No heat from heater?

I flushed the Heater Core and now have heat. This guide should help us fix it

https://www.2carpros.com/articles/car-heater-not-working

and this video

https://youtu.be/SNRb6pSwYuU

Let me know what you find.

I have the same problem with my 01 GMC Jimmy. little heat on low but it just seems that the inlet tot he heat core is hot and the outlet is warm. I thought the Water Pump may not be working but was going to look at the core first. Is it still working now that you have flushed the core?

Thanks for the help.

Yes, it is working fine. Give it a try..

Heater problem 6 cyl Two Wheel Drive Automatic 85000 miles

Last winter I went the whole winter without heat... very cold in Missouri. This winter I'd like to have heat in my truck. When I turn my heat on I only get air that is the same temp as the air outside. I've flushed my coolant system twice, changed the thermostat and I still haven't got the problem solved. I've been told that it might be the little device that adjust the vents from cool to warm air. I've torn apart my dash and can't find it. Can someone please help me?!?! I don't think i could bare another winter!!! Thanks.

Hey EMT...Paramedic here...My '94 s-10 has same problem...like you I was told a "little black control box" of some sort..Part is approx. $50. at Oreilly auto parts...and part is behind the radio somewhere...if I find or if u do i'll let u know and vice versa...good luck....flitemedic

Here is a guide that can help

https://www.2carpros.com/articles/car-heater-not-working

Please let us know what you find.

Cheers,

somebody else told me to take the heater hoses off that go to the heater core and hook a water hose to the intake side and flush just the heater core itself that solved my problem on my 2001 S 10

I would possibly check the heater core it may be blocked. Secondly the device is called a blend door actuator and can stick open or shut. Depending on if it opens or shuts depends on what air flow you get.

I've read through older posts of simalar issues, and I think I might have an 'air lock', of sorts, in the heater core....would like an opinion on how to fix this.

2001 S10 V6 4X4 P/U

Noticed a bubbling noise under the dash for the last two years. More prevalent when accelerating. I figured I had a plugged A/C drain and was hearing condensate slushing around in the housing. I never did find the drain, but my cousin, an S10 owner, said not to worry about it. I noticed this past Summer, it was draining A/C condensate as it should, so I assumed it fixed itself, as I no longer hear the 'sloshing sound'.
Well..... Now the heater barely puts out warm air.

One of the two hoses is hot, the other is cold, so it seems I'm not getting flow through the core. I traced both hoses down, looking for a "heater control valve" ...none found under the hood. The coolent level was down just above the ADD mark when cold. I've added about a pint and it hasn't gone down. I can't say it hasn't been low in the past. I always go to Midas for oil changes, so if they added any coolent and didn't tell me.....I'd have no way of knowing.

Anyone have an idea where to start?

Check the heater core if its clogged-up

Ya OK...That makes sense....Although, not what I wanted to hear as the hose is put up and the water lines to the garage are blowed-out for the Winter.

I assume you meant to try the water flush, as described elsewhere on this site? Right?

Might have to get this done by someone before Spring. :)

Thanks Much!

Before working on it, start the engine, allow the engine to warm up to operating temp with the heater on, and feel both heater core hoses. If both are hot, the core isn't plugged. If only one gets hot, then it is.

Alright, the last problem I was having with my truck was that I was not getting any heat at all from the vents. I flushed the system and it worked for a little while. Now what I'm noticing is that when I turn the heat on in my truck it kicks out COLD air, like A/C cold. the other day I popped the hood an noticed that the A/C compressor is engaged when I have the heat on. I'm confused my that one! Also my windshield tends to fog up when I'm driving in the moring. Any suggestions????

its normal to have the ac on in defrost mode .pressure test the coolant system to insure that your heater core is not leaking causing the fog on your windshield.check the hose going into the heater core they warm evenly as the engine warms

Hello - To better assist you can you tell me the size or your engine in liter and the 8th digit of your VIN. Okay.........do me a favor.............once the truck is at operating temperature check the heater hoses going into the firewall..........are they both hot.......the same temp or is one hot and the other cold. Next some of the common conditions for insufficient heating are as follows: 1. A leak in the cooling system. 2. A low coolant level. 3. A loose or worn drive belt. 4. A leaking or kinked heater hose. 5. A cracked or missing radiator cap seal. 6. A stuck thermostat 7. Temperature valve position As for the windshield fogging..........on the pic below.........many times our windshield fogs because we don't have outside air coming in.......therefore the inside air that is being blown (or not) fogs the windows.........there has to be air circulating..........

Depending on the outside temp and the inside of your car........lets say it is raining outside and hot..........you turn your AC on and the windows fog..........make sure it isn't on MAX A/C, number 3 arrow as your vent is closed off and you are not getting any outside air. You need to have it on number 4, 5, 6, 7, 8. Then your temp control number 2 is on full cold. If it is a little cool out or cold I guess make sure you have the temp control on whatever you need but the selector needs to be on again, 4,5,6,7,8. I say 4 because you will still get warm air though this selection still pulls outside air in.......... Try the above and let me know.............. For the heat.........please check to make sure your coolant is full.........replace the radiator cap, make sure your belt is properly tight and check the hoses as I asked and let me know.

My heater started blowing cold air yesterday morning. I noticed for a couple of weeks it didn't feel very warm. We have checked the passenger side under the dash for leaks and found nothing. The radiator is full and the water is getting hot. We also noticed that when we turn the AC on and then turn it back to heat that the blower seems to weaken...the air that comes out of the vents is stronger on the AC than the heat. Any ideas what it could be? I looked for the heater coil last night but can't find it anywhere. I took out the glove compartment and only saw a bunch of wires.

First i would like you to feel the heater core hoses and let me know if one is hot, neither are hot, both are hot, or if one is significantly cooler then the other, check directly by the firewall.

sounds to me that your blend door is functioning properly.

Had new air filter installed at dealership.

Now my heater does not work -- cold air only..

Could mechanic have disconnected something and not reconnected it ?

Engine temp reads within it's NORMAL range as usual.

I have a 2000 s10 that developed the same problem, heater just stopped working suddenly. I was thinking maybe a stuck thermostat valve or something, so I drained and flushed the cooling system to investigate, and a considerable amount of crud came out. I put in new antifreeze and after that the heater worked fine. Apparently the heater core intake had been clogged. Hope this helps.

my 2001 S-10 has no heat. I have plenty of anti-freeze, and it runs at 190 degrees. The temperature control knob seems to be working according to my muti-meter. thanks Tom

Check the thermostat and heater core if its clogged-up if okay could be an air mix/blend/mode door problem , vacuum and actuator and HVAC control module.

Heater problem
2001 Chevy S-10 6 cyl Four Wheel Drive Automatic
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When I turn on the heater or defrost blowing cold not hot..The air conditioner works fine and fan works fine,and the truck is not over heating..What am i looking at as far as the problem?? t/y

Mine was doing the same thing. Take off both heater hoses at the fire wall. use an air line to blow back thur the heater core. Mine had a lot of gunk in it that pluged it up.Blow into the return line to push it back out and not futher in.

there's seems to be a lot of listings of s-10 heater problems. my 2000 is no diferent. this winter it would only blow out of the top vents. Now with the warmer weather, i notice that i can no longer get warm air from anywhere. this is important now because of the cool mornings. and then later in the day when i want temperate a/c air, but now can only get freezing a/c air. the other posts seem to indicate that not much is every successful in correcting the S-10 heater problems. Do you have any proven successful suggestions.

When the air blows out of the defrost vents only, it's almost always a vacuum leak, or broken vacuum line from the engine into the heater control. Look for the Purple vacuum line that comes off the intake are, goes to t check valve, then to a vacuum reservoir, and into the car. If that's all good, use a hand vacuum pump, and see if all the servos under the dash hold vacuum. Steps to take by the book... INSUFFICIENT HEAT DIAGNOSIS 1. Perform HEATER OUTPUT TEMPERATURE CHECK . Go to next step. 2. Common conditions for insufficient heating are as follows:  A leak in the cooling system.  A low coolant level.  A loose or worn drive belt.  A leaking or kinked heater hose.  A cracked or missing radiator cap seal.  A stuck thermostat. Repair condition(s) as necessary and recheck heater operation. See HEATER OUTPUT TEMPERATURE CHECK . If heater system operates normally, system is repaired. If heater system does not operate normally, go to next step. 3. Turn ignition switch to ON position. Set mode control to floor/heat position. Set blower speed to HI position. Set temperature control to full hot position. If airflow from floor outlet is high, go to next step. If airflow from floor outlet is not high, go to step 7. 4. Move blower control through all positions. If blower speed changes, go to next step. If blower speed does not change, go to step 11. 5. Perform HEATER OUTPUT TEMPERATURE CHECK . If temperatures are as specified, go to next step. If temperatures are not as specified, go to step 12. 6. Inspect following areas of vehicle for cold air leaks and repair as necessary:  At cowl, below windshield.  Inside heater case, at door seals.  Inside outlet vent ducting. Perform HEATER OUTPUT TEMPERATURE CHECK . 7. Perform FUNCTIONAL TEST . If system operates as specified, repairs are complete. If system does not operate as specified, go to next step. 8. Check airflow from instrument panel vent outlets. If airflow from vent outlets is high, go to next step. If airflow from vent outlets is not high, go to step 17. 9. Move mode control to floor/heat position. A small amount of air should flow from defroster outlets. If airflow from defroster outlets is as specified, go to next step. If airflow from defroster outlets is not as specified, go to step 18. 10. Remove floor air outlet and check for obstructions. Remove or repair obstructions as necessary. Move blower control through all positions. If blower speed changes, go to step 9. If blower speed does not change, go to next step. 11. Check following components of blower motor controls and repair as necessary:  Blower motor switch  Blower motor resistor/relays  Blower motor system wiring harness Perform HEATER OUTPUT TEMPERATURE CHECK . If temperatures are as specified, go to step 6. If temperatures are not as specified, go to next step. 12. Turn temperature control to full hot position. Check temperature valve position. If temperature valve is fully closed, go to next step. If temperature valve is not fully closed, go to step 22. 13. With temperature control in full hot position, start engine and allow to idle. Check temperature of both inlet and outlet heater hoses. If temperature of air around each heater hose is about the same, 85 °F (24 °C), go to next step. If temperature of air around each heater hose is not the same, go to step 23. 14. Remove heater hoses at heater core and check that heater hoses are connected properly. If hoses are properly installed, go to next step. If hoses were not properly installed, go to step 25. 15. Backflush heater core and service cooling system. Reconnect heater hoses and refill cooling system. Start engine and bring it to normal operating temperature. Recheck temperature of both inlet and outlet heater hoses. If temperature of air around each heater hose is about the same, 85 °F (24 °C), go to next step. If temperature of air around each heater hose is not the same, go to step 23. 16. Replace heater core. See removal and installation procedures in appropriate HEATER SYSTEMS article. After heater core replacement, perform HEATER OUTPUT TEMPERATURE CHECK . 17. Set mode control to defrost position. Check airflow from defroster outlet. If there is little or no airflow, go to next step. If airflow is okay, go to step 10. 18. Move blower control through all positions. If blower speed changes, go to next step. If blower speed does not change, go to step 11. 19. Check for obstructions at blower motor inlet and at plenum. Repair as necessary. If obstruction was found, go to HEATER OUTPUT TEMPERATURE CHECK . If obstruction was not found, go to next step. 20. With blower motor set to HI position, move temperature control from full hot position to full cold position. If change in airflow is present, go to next step. If change in airflow is not present, go to step 26. 21. Check for restrictions between heater case and instrument panel outlets. Repair as necessary. Go to HEATER OUTPUT TEMPERATURE CHECK . 22. Re-index cable or actuator. Inspect temperature valve, cables, and linkage adjustment. Repair or replace as necessary. After repairs, perform HEATER OUTPUT TEMPERATURE CHECK . 23. Check thermostat for proper installation. If thermostat is properly installed, go to step 27. If thermostat is not properly installed, go to next step. 24. Reinstall thermostat properly and go to step 13. 25. Reinstall hoses to proper positions and go to step 13. 26. Inspect the following components and repair as necessary:  Temperature valve  Control assembly  Blower motor wiring harness Go to HEATER OUTPUT TEMPERATURE CHECK . 4/12/2010 ... Temp check: HEATER OUTPUT TEMPERATURE CHECK 1. Remove radiator cap when engine is sufficiently cool. Select heater (floor) mode, high temperature setting and high blower speed. Idle engine until coolant can be seen flowing in radiator. Install radiator cap. 2. When engine is warm, after about 20 minutes, drive vehicle at 30 MPH (48 km/h). Measure ambient air temperature and center vent outlet air temperature using a thermometer. If center vent air temperature exceeds minimum specification, heater output temperature is considered sufficient. See HEATER OUTPUT MINIMUM TEMPERATURE SPECIFICATIONS table.

Temp knob not working: TEMPERATURE CONTROL INOPERATIVE 2000 Models 1. Perform BLOWER CONTROLS SYSTEM CHECK . Go to next step. 2. Check HVAC I fuse (10-amp) located in instrument panel fuse block. If fuse is blown, go to step 21 . If fuse is okay, go to next step. 3. Disconnect air temperature valve sensor and motor connector. Air temperature valve is located on top of HVAC assembly, on passenger's side. Turn ignition switch to ON position. Turn headlight switch to PARK position. Using DVOM connected to ground, probe air temperature valve motor harness connector terminal No. 8 (Light Blue wire). See WIRING DIAGRAMS . Move temperature control knob on A/C-heater control panel to hot (Red) and cold (Blue) positions. If voltage reading varies smoothly between zero and 12 volts, go to next step. If voltage reading does not vary smoothly between zero and 12 volts, go to step 9 . 4. Using DVOM connected to ground, measure voltage at air temperature valve motor harness connector terminal No. 10 (Brown wire). If battery voltage is indicated, go to next step. If battery voltage is not indicated, go to step 7 . 5. Using DVOM, measure voltage between air temperature valve motor harness connector terminals No. 10 (Brown wire) and No. 7 (Black wire). If battery voltage exists, go to next step. If battery voltage does not exist, go to step 8 . 6. Replace air temperature valve motor. See AIR TEMPERATURE VALVE ACTUATOR under REMOVAL & INSTALLATION. Perform BLOWER CONTROLS SYSTEM CHECK . 7. Repair open or high resistance in Brown wire between instrument panel fuse block HVAC I fuse and air temperature valve actuator. Perform BLOWER CONTROLS SYSTEM CHECK . 8. Repair open or high resistance in Black wire between air temperature valve actuator and ground G200. Ground G200 is located on firewall, left of instrument panel, near main harness connector to engine compartment. Perform BLOWER CONTROLS SYSTEM CHECK . 9. If voltage reading is at or near battery voltage, regardless of temperature control knob position, go to next step. If voltage reading is not at or near battery voltage, regardless of temperature control knob position, go to step 15 . 10. Disconnect A/C-heater control panel 3-pin harness connector C-3. Use a DVOM to measure voltage between A/C-heater control panel 3-pin harness connector C-3 terminals "A" (Brown wire) and "C" (Black wire). Turn ignition switch to ON position. Turn headlight switch to PARK position. If battery voltage is indicated, go to next step. If battery voltage is not indicated, go to step 12 . 11. Replace A/C-heater control panel. See A/C-HEATER CONTROL PANEL under REMOVAL & INSTALLATION. Perform BLOWER CONTROLS SYSTEM CHECK . 12. Move headlight switch to OFF position. If DVOM reading changes to battery voltage, go to next step. If DVOM reading does not change to battery voltage, go to step 14 . 13. Repair high resistance in Black wire between splice pack SP203 and ground G203. SP203 is strapped to instrument panel harness, in front of ashtray. Ground G203 is located in body harness, to right of instrument panel, on firewall below air inlet. Perform BLOWER CONTROLS SYSTEM CHECK . 14. Repair open or high resistance in Black wire between A/C-heater controller and splice pack SP203. Perform BLOWER CONTROLS SYSTEM CHECK . 15. If voltage reading is at or near zero voltage, regardless of temperature control knob position, go to next step. If voltage reading is not at or near zero voltage, regardless of temperature control knob position, return to step 10 . 16. Disconnect A/C-heater control panel 3-pin harness connector C-3. Using Connector Test Adapter Kit (J 35616-A), connect jumper wires between connector C-3 and A/C-heater control panel terminals. Using a DVOM connected to ground, backprobe A/C-heater control panel 3- pin connector C-3 terminal "B" (Light Blue wire). Turn ignition switch to ON position. Turn headlight switch to PARK position. Move temperature control knob on A/C-heater control panel to hot (Red) and cold (Blue) positions. If voltage reading varies smoothly between zero and 12 volts, go to next step. If voltage reading does not vary smoothly between zero and 12 volts, go to step 18 . 17. Repair open or high resistance in Light Blue wire between A/C-heater control panel and air temperature valve actuator. Perform BLOWER CONTROLS SYSTEM CHECK . 18. Use a DVOM to backprobe between A/C-heater control panel 3-pin connector C-3 terminals "A" (Brown wire) and "C" (Black wire). If battery voltage exists, go to step 23 . If battery voltage does not exist, go to next step. 19. Using a DVOM connected to ground, backprobe A/C-heater control panel 3-pin connector C-3 terminal "A" (Brown wire). If battery voltage is indicated, return to step 11 . If battery voltage is not indicated, return to step 7 . 20. Check HVAC 1 fuse No. 21. If fuse is okay, go to next step. If fuse is faulty, go to step 22 . 21. Repair short to ground in Brown wire between instrument panel fuse block and A/C-heater control panel harness connector C3 terminal "A". Perform BLOWER CONTROLS SYSTEM CHECK . 22. Repair open in Light Blue wire between instrument panel fuse block and ignition switch. After repair, perform BLOWER CONTROLS SYSTEM CHECK . 23. Disconnect jumper wire from connector C-3 terminal "B" (Light Blue wire). With jumper wire still connected to A/C-heater control panel, use a DVOM to measure voltage between jumper wire and ground. Disconnect air temperature valve actuator connector. Move temperature control knob on A/C-heater control panel to hot (Red) and cold (Blue) positions. If voltage reading varies smoothly between zero and 12 volts, go to next step. If voltage reading does not vary smoothly between zero and 12 volts, go to step 11 . 24. Repair short to ground in Light Blue wire between A/C-heater control panel harness connector C3 terminal "B" and air temperature valve actuator. After repair, perform BLOWER CONTROLS SYSTEM CHECK . 4/12/2010 ...

I get no heat when I turn on the defroster. I get some heat (not as hot as it used to be) when I switch to the passenger setting but when I switch back to defrost the heat goes away and very cold air blows out the defroster. ??????

Welcome to the site. As far as cold air coming out the defrost, might be a problem with a directional door/actuator? With the air not being as hot, you feel of the heater hoses, see if both are hot? Maybe a problem with the heater core or thermostat issue?

no heat

Check the heater hoses to see if they are getting hot.Those S-trucks used Dexcool which tended to plug up the heater cores. If hoses are not hot, then haev the heater core backflushed to clear it out.If hot, then you probably havea blend door actuator problem or a bad control head

Heater problem
2000 Chevy S-10 4 cyl Two Wheel Drive Manual

Regardless of dial selection, no heat,

need more information. Does the fan work? Does the temp guage go up when car ihas been running for a while? What does it do? The problem can be anywhere from a bad thermastat, a clogged heater core , lack of coolant, or to bad heater controls.

New thermostat, radiator full, upper radiator hose hot, A/C seems to b cold. Any ideas??

Heater hoses hot? Move the temp control selector around and see if the cables to the blend doors are moving properly on the airbox (under the dash). Listen for the blend doors moving inside the box.

Heater hoses not hot, little warm, can hear change n box when changing temp.? Core bad or maybe plugged??

Is there a valve near the bulkhead before the core? If so, my guess would be it. If not, the core.

Not exactly sure what a bulkhead is, would it b n engine compartment on firewall or n/under dash?

Ah-ah-ah.....naughty naughty. Firewall is no longer a legal word to use in conjunction with automobiles since they don't stop fire, or really even slow then down. It is now, legally, a bulkhead. Us old fogies know it and love it (hate it?) as a firewall.

But, yeah, that metal wall separating passenger and engine compartments. If it has a heater control valve, it should be just inside the engine compartment on one of the heater hoses.

Well no valve, so im looking at the core right? Would flushing it maybe help?, its not driven a whole lot as u can tell by the mileage?

It should. Use something like Prestone, drain it, then use pressurized water to flush it.

I'll give it a shot flushing it, thank u very much for your time and advice, hope this works, thanks again!

Have a safe and happy new year!