flushed the heator core and worked for about a week and then same thing and when its hot out side it overheats i change the termostat and water pump wat else o ya i also cleaned the thing over the drivers head ambien thing or what ever what is the problom

 

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rriddle3 i have a problom and dont want you to be another what do you whant from me i dont know much about my wifes blazer besides it is taking a crap come on man is this all oyu have time to do is try and mess with people and sorry to anyone else who has to read this from rriddle3 i have a problom and want to try and get it fixed so please help

 

I think what Rich was saying is could you be more descriptive on what you have done... You say you cleaned the thing over the driver's head ambien thing... I believe that is what Rich was questioning... It is aweful hard for us to help you when you can't describe things well enough.

Anyway, have you flushed your coolant? I would recommend that you do a full flush on the system if you haven't yet done so. Even if you have, if the coolant looks even a little bit dirty, change it out.

Make sure that you have a new, working radiator cap. A failing or faulty radiator cap will not hold the required 16psi of pressure in the cooling system, making it boil over. This can also lead to air being in the system which could result in the lack of heat coming out of the heater core.

Some other tips, please include your vehicle information in your signature and attach it to all of your posts (these are both options in your profile). Also, please try to punctuate your posts. Simple periods go a long way in helping us read your posts and give you the advice you require. Anything that makes us be able to understand your situation better, helps you get the answers you seek as fast as possible.

 

ok sorry it is a 99 and i have changed the cap. when you sit in the driver seat theres a little round thing above your heat by the door someone told me it was for the climate control. dont know though. i have had everything flushed and new core from a local shop it only worked for a little bit after that. it only overheats when the air is on. and the vents blow out cold air all the time. if you turn it to heat and turn the fan off it still blows a little. not like it should. if you r sitting in the back you can feel it when its off. i hope this help i need to get it fixed before winter hits

 

Do you have automatic climate control where you set the temp and the truck does the rest? If you do, then it could be something with the control head, but if it isn't in auto mode, then you should still be able to force it to hot. That is unless it isn't a problem with one of the mode doors in the HVAC system.

On the overheating, have you made double sure that the radiator on the outside is clean? Sounds to me like the added heat from the A/C is causing the overheating which may be a sign of inadequate airflow through the radiator.

 

I've had this problem a couple times on my 2001 4x4. Took it in to the dealer, it was only 3 months after buying the thing, and they back flushed the heater core. If you had the heater core replaced, take it back to the shop as it should be under warranty.

Best solution is probably to back flush the heater core and flush out the rest ofyour coolantsystem at the same time.

 

yeah i agree with trying to back-flush the system...or there may be a lose of vacum at the heater box door, or a control cable may have come undone, depending on what your vehicle has. Also i think earlier you may have been refering to a 'Ambient Temperature Sensor, having one of those would indicate the vehicle has automatic temperature control