98 blazer heater issue

aircrewman · 01-23-2007, 08:39 PM

97/98 4dr 2wd ls blazer. I can change the temp from cold to hot on the temp selector but it only blows warm air not hot, this is wiith the engine temp at 180. That is as high as the engine temp will go. also when I select the different zones i.e. head, head and floor, or defrost. the doors in the ducting never switch to blow air out of the floor ducts, it only cycles to head and defrost, when floor is selected it blows lightly out the defrost vents. anyone have any ideas? I was thinking heater core but those usually leak when they go bad and my floor is dry as a bone..

FireCat595 · 01-26-2007, 01:57 PM

the thermostat opens at 195 degrees fairenheit, and when the thermostat opens it usually makes the heat hotter. maybe your coolant mix isn't right. if you have either not enough water or to much water it will not let the engine heat up enough. check your mixture it could be the problem.

aircrewman · 01-26-2007, 03:53 PM

Quote: Originally Posted by FireCat595

the thermostat opens at 195 degrees fairenheit, and when the thermostat opens it usually makes the heat hotter. maybe your coolant mix isn't right. if you have either not enough water or to much water it will not let the engine heat up enough. check your mixture it could be the problem.

Sweet, I noticed that the guy who owned it prior to me put green antifreeze in it, it should have dexcool, so I'll change that out and see if it works. thanks man....

lummy · 01-26-2007, 05:37 PM

Quote: Originally Posted by aircrewman

Sweet, I noticed that the guy who owned it prior to me put green antifreeze in it, it should have dexcool, so I'll change that out and see if it works. thanks man....

Nah.. you're better off (IMO) with the green stuff. A lot of people, myself included, have had issues when using dexcool. Do a search for dexcool and read some of the nitemares.

If you're going to change coolant, do a really good flush too. If the previous owner didn't flush out all the dexcool, it could be clogging up the heater lines.

menotyou · 01-26-2007, 06:15 PM

Ok sounds like you may have two seperate problems. First no heat, second the air is not getting directed properly.

No heat...If you engine reaches 180 degrees you should get some heat out of the vents, by no means should blow cold. Two maybe three possibilities.

First that the heater core is plugged, this tends to happen on the s-series trucks when the po mixes dexicool and green antifreeze, also occurs more readily with high levels of h2o or with low levels in the coolant overflow tank. Insure that both heater hoses are getting warm, if one is not getting warm then you know that there is a lack of flow through the core. To fix do a reverse flush of the heater core. Try to be careful as to not apply to much pressure because the core can be sensitive and rupture, you do not want this to happen as the core is very hard to get to.

Second. I have not looked at my 95 but most vehicles come with a heater control valve in the feed line to the core. If this is not opening then you will not get hot water running through the core. Some manufactures use electric valves while others use cable operated ones.

Third. If all is working as it should be then the door that opens and shuts off the heater core from the rest of the climate control system could be malfunctioning and stuck closed.

As far as the vents not opening up that is dependent on if the truck uses vacuum or electric operated servos as to what the problem could be. I would hazard a guess that the servos are electric. Defrost is the default safety setting on most vehicles. If there is not the proper signal coming out of the switches then the servo for the defrost vent automatically relaxes opening up.

I hope this gives you some direction as to where to start looking. Good Luck.

aircrewman · 01-26-2007, 07:46 PM

I think its a clogged heater core, I added some water and removed some antifreeze and the thermostat opened up and the heat got alittle warmer but as soon as I drove it it went cool again, and by cool I mean a little warmer than the ambient air. I touched the inlet heater hose under the hood ( the large line) and it was hot, then I touched the outlet and it wasn't as hot, so I think I am going to have to back flush the heater core tomarrow and see if that works,

As far as the vaccum thing I am going to take a look at what you said as well, thankyou for the info, I should be able to figure this out from just that alone. thanks again...

01-23-2007, 08:39 PM	#1
aircrewman AM1 (AW/NAC) P-3's Age: 32 Join Date: Jan 2005 Posts: 514 Location: Orange park, FL User is: OffLine	98 blazer heater issue 97/98 4dr 2wd ls blazer. I can change the temp from cold to hot on the temp selector but it only blows warm air not hot, this is wiith the engine temp at 180. That is as high as the engine temp will go. also when I select the different zones i.e. head, head and floor, or defrost. the doors in the ducting never switch to blow air out of the floor ducts, it only cycles to head and defrost, when floor is selected it blows lightly out the defrost vents. anyone have any ideas? I was thinking heater core but those usually leak when they go bad and my floor is dry as a bone..
	[Reply w/Quote]

01-26-2007, 01:57 PM	#2
FireCat595 Flat Black Chevy Join Date: Aug 2006 Posts: 155 Location: Verona NY User is: OffLine	Re: 98 blazer heater issue the thermostat opens at 195 degrees fairenheit, and when the thermostat opens it usually makes the heat hotter. maybe your coolant mix isn't right. if you have either not enough water or to much water it will not let the engine heat up enough. check your mixture it could be the problem.
	[Reply w/Quote]

01-26-2007, 03:53 PM	#3
aircrewman AM1 (AW/NAC) P-3's Age: 32 Join Date: Jan 2005 Posts: 514 Location: Orange park, FL User is: OffLine	Re: 98 blazer heater issue Quote: Originally Posted by FireCat595 the thermostat opens at 195 degrees fairenheit, and when the thermostat opens it usually makes the heat hotter. maybe your coolant mix isn't right. if you have either not enough water or to much water it will not let the engine heat up enough. check your mixture it could be the problem. Sweet, I noticed that the guy who owned it prior to me put green antifreeze in it, it should have dexcool, so I'll change that out and see if it works. thanks man....
	[Reply w/Quote]

01-26-2007, 05:37 PM	#4
lummy Registered User Age: 42 Join Date: Jan 2007 Posts: 123 Location: User is: OffLine	Re: 98 blazer heater issue Quote: Originally Posted by aircrewman Sweet, I noticed that the guy who owned it prior to me put green antifreeze in it, it should have dexcool, so I'll change that out and see if it works. thanks man.... Nah.. you're better off (IMO) with the green stuff. A lot of people, myself included, have had issues when using dexcool. Do a search for dexcool and read some of the nitemares. If you're going to change coolant, do a really good flush too. If the previous owner didn't flush out all the dexcool, it could be clogging up the heater lines.
	[Reply w/Quote]

01-26-2007, 06:15 PM	#5
menotyou Registered User Age: 29 Join Date: Jan 2007 Posts: 42 Location: User is: OffLine	Re: 98 blazer heater issue Ok sounds like you may have two seperate problems. First no heat, second the air is not getting directed properly. No heat...If you engine reaches 180 degrees you should get some heat out of the vents, by no means should blow cold. Two maybe three possibilities. First that the heater core is plugged, this tends to happen on the s-series trucks when the po mixes dexicool and green antifreeze, also occurs more readily with high levels of h2o or with low levels in the coolant overflow tank. Insure that both heater hoses are getting warm, if one is not getting warm then you know that there is a lack of flow through the core. To fix do a reverse flush of the heater core. Try to be careful as to not apply to much pressure because the core can be sensitive and rupture, you do not want this to happen as the core is very hard to get to. Second. I have not looked at my 95 but most vehicles come with a heater control valve in the feed line to the core. If this is not opening then you will not get hot water running through the core. Some manufactures use electric valves while others use cable operated ones. Third. If all is working as it should be then the door that opens and shuts off the heater core from the rest of the climate control system could be malfunctioning and stuck closed. As far as the vents not opening up that is dependent on if the truck uses vacuum or electric operated servos as to what the problem could be. I would hazard a guess that the servos are electric. Defrost is the default safety setting on most vehicles. If there is not the proper signal coming out of the switches then the servo for the defrost vent automatically relaxes opening up. I hope this gives you some direction as to where to start looking. Good Luck.
	[Reply w/Quote]

01-26-2007, 07:46 PM	#6
aircrewman AM1 (AW/NAC) P-3's Age: 32 Join Date: Jan 2005 Posts: 514 Location: Orange park, FL User is: OffLine	Re: 98 blazer heater issue I think its a clogged heater core, I added some water and removed some antifreeze and the thermostat opened up and the heat got alittle warmer but as soon as I drove it it went cool again, and by cool I mean a little warmer than the ambient air. I touched the inlet heater hose under the hood ( the large line) and it was hot, then I touched the outlet and it wasn't as hot, so I think I am going to have to back flush the heater core tomarrow and see if that works, As far as the vaccum thing I am going to take a look at what you said as well, thankyou for the info, I should be able to figure this out from just that alone. thanks again...
	[Reply w/Quote]