No fan speed

Question 1

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Heater Blower not working on 1999 Chevy Tahoe.

Based on the detailed information you've provided, it seems that you've done a thorough job of testing the major components related to the blower motor system in your 1999 Chevy Tahoe.
Here are a few possibilities and additional steps to consider:

High Resistance in the Circuit: Even though the wiring and connectors appear to be in good condition, there might be high resistance somewhere in the circuit that only becomes significant under load. This could be due to a partially broken wire, a corroded connector, or a faulty switch. Carefully inspect the wiring harness for any signs of damage, wear, or heat exposure.

Issue with the Control Switch or HVAC Control Unit: The problem might be with the control switch or the HVAC control unit in the dashboard. These components can sometimes develop internal faults that are not immediately apparent. Consider testing the switch and control unit if possible.

Ground Connection Problem: A poor ground connection can cause voltage drop issues. Make sure the ground connections related to the blower motor circuit are clean, tight, and free of corrosion. This includes not just the ground for the blower motor, but any related grounds in the HVAC system.

Voltage Drop Test: Perform a voltage drop test on the blower motor circuit. This test is done by measuring the voltage across different parts of the circuit while the circuit is under load. A significant voltage drop across any specific part of the circuit would indicate where the resistance problem lies.

Check for Overloading or Short Circuits: There could be an issue elsewhere in the electrical system that's causing an overload or short circuit when the blower motor is connected. This might be difficult to diagnose without specialized equipment.

Jan 06, 2024 • Cars & Trucks

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Blower not working

Tell us what make an model of vehicle you are using in your description of the problem. Blower not working can be caused by:
1. Blown fuse
2. Bad fan switch
3. Bad resistor speed selector unit (changes voltage going to fan motor.
4. Melted or bad connector, usually between switch and motor.
5. You have lost the ground from the fan going back to the battery. ie, a bad connection.
You will need a volt/ohm meter after you check the fuse.
Make sure you have battery voltage (about 12 volts) coming to the fan switch. If you do get 12 volts, follow it in the circuit going to the blower fan until you stop getting 12 volts. Where it stops is where the problem is. You can also start the test right at the blower fan with a meter to see if the fan is getting 12 volts and work backwards towards the switch.
Most likely cause: Bad resistor pack or connectors melted going to it, followed by a bad fan switch.
Good luck!

Oct 02, 2018 • Cars & Trucks

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2answers

The fan for heating and cooling suddenly quit on my 2006 GMC Sierra 1500. Could it be a fuse?

Yes it could be a fuse, or the blower motor, or the control on the dash.

Feb 21, 2015 • GMC Sierra Cars & Trucks

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2answers

The heater fan only works on the 3rd fan setting, and only blows a little air. The A/C only works minimally when set on defrost and the 3rd fan speed setting. I was told I need a new control switch, but...

you need the service and repair manual in which you will find the part number and also how to fix the part with diagram you can get the manual from the given link http://toolsnyou.com/

Dec 11, 2017 • 2000 GMC Safari

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1answer

I have only low speed on the blower motor for heat The three wires connecting to the blower motor 1] red 12volts 2] think it a blk/yellow 2 volts 3] black ground i put 12 volts to wire 2 and the...

on the housing under the hood where your heater core and AC plumbing is there is a plug in rheostat that you need to remove and replace-take it off with the two screws that hold it and take it to a napa and they will sell you the replacement for about $20. Good Luck!

Oct 21, 2011 • 1994 Cadillac Seville

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1answer

Heater motor has stopped working. checked fuses snd they sre good what needs to be replaced

You need to check the blower motor to see if it has power going to it.Get volt meter hook the red end to the blower plug and put the black to a ground now turn the key and the fan on and see if you have 12 volts or more.If you do it most likly the blower motor

Dec 27, 2009 • 2004 Pontiac Grand Prix

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1answer

On my 1999 Buick LeSabre the blower fan does not work at all

How about checking voltage into & out of resistor for difference. Some swear by high only when resistor goes, but in past I have had intermittent use of other speeds before it finally went & I had high only.

Jun 06, 2009 • 1999 Buick LeSabre

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2answers

Tail light are not working

fuses under hood

POWER DISTRIBUTION BOX Location Name Amp Circuits Protected A Trailer Tow 50 Fuse 32/Fuse 26/Electric Brake B Fan (Hi) 60 Cooling Fan (CCRM) C Start 60 Starter Solenoid/Fuse 30/Fuse 36/Fuse 2 D Ignition 60 Fuse 6/Fuse 12/
Fuse 8/Fuse 18/Fuse 14/
Fuse 24/Fuse 20/Fuse 21/Fuse 27/Fuse 33 E Rear
Blower/
RAS 60 Rear Heater Blower Motor
Rear Air Suspension F Seat 60 Power Seats G — — Not Used H Fan-Lo 40 Engine Cooling Fans J Power Accessory 60 Fuse 13/Fuse 25/
Fuse 1/Fuse 31/Fuse 37/
Fuse 40/Fuse 7/Fuse 19 K Light 60 Headlamps/Fuse 10/
Fuse 11/Fuse 3/Fuse 9/
Fuse 23/Fuse 29/Fuse 35/Fuse 41/Fuse 17 L ABS 60 ABS Control/Pump Motor Module M Heated
Backlight 60 Heated Backlite/Fuse 16/Fuse 28/Fuse 22 N Fuel 20 PCM/Fuel Pump/CCRM P — — Not Used R PCM 15 PCM Memory S PCM 30 AX4S/Cylinder Identification Sensor/EDIS Module/PCM Power/EGR Control/HEGO's/IAC/
Injectors/MAFS/VMV T Alt./Reg. 15 Generator U Air Bag 10 Air Bag (Dedicated) V Trans. Light 10 Transmission Indicator Light W Fan 10 PCM Fan Monitor X Diode — Hood Lamp Diode Y Relay — RH Trailer Turn/Stop/Hazard Lamps Z Relay — Powertrain Control Module AA Relay — Windshield Wiper Speed BB Relay — LH Trailer Turn/Stop/Hazard Lamps CC Relay — Windshield Washer Pump Motor DD Relay — Windshield Wiper Dynamic Brake/Run
The fuses are color-coded by amp rating.

Fuse Value Amps Color Code 4 Pink 5 Tan 7.5 Brown 10 Red 15 Light Blue 20 Yellow 25 Natural 30 Light Green 40 Orange 50 Red 60 Blue

Mar 14, 2009 • 1997 Ford Windstar

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2answers

1999 cadillac deville blower dont operate. What should the voltage be at the red wire and the gray wire or the black wire ? Iam assuming the red wire should be 12 volts, the gray wire should be variable...

red black and gray are just half the connections. Red is positive 12 volts coming from fuse of circuit breaker. The black wire is either the ground or the main hot wire going to the blower motor (3 pin connection only), and the gray wire (if is is small in size) is a variable voltage coming from the body control module requesting speed for the blower motor.The blower control module varies voltage on the main wire going to the blower motor, supposedly in accordance with the requested voltage from the body control module. Usually if all fuses are okay and present on the apprpriate wire of the blower control module, the a blower motor that will not run or stays running after the key is turned off is the fault of the blower control module. If the blower control module has failed the the cause must be determined (over amping blower motor) or else new blower control module may fail when powered up.Usually blower control modules have more than three wires. Usual connections are: B+ (battery voltage) GND (chassis or engine ground), two large wires going directly to blower motor (can be any color, but are usually 10 guage in size), and an optional wire that reports voltage level back to the body control module.

Jan 11, 2009 • 1999 Cadillac DeVille

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1answer

Relay/resistor heater blower

There are two fuses for the fan. One is probably a 20 Amp in the fuse panel in the cab and marked "Heater". or "Heater/AC" The second is under the hood may be marked Heater, Blower, or Fan and should be 30 Amp. The one in the cab supplies switched 12 volts to the fan speed switch. The one under the hood supplies the 12 volts to the relay. The relay is normally energized by the 12 volts through the 20 Amp fuse in the cab and through the switch. I think you find that the fan has the normal speeds except for missing HI with the underhood fuse removed, and will turn off with the ignition that way. There is no hazard in operating it that way but you may want to replace the resistor/relay assembly before it gets too cold. The relay is a pretty trouble free device in most cases, maybe you can find a deal on a good one at a junkyard.

The whole idea with the relay under the hood started back in the Sixties believe it or not. There is considerable voltage drop in the wiring between the fan switch and the blower fan motor. By adding the relay under the hood right next to the motor, the voltage drop was reduced, both by the shorter wire, and by using heavier wire to boot. The motor gets really close to the full system voltage when the relay is closed. In your case where the relay keeps the fan running, it can drain a battery rather quickly too!

Dec 18, 2008 • 2004 Chevrolet Silverado 1500 Crew Cab

Question 2

Frank Magliocca

Cars & Trucks Master 1,461 Answers
Posted on May 16, 2019

Frank Magliocca

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Could be the switch

Answer 2 · 3/3/2009 12:00:00 AM

Anonymous

4669 Answers
Posted on Mar 03, 2009

SOURCE: Heater/AC blower will not operate

Replace the blower resistor.

Anonymous

1 Answer
Posted on Apr 24, 2009

SOURCE: 2002 Sebring LXi Convertible Starter Motor Fuse Blown 2x

Starter solenoid. I don't have the page here but in chiltons a page shows the ignition to fuse to relay to starter and if you look closely it's quite basic. I had same problem with constant fuse blow #8. The solenoid over time wears and sometimes sticks. When it sticks, your system can overload thus burn fuse. I bet you never stalled out while driving, but only when you shut off and start somewhere it's a no go. That's because you're system is already engaged. I had to change starter as solenoid part of it all. I see others suffer this same problem so please share this around. Solenoid can stick for a millisecond.

Anonymous

1118 Answers
Posted on Oct 11, 2009

SOURCE: 1997 Chevy s-10 pickup (2.2L) Blower Motor problem

I don't know what you mean by temp module but i'am gessing the switch on the dash, but to me it sounds like the resister is bad, i believe its located under the hood on the air box if not than chk. under the dash by the heater motor, i have seen the wires burn that plug into it when they go bad, thats what makes the blower run and also regulates the speeds of the blower motor.

Anonymous

108 Answers
Posted on Jan 31, 2010

SOURCE: 2005 Crown Vic climat contr fan not working Fuses good Motor good

does it have a digital control panel? As this uses an electronic blower speed controller located at the engine compartment (rear engine block) fix on ac phlenum try to shake the connector or wire while the system is on.

swampthang90

18 Answers
Posted on Mar 07, 2010

SOURCE: 2006 Hummer H3 a/c & heater fan/blower failed

Probably too late now, I am sure you have already fixed it, but mine did this and it was an electrical part that is mounted right beside the blower fan. The part was OK, but the plug into the part was arcing and burned out the connection. A Chevy mechanic told me this has been happening to MANY Chevy products. I had to buy a new part and plug assembly with new wires, about 100 dollars, and I spliced them together. It was an Easy fix, but I shouldn't have had to do it :(

Answer 3 · 3/3/2009 12:00:00 AM

Anonymous

4669 Answers
Posted on Mar 03, 2009

SOURCE: Heater/AC blower will not operate

Replace the blower resistor.

Answer 4 · 4/24/2009 12:00:00 AM

Anonymous

1 Answer
Posted on Apr 24, 2009

SOURCE: 2002 Sebring LXi Convertible Starter Motor Fuse Blown 2x

Starter solenoid. I don't have the page here but in chiltons a page shows the ignition to fuse to relay to starter and if you look closely it's quite basic. I had same problem with constant fuse blow #8. The solenoid over time wears and sometimes sticks. When it sticks, your system can overload thus burn fuse. I bet you never stalled out while driving, but only when you shut off and start somewhere it's a no go. That's because you're system is already engaged. I had to change starter as solenoid part of it all. I see others suffer this same problem so please share this around. Solenoid can stick for a millisecond.

Answer 5 · 10/11/2009 12:00:00 AM

Anonymous

1118 Answers
Posted on Oct 11, 2009

SOURCE: 1997 Chevy s-10 pickup (2.2L) Blower Motor problem

I don't know what you mean by temp module but i'am gessing the switch on the dash, but to me it sounds like the resister is bad, i believe its located under the hood on the air box if not than chk. under the dash by the heater motor, i have seen the wires burn that plug into it when they go bad, thats what makes the blower run and also regulates the speeds of the blower motor.

Answer 6 · 1/31/2010 12:00:00 AM

Anonymous

108 Answers
Posted on Jan 31, 2010

SOURCE: 2005 Crown Vic climat contr fan not working Fuses good Motor good

does it have a digital control panel? As this uses an electronic blower speed controller located at the engine compartment (rear engine block) fix on ac phlenum try to shake the connector or wire while the system is on.

Answer 7 · 3/7/2010 12:00:00 AM

swampthang90

18 Answers
Posted on Mar 07, 2010

SOURCE: 2006 Hummer H3 a/c & heater fan/blower failed

Probably too late now, I am sure you have already fixed it, but mine did this and it was an electrical part that is mounted right beside the blower fan. The part was OK, but the plug into the part was arcing and burned out the connection. A Chevy mechanic told me this has been happening to MANY Chevy products. I had to buy a new part and plug assembly with new wires, about 100 dollars, and I spliced them together. It was an Easy fix, but I shouldn't have had to do it :(

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No fan speed

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Frank Magliocca

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No fan speed

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Heater Blower not working on 1999 Chevy Tahoe.

Blower not working

The fan for heating and cooling suddenly quit on my 2006 GMC Sierra 1500. Could it be a fuse?

The heater fan only works on the 3rd fan setting, and only blows a little air. The A/C only works minimally when set on defrost and the 3rd fan speed setting. I was told I need a new control switch, but...

I have only low speed on the blower motor for heat The three wires connecting to the blower motor 1] red 12volts 2] think it a blk/yellow 2 volts 3] black ground i put 12 volts to wire 2 and the...

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Relay/resistor heater blower

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