positive that it's your heater core being plugged.
I guess I would have to check exactly when, but I think I have had at least 1 coolant flush since I've had this car... will check that and get back to you in a little while. How difficult would it be to clean the heater core? Is it something that is accessible without a whole lot of disassembly? Would it be prohibitively expensive to have the dealer do that?
 

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Levee
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I don't know about delta bodies, but they are easy on their predecessors, the J-bodies. All you have to do is disconnect the 2 coolant hoses that go into your firewall (make sure the coolant is drained before doing this to keep a LOT of coolant from going everywhere), and either take compressed air or a hose and go back and forth on the two metal hoses that go into the firewall into your heater core. Compressed air would be recommended as it has a LOT more pressure behind it, but water works too, just takes longer.
 

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Discussion Starter #15
Does anyone know where I can find a map of the engine compartment?

I called the dealer, and they said if it's the thermostat that it costs $500 to replace (not going to happen, then). I told them it was now around 187 for the coolant and they thought that's what it was.
 
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