Heater not working

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  #1  
Old 10-07-08, 01:05 PM
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Heater not working

I have a 99 Chevy S10 pickup. The blower works, but there is no heat. Anyone have any suggestions as to what it might be? Thanks
 
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  #2  
Old 10-07-08, 02:25 PM
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Feel the two coolant hoses going into the firewall. They both should be pretty warm/hot. If one is hot, the other cold, you got a clogged heater core which needs to be flushed.

If both are hot/warm, it could be one of the following:

1. Blend door malfunction
2. Vacuum line issue (if not electronic)
3. Control panel.
 
  #3  
Old 10-07-08, 05:22 PM
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I agree, these things are notorious for clogged/restricted heater cores. Also, if the core is indeed plugged, pop the radiator cap off when the vehicle is cool enough to do so and look to see if there is any build up in the radiator. You may be in need of a radiator/coolant flush if so. Otherwise, the core will just plug up again eventually. You will need to get all the crud out of the system.
 
  #4  
Old 10-07-08, 07:23 PM
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don't forget the first thing to check is it full of coolant? low coolant level is probably the number one reason for lack of heater output. other wise hot is leading you right.

life begins when the kids leave home and the dog dies
 
  #5  
Old 10-07-08, 10:16 PM
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dont forget

Lets not forget the valve that diverts fluid into the heater core it might be stuck closed not allowing water in. Not sure on a chevy if it is a cable or vaccumm operated device.
I would check that before any heater core surgery.
 
  #6  
Old 10-09-08, 04:22 AM
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Most definitely check the heater control valve under the hood that is in-line with the heater hose going to the heater core. A lot of them are vacuum controlled and a loss of vacuum at that valve will cause it not to open. Also use a hand held vacuum to test it as well. I have seen the diaphragm dry rot and leak causing it not to open.

Also on some of the heater valves you can actually see if it is opening and closing. You will see a rod or linkage on one end. Just switch it from hot to cold and note and differences. Here is an example...

 
  #7  
Old 10-09-08, 06:46 PM
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This vehicle does not have a valve.
 
  #8  
Old 10-09-08, 10:11 PM
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found this

ACDELCO Part # 155372 {#22532158}
Category: Heater Control Valve.
It does not look like a valve but a thermostat of some sort that lets hot water in.
Also check that vacuum can under the hood it should look like a big plastic ball with a couple of hoses going to it it would run your blend doors.
 
  #9  
Old 10-15-08, 05:37 PM
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The coolant nipple has a valve in it? I'll be damned. All the ones I've seen are just a wide open fitting.



 
  #10  
Old 10-15-08, 07:09 PM
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He hasn't responsed yet to my question about the hoses, so that would determine this "valve" is operational.

On a side note, I've never seen one of those valves before..
 
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