Question about 1989 GMC Sierra

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1989 GMC Sierra 1500 heater blows cold air. Changed thermostat. Both hoses are cold.

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  • GMC Master
  • 3,103 Answers

Check antifreeze level add if low, and check intake heat control valve on ps side of intake if its locked shut it can be removed and a water pipe nipple put in place of it and the heater hose reconnected..if the water pump is good, it should give heat this valve should be on the intake with a heater hose connected to it..and its vacuum operated but will jam shut with age and cold weather..good luck..

Posted on Jan 19, 2013

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Posted on Jan 02, 2017

OLDERQT
  • 1 Answer

SOURCE: 93 gmc sierra heater not working

THERMOSTAT REPLACE IF NOT SEE IF HOSES ARE CLOGGED SHOT OF AIR COULD HELP OR DISSCONNECT BATTERY CABLE 10-15 MIN CONNECT BACK TRY HEATER

Posted on Jan 04, 2009

  • 90 Answers

SOURCE: 2005 GMC Sierra Overheating

If your sure there is no trapped air in system after refill and air bleed off, is fan clutch pulling good air thru radiator? Even if it is, the heater should have coolant as hot as what temp gage is showing! Try backwards flushing heater core (dex cool is notorious for plugging these up). There is a TSB for cracked cylinder heads from GM for unexplained coolant loss.Remove drivers side valve cover, and look at center three head bolts for coolant around them, if coolant has been getting in thru this suspect area, there will be a milky/pudding like goo under valve cover and on head. GM had a company called Castec cast these and the areas near the head bolts were found to be too porous (NO recall YET!) Ya, you guessed it, replace heads! Unfortunately, if its gotten hot to many times, it has probably hurt the heads/gaskets. Hope this helps. PS: The castec logo is under the rearmost pair of rocker arms,may have to remove them to see.

Posted on Feb 05, 2009

  • 6 Answers

SOURCE: 2000 gmc sierra 1500 5.3 v8. a/c heater control problem

your heat/cool and vent selection options are controlled by engine vacuum through small clear tubes attached to the rear of your climate control interface. Other vehicles have small steel pull wires that operate the desired changes. You might try removing the trim and any fasteners affiliated with the interface/console. GENTLY pull outward and look to see if any of these tubes are pulled off or cut/damaged. Did anyone recently install a new stereo in the vehicle? If so, the vacuum tubing and or pull wires that change your outlets could have been damaged when the stereo unit was pushed into place. Hope this helps

Posted on Sep 09, 2009

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  • 1857 Answers

SOURCE: Heater blowing cold air changed thermostat still

you have a blend door actuator that may be bad. Its a little motor that can be a bear to swap out. Unless your pretty mechanically inclined and have the right tools you may want a shop to diagnose this to be sure.

Posted on Dec 29, 2009

  • 1509 Answers

SOURCE: 2004 gmc 1500 sierra heater control stuck on

Defrost is the default position. Is the control a autyomatic temperture control unit? ( you set the temp and select automatic) if it is the system is completely electronic. You push the buttons and the control still says defrost or can you select something else and the control shows it but it just keeps coming out the defrost? If the control changes and the air comes out the defrost anyway and the cheack engine light isn't on, then the problem can be blown fuses or an air door actoater not working. Does the dash emit a clicking sound? if it does with the covers off the bottom of the dash reach around touching the different pieces till you touch the idem that is clicking. this is an acutor motor, or blend door motor. they have gears in them that wear out and break the motors aren't repairable and you just replace the ofending motor. the door that is moves can be stuck. and may have to be freed up with blaster, WD40, or other rust buster till it moves easy. maybe after getting the door to move smoothly you can get the old motor to move the door wiithout having to install a new one.

Posted on Jan 06, 2010

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K so I have replaced all of the blend air motors and then also have changed out the thermostat on my 93 gmc sierra and also have changed heater core out and it still blows out cold air I can switch where...


Check to make sure the motors are moving hot to cold. The blinking control panel means it has self diag mode. Google how to get the heater control panel to go into self diag mode and when you get codes goggle them too . Prob bad control panel switch or unit

Oct 24, 2013 | 1993 GMC Sierra

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My 1989 GMC Sierra (350, 2WD) was leaking from the water pump and overheating...Installed new water pump and serpentine belt (after getting it off, it needed to be replaced)...Truck is still overheating,...


when replacing coolant, did you bleed the air from system! you can remove radiator or overflow cap when cold. start vehicle and let it run until thermostat opens,when all air is out hoses should get hot. but before starting, turn heater on to high setting, if you vehicle does not have a air bleeder on it. do as above. just be sure radiator is full of coolant. after hoses get hot, turn off heater, then put cap back on radiator or overflow. good-day! the first thing to do is to check for a stuck closed thermostat. do this first ok!


Jul 27, 2011 | 1989 GMC Sierra

1 Answer

Heater blowing cold air. like air cond. on. i changed thermostat


If the car is otherwise running fine, then the thermostat is almost never an issue. you need to take a look at the heater core and any heater valve stuck in a heater hose, that is where most of those issues are resolved.

Nov 18, 2010 | 1999 GMC Sierra

1 Answer

Heater blows cold


ok there is a few things might be happening...first did you make sure when you put the intake gaskets in there was No ports plugged or covered...second is...are both heater hoses Cold or is one hot and other cold...if so you have a air lock in the heater core...if this is the problem you need to lossen off the cold one till antifrezze comes out.

Mar 06, 2010 | 1989 GMC Sierra

1 Answer

I just changed thermostat, and replaced coolant, still my 1995 gmc suburban blows cold air.


Find the two heater hoses going through the firewall to the heater core both need to be hot at operating temp. If both are hot the problem will be inside with the heater control. I only one heater hose is hot the
problem will be the heater core. I am assuming you have bled all the air out of the cooling system.

Feb 25, 2010 | 1995 GMC Sierra

2 Answers

2005 GMC Sierra 1500 - heater blows, but only cold air


Check coolant level. Check for heat at the heater hose going from water pump to heater core at firewall. Check to see that cable is moving coolant control valve from the closed to open position. Low mileage so it shouldn't be plugged heater core.

Jan 07, 2010 | 2005 GMC Sierra

1 Answer

How do you vent air from the heater hoses?


take youre hose to your air conditioner and sut the take a cap like you use for pluming and rubber cement the cap on. thenwhen you get youre heater fixed all you have to do is take the cap of with channel locks

Jan 18, 2009 | 2000 GMC New Sierra 1500

1 Answer

2000 gmc sierra 5.3l heater does not get hot


After replacing the thermostat I pulled the heater hoses off and blew air through the heater core at firewall. Can only blow in left side as directional valves will prevent opposite. Chunks of stuff came out with coolant. I then put a piece of hose on the left side and shot water through until it came out clear.
Put it all back together and heat works fine.

Dec 31, 2008 | 2000 GMC New Sierra 1500

1 Answer

93 gmc sierra heater not working


THERMOSTAT REPLACE IF NOT SEE IF HOSES ARE CLOGGED SHOT OF AIR COULD HELP OR DISSCONNECT BATTERY CABLE 10-15 MIN CONNECT BACK TRY HEATER

Dec 20, 2008 | 1993 GMC Sierra

1 Answer

No Heat


You need to verify the blend door is operating and the heater core is not plugged or coolant flow to it is restricted.

Oct 29, 2008 | 1993 GMC Sierra

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