Question about 1989 GMC Sierra

1 Answer

I would like to know how I can fix the heater in a 89 gmc k1500 with a 350 engine and no air. I tried a new heater motor and still not working. The Fuse is also good.

Posted by on

Ad

1 Answer

  • Level 3:

    An expert who has achieved level 3 by getting 1000 points

    Top Expert:

    An expert who has finished #1 on the weekly Top 10 Fixya Experts Leaderboard.

    Superstar:

    An expert that got 20 achievements.

    All-Star:

    An expert that got 10 achievements.

  • GMC Master
  • 5,332 Answers

This is a blower motor not working tip I posted a little while back.

Blower motor problems are a pretty common topic. This is a basic guide on how to diagnose the problem and will work for most vehicles.

The diagram is generic and loosely based on GM's setup and more specifically a Silverado. Most manufacturers have a similar setup and the only major differences would be a ground side control (instead of the switch supplying power to the resistor it would be grounding the power from the resistor if this is the case you test light would need to be connected to power to test the switch) and late model Chrysler minivans (they use a module that looks for a difference in a/c voltage from the switch)

If the blower works on high only than likely the resistor assembly is the culprit since power to the blower essentially bypasses all of the resistors and/or the resistor assembly entirely. The reason why none off the other speeds will work is that the resistor or the circuit for the speed four setting has burned out. The lower the setting the more resistance you need to drop the voltage to the blower. The first speed setting requires all four resistors to drop the voltage enough to turn the blower at its slowest speed. Speed 2 needs to turn the blower a little faster so it uses three resistors. Speed 3 uses two resistors and speed 4 uses one.

In some cases the fan will work on high and speed setting 4. The likely cause for this is the speed 3 resistor or circuit has burned out. Speed 4 still works because it doesn't use the lower speeds resistors to control the speed of the blower. If the speed 2 resistor burns out than speed 1 and 2 will not work but 3, 4 and high will continue to work. If the speed 1 resistor burns out than speeds 2, 3, 4, and high will continue to work.

This leads us to how do we know if its the resistor or the switch or the blower. If the blower works on high than we know the blower works. That leaves us with either the switch or the resistor assembly (there are many other possibilities) which can be easily tested with a test light (or a voltmeter if you choose) The first thing to do is locate the resistor assemble. They can be behind the glove box, under the dash close to the blower motor or under the hood, again usually close to the blower motor. It will typically have 5 to six wires going to it. We'll start by unplugging the connector, turning the key on and connecting your test light to ground.

1.Turn the switch to high and backprobe all the wires. Two of them should illuminate the test light. In the diagram below this would be wire E & F. If you don't have a diagram then hold the test light on one of the two wires and move the switch to another speed setting. the wire that continuously illuminates the test light regardless of the switch position will be the constant power for high blower speed and will not need to be rechecked in the following steps.

2. Turn the switch to the next lowest setting. Backprobe the remaining wires to see if one of them illuminates the test light. Repeat until you have checked all of the speed settings.

3. If the test light has illuminated a different wire for each setting then we can reasonably assume that the switch is functioning as intended and the source of the problem is the blower resistor.

If you find one or more settings (but not all the settings) on the switch that does not illuminate the test light on any wire than we can reasonably assume that the switch has failed.

There are a few other things that can cause blower motors not to work as intended. The switch or the resistor assembly are the two most common problems.

I would like to know how I can fix the heater in a - 342697e.jpg

Posted on Nov 09, 2010

Testimonial: "Thanks for the high speed answer! Haven't tried using these suggestions yet, but appreciate the help all the same. Thanks again"

Ad

1 Suggested Answer

6ya6ya
  • 2 Answers

SOURCE: I have freestanding Series 8 dishwasher. Lately during the filling cycle water hammer is occurring. How can this be resolved

Hi,
a 6ya expert can help you resolve that issue over the phone in a minute or two.
best thing about this new service is that you are never placed on hold and get to talk to real repairmen in the US.
the service is completely free and covers almost anything you can think of (from cars to computers, handyman, and even drones).
click here to download the app (for users in the US for now) and get all the help you need.
goodluck!

Posted on Jan 02, 2017

Ad

Add Your Answer

Uploading: 0%

my-video-file.mp4

Complete. Click "Add" to insert your video. Add

×

Loading...
Loading...

Related Questions:

1 Answer

When i get in my jimmy to go to work its blowing hot air( with the heater on of course) and then there is a creaking noise coming from the blower motor area, then the heater will start blowing cold air...


Because the Main Gear in the Blend Motor has cracked or teeth have chipped and is now not keeping the heat/cold door to the Hot position. 3 fixes: Buy a new Blend motor, takes about 5mins to replace. Buy a new Blend Motor Gear, will take about 30mins to fix. Repair current gear with Epoxy, takes about 30mins and 12hrs for the glue to set up strong enough to use it.

Feb 24, 2011 | 1998 GMC Jimmy

2 Answers

I have a 2001 GMC Safari van V6 4.3L. The van will RUN at normal temperature and blow warm air but when you come to a stop it blows cold air. What can you tell me about this problem. Changed thermostat and...


Try stopping on a steep incline--does the heater stay warm? If yes, what you have is an air bubble that hangs at the heater hose until pressure from the water pump blows thru it as the engine speeds up. Park on an incline, open the radiator cap, run the engine until the thermostat is open, and fill the radiator to the neck. Wait until the level stops dropping and make sure bubbles don't continue to come up. If they do, you may have a blown head gasket that will keep forming these bubbles until you change the gasket. Please let me know the outcome, as we are getting a lot of these cases and are trying to improve the answers.

Dec 14, 2010 | 2001 GMC Safari

3 Answers

We just bought a 1999 GMC Jimmy and the heater doesn't work. The fan blows but there is no heat. The air conditioner works fine.


Could be that the heater core is disconnected, there are two hoses that attach to the heather core that come out of the engine, this provides hot water to the core thus making the heater work, when the heater core starts leaking water the quick and fast fix would be to bypass the heater core and connect the two hoses together, check under the hood on the left passenger side there should be two hoses about 1" thick see if there are connected together or of they seem to be connected to 2 outlets that come out of the inside of the vehicle. people do that specially if selling vehicle.

Sep 06, 2010 | 1999 GMC Jimmy

1 Answer

I have a 2006 yukon, when I turn the heat to 90 I get heat, when I move it to 89 cool air starts coming out. My mechanic said that when it is on 90 it is going full bore and when I move it to 89 the air...


on the heater vent from the left side you will see a switch ture your heat on then watch the switch when you move the control to 89 see if it moves

Dec 24, 2009 | 1995 GMC Yukon

2 Answers

GMC Sonoma SLE 4.3L 1991- Coolant Temp Gauge Not reading


there are 2 coolant sensors one for gauge and one for ecm

Jul 23, 2009 | 1991 GMC Sonoma

1 Answer

I have a 89 bronco with efi that high edle when warm how do i fix this problem


Either your idle air control motor is sticking open OR you have a vacuum leak somewhere on the engine. First try removing the idle air control motor and cleaning it with aerosol carburetor cleaner. Reinstall it using a new gasket. See if that fixes it. It may fix it or the fix may only last a few days or a week. If the fix lasts a short time, you need a new control motor ($100) If a new idle control motor does not fix it, then you have to search for a vacuum leak (leaking rubber hose, leaking fuel pressure regulator, leaking power brake booster, etc) Charlie

Jun 14, 2009 | 1987 Ford Mustang

1 Answer

89 Honda Accord Heater doesn't blow air at all


sounds like the blower motor, Get a test light and hook it up to the wires going to the motor this will tell you if power is getting to the motor . Hopfully it is , Just pull the panel off on the pasangers side under the dash and you can see the motor . It's easy to change and should fix the problem. If you get no power it check for power at the switch on the dash . It could have gone bad !!

Feb 03, 2009 | 1989 Honda Accord 4 Door

1 Answer

94 gms safari van heater blower not working


This van has a resistor under hood for the blower motor and is the blower motor getting power to it

Jan 17, 2009 | 1989 GMC Safari

1 Answer

Heater does not work


Check blend door motor for proper operation (vacuum operated) if necessary, detach arm from heater box and move by hand. If you have heat then, change motor! You are reaching operating temp for engine, right? If not, thermostat is stuck open... Change.

Dec 22, 2008 | 1998 GMC Sonoma

Not finding what you are looking for?
Cars & Trucks Logo

556 people viewed this question

Ask a Question

Usually answered in minutes!

Top GMC Experts

yadayada
yadayada

Level 3 Expert

76070 Answers

Freddy

Level 3 Expert

1311 Answers

Colin Stickland
Colin Stickland

Level 3 Expert

22156 Answers

Are you a GMC Expert? Answer questions, earn points and help others

Answer questions

Manuals & User Guides

Loading...