2000 Blazer Heating Problem

I have a 2000 model Blazer w/ the Trailblazer package. I am having trouble with getting heat into the cabin. The Blazer has the computer climate control system installed. The temp gauges reads normal, in the same area it has been since i bought it new, so I suspect the thermostat is fine. When I turn the heater on, at best only luke warm air flows out the vents. Even when using the recirc button, the system doesnt seem to be putting out heat like it should, last year it was hot enough for one to sweat when driving. The fluid levels in the radiator have always been check frequently and have never dropped low.
I suspect a problem with either the control itself of the regulator that controls the amount of fresh air entering through the heater core, but I dont know how to check either.

Any ideas

Thanks for your help

When you turn it to cold, do the air coming out the vents get colder?

BlazerLT is looking at it from the vacuum perspective to see if the door is actually moving. Once you determine that, the next question will be have you had the coolant flushed yet? If you haven't, you are due. If you have over the past year you can have one of two problems. The heater core is either restricted (which can happen after a flush) or there is an air pocket in the heater core. After the truck has been running for a bit, shut the truck off and reach down behind the engine by the firewall and feel each of the heater hoses going into the heater core. Both should be really warm. If one is warm and the other cooler or cold, your heater core is not flowing properly and needs to be backflushed. The dealer ended up back flushing mine with a pressure washer to clean the crap out as it clogged after they did a flush and fill. If it is flowing freely, I would suspect an air pocket. Remove the rad cap and let it run for a bit to try and work out the bubble. I have not bled mine before so I'm not sure if there is a bleed nipple on these years for the cooling system. Once you get this all worked out, do a search on DEXCOOL and RAD CAP and get your rad cap replaced with an aftermarket.

Yip, cooling system and heater core will need a complete reverse flush and refill.

Then replace your stock rad cap with a cap other than the AC Delco variety.

The stock caps are prone to failure.

Yeah my 2000 Blazer had a problem with the heat only working for a few minutes and then nothing but cold air coming out after that. When I flushed mine the other day, my heat started working again. Although my reservoir is going dry like every 4 days and I cant find a leak though, but that is another problem for another thread! =)

Yeah my 2000 Blazer had a problem with the heat only working for a few minutes and then nothing but cold air coming out after that. When I flushed mine the other day, my heat started working again. Although my reservoir is going dry like every 4 days and I cant find a leak though, but that is another problem for another thread! =)

That is because the air is being worked out of the system, expect to refill the resevoir a couple times as the new coolant displaces the air.

Make sure you fill the radiator too. It will take a long time to work the air out if you only fill the reservoir. Also make sure your new stant cap is on straight and tightened all the way. I usually have to top mine off 3 or 4 times before it holds steady. Remember the reservoir should be at the full mark when hot, it will be around the add mark when cold. If you fill it up cold, when the engine warms up it will push out the extra.

Make sure you fill the radiator too. It will take a long time to work the air out if you only fill the reservoir. Also make sure your new stant cap is on straight and tightened all the way. I usually have to top mine off 3 or 4 times before it holds steady. Remember the reservoir should be at the full mark when hot, it will be around the add mark when cold. If you fill it up cold, when the engine warms up it will push out the extra.

Hehe, yea, I found that out too.

Stopped the truck, went in the store, came out, and had a stream of coolant running out of the coolant overflow hose.

Scared me for a second and then I realized I did overfill it a bit.:D

Hehe, yea, I found that out too.

Stopped the truck, went in the store, came out, and had a stream of coolant running out of the coolant overflow hose.

Scared me for a second and then I realized I did overfill it a bit.:D

yeah, it will scare the sh!t out of you when you come out and there's something leaking under your truck. :)

hehe, yea, I was like "OH NO, I GOT AN OIL LEAK!" EEEEK!

But the system displaced the extra like it is supposed to and ever since, everything has been peachy.

Yes the air gets colder when moving the temp selector to cold

BlazerLT is looking at it from the vacuum perspective to see if the door is actually moving. Once you determine that, the next question will be have you had the coolant flushed yet? If you haven't, you are due. If you have over the past year you can have one of two problems. The heater core is either restricted (which can happen after a flush) or there is an air pocket in the heater core. After the truck has been running for a bit, shut the truck off and reach down behind the engine by the firewall and feel each of the heater hoses going into the heater core. Both should be really warm. If one is warm and the other cooler or cold, your heater core is not flowing properly and needs to be backflushed. The dealer ended up back flushing mine with a pressure washer to clean the crap out as it clogged after they did a flush and fill. If it is flowing freely, I would suspect an air pocket. Remove the rad cap and let it run for a bit to try and work out the bubble. I have not bled mine before so I'm not sure if there is a bleed nipple on these years for the cooling system. Once you get this all worked out, do a search on DEXCOOL and RAD CAP and get your rad cap replaced with an aftermarket.

I have never had the cooling system flushed as of yet, the manual recommended 100,000 miles for that but apparently that is too long too wait. I have check both hoses and one is quite warm, the other is cold to the touch. Thanks for the help, I have the system back flushed and and refilled with fresh juice, also I will replace the cap. Hopefully I will have heat before the winter is over.

As swalt posted above, have you checked to see if the two smaller coolant hoses running into the firewall are both very warm? If there is a noticable difference between the temperature of the two, then the heater core may be plugged and may need a reverse flush, as BlazerLT mentioned.

Edit: You replied before I finished replying, so I didn't see your last reply. So ignore mine http://www.automotiveforums.com/vbulletin/images/icons/icon7.gif

Hehe, people are so quick responding today. :D

As swalt posted above, have you checked to see if the two smaller coolant hoses running into the firewall are both very warm? If there is a noticable difference between the temperature of the two, then the heater core may be plugged and may need a reverse flush, as BlazerLT mentioned.

Edit: You replied before I finished replying, so I didn't see your last reply. So ignore mine http://www.automotiveforums.com/vbulletin/images/icons/icon7.gif

Hey I have heat again, I still have to get the system flushed but....I disconnected the hoses going into the heater core thinking I would swap em to let the system backflush itself. GM was smarter than that, the hoses are different sized.
Anyway, once the pressure was relieved to the heater core, I reconnected the hoses in their original postion, and to my amazement, I have heat now :)

Still go get the system flushed and replace the rad cap with something that is NOT AC Delco.