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1998 GMC Sierra heater blower resister

Tiny
ADUBBER
  • MEMBER
  • 1998 GMC SIERRA
Heater problem
1998 GMC Sierra V8 Four Wheel Drive Automatic

Hello I am sending anouther request on my vehicle
I have only the high setting on the fan motor

I have replaced the air actuator the heater relay the
control pannel on dash and the heater blower resitor as requested by you guys,

up until I replaced the heater relay I couldnt controll the temp it was on high always.

what next? I am so frustrated with this now.
There are two wires going into the motor one is purple and the other is black test light works on the purple on high only tried it on lowest settring 1st
I see 2 yellow wires in a harness thas is connected to something on the fire wall but no others

after looking further I found the yellow wire going into the resistor and on low it has no power going to it
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Friday, January 15th, 2010 AT 6:02 PM

17 Replies

Tiny
RASMATAZ
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Hi adubber, Welcome to 2carpros and TY for the donation:

I want you to turn heater on set it at low and check for power at the yellow wire on the blower motor resistor let me know asap
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Saturday, November 17th, 2018 AT 9:41 AM
Tiny
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I testerd for power on the yellow wire with the fan on low and found no power
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Saturday, November 17th, 2018 AT 9:41 AM
Tiny
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Saturday, November 17th, 2018 AT 9:41 AM
Tiny
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Replace the blower switch
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Saturday, November 17th, 2018 AT 9:41 AM
Tiny
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What exactly are you refering to?
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Saturday, November 17th, 2018 AT 9:41 AM
Tiny
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The switch is within the HVAC control module


https://www.2carpros.com/forum/automotive_pictures/12900_b1_9.jpg




https://www.2carpros.com/forum/automotive_pictures/12900_b2_9.jpg

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Saturday, November 17th, 2018 AT 9:41 AM
Tiny
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Thats odd the new console had the switch attached
could the new switch be bad? Or could there be some other problem?

UPDATED 1-19-10
Hi,

I ran a power line from the battery terminal to the yellow wire going into the resistor and the blower run on low, I did the same with the brown and it runs the fan on med and on blue it runs on med high
the high comes on if you turn it to high before starting the vehicle
i9f you have it on any other setting and start the vehicle it don't but will turn on after a few seconds or minutes no pattern.
I tested the 25A heater fuse and its good I found a aircond- relay in the fuse box under the hood and replaced it but that didn't change
I noticed that the air cond- don't come on at first when you push the button and after a while the light on the panel turns on.
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Saturday, November 17th, 2018 AT 9:41 AM
Tiny
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Earlier you said you don't have power at the yellow wire on the resistor-if the switch is working properly the yellow wire should power up on the low position.
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Saturday, November 17th, 2018 AT 9:41 AM
Tiny
KHLOW2008
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Saturday, November 17th, 2018 AT 9:41 AM
Tiny
ADUBBER
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Hi,

I ran a power line from the battery terminal to the yellow wire going into the resistor and the blower run on low, I did the same with the brown and it runs the fan on med and on blue it runs on med high
the high comes on if you turn it to high before starting the vehicle
i9f you have it on any other setting and start the vehicle it don't but will turn on after a few seconds or minutes no pattern.
I tested the 25A heater fuse and its good I found a aircond- relay in the fuse box under the hood and replaced it but that didn't change
I noticed that the air cond- don't come on at first when you push the button and after a while the light on the panel turns on.

From: "forum@2carpros. Com"
Sent: Sun, January 17, 2010 1:56:14 AM
Subject: Topic Reply Notification - 1998 GMC Sierra heater blower resister
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Saturday, November 17th, 2018 AT 9:41 AM
Tiny
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[/quote:fda5d37c28]

Hi,

I ran a power line from the battery terminal to the yellow wire going into the resistor and the blower run on low, I did the same with the brown and it runs the fan on med and on blue it runs on med high
the high comes on if you turn it to high before starting the vehicle
i9f you have it on any other setting and start the vehicle it don't but will turn on after a few seconds or minutes no pattern.
I tested the 25A heater fuse and its good I found a aircond- relay in the fuse box under the hood and replaced it but that didn't change
I noticed that the air cond- don't come on at first when you push the button and after a while the light on the panel turns on.

From: "forum@2carpros.com"
Sent: Sun, January 17, 2010 1:56:14 AM
Subject: Topic Reply Notification - 1998 GMC Sierra heater blower resister

Hello,

You are receiving this email because there is a reply to your question, "1998 GMC Sierra heater blower resister" at Auto Repair Car Questions.

To view and follow-up on the reply to your question, please click on the following link, https://www.2carpros.com/forum/viewtopic.php?p=772779#772779

Sincerely,

Bob, Ken and all of the 2CarPros team.
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Saturday, November 17th, 2018 AT 9:41 AM
Tiny
ADUBBER
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[/quote:f708383860]

Hi,

I ran a power line from the battery terminal to the yellow wire going into the resistor and the blower run on low, I did the same with the brown and it runs the fan on med and on blue it runs on med high
the high comes on if you turn it to high before starting the vehicle
i9f you have it on any other setting and start the vehicle it don't but will turn on after a few seconds or minutes no pattern.
I tested the 25A heater fuse and its good I found a aircond- relay in the fuse box under the hood and replaced it but that didn't change
I noticed that the air cond- don't come on at first when you push the button and after a while the light on the panel turns on.

From: "forum@2carpros.com"
Sent: Sun, January 17, 2010 1:56:14 AM
Subject: Topic Reply Notification - 1998 GMC Sierra heater blower resister

Hello,

You are receiving this email because there is a reply to your question, "1998 GMC Sierra heater blower resister" at Auto Repair Car Questions.

To view and follow-up on the reply to your question, please click on the following link, https://www.2carpros.com/forum/viewtopic.php?p=772779#772779

Sincerely,

Bob, Ken and all of the 2CarPros team.
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Saturday, November 17th, 2018 AT 9:41 AM
Tiny
KHLOW2008
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Sorry for the delay in replying.

Just to be sure we are on the right track with the correct model, the circuit I have posted is for the 4.3 L engine. If it is not correct, please let me know.

From the last diagnosis, we are getting somewhere. You have a power supply fault and we are getting near to our destination.

The blower motor and resistor are perfectly good.

Power is not coming out of the HVAC control unit and you would need to test if power is available at the speed control switch. Test the brown wire for battery voltage with ignition switch turned ON.

If power is available and no voltage is available at the Yellow, Tan and Light Blue wire when speed is turned to low, M1 and M2 respectively, the control switch is faulty.
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Saturday, November 17th, 2018 AT 9:41 AM
Tiny
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Ok,
I will do that and let you know

You did mention the switch earlier and I went to baxter and purchased one and installed it
this didn't help the issue.
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Saturday, November 17th, 2018 AT 9:41 AM
Tiny
KHLOW2008
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You can test the switch for continuity according to the various speed mode.

Most important wire to test would be the power supply.

Was the switch replaced of the correct type?
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Saturday, November 17th, 2018 AT 9:41 AM
Tiny
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Yes I have also relaced the hvac control unit on the dash
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Saturday, November 17th, 2018 AT 9:41 AM
Tiny
RASMATAZ
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If you have power on the brown wire coming from the heater 25amp fuse when key is On and when you switch to low the yellow wire should have power-Is this happening if not were right back with HVAC control module. Now if yellow has power, blower motor should come On-if not-check and test the ground pointG201 at right side of dash. Get back with us
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Saturday, November 17th, 2018 AT 9:41 AM

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