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Fan motor only blows on high


bigkylewhite
01-26-2008, 07:46 PM
'97 Suburban diesel. Heater fan only works on high. I replaced what looks like a relay (black square about 1" in each dimension) mounted behind the glove box on the left side of the top of the heater housing with about 5 wires plugged into it. That didn't fix it. I've read about a resistor pack. Did I replace the resistor or the relay and if I replaced the relay, can someone tell me where the resistor is located and what it looks like?

777stickman
01-27-2008, 11:08 AM
'97 Suburban diesel. Heater fan only works on high. I replaced what looks like a relay (black square about 1" in each dimension) mounted behind the glove box on the left side of the top of the heater housing with about 5 wires plugged into it. That didn't fix it. I've read about a resistor pack. Did I replace the resistor or the relay and if I replaced the relay, can someone tell me where the resistor is located and what it looks like?

If what you replaced actually had 5 wires to it then it was the relay. The resistor pack is in the same area and has four wires to it. The wire colors are yellow, tan. light blue and dark blue.

1. Yellow is low feed to the resistor from the fan switch.
2. Tan is Med 1 from the fan switch.
3. Light blue is Med 2 from the fan switch.
4. Dark blue is feed from the resistor pack thru the relaxed contacts of the relay to the motor.

Before you replace the resistor pack check for power coming from the fan switch to the resistor pack on wires 1 thru 3 with the key in the run position and the fan speed switch selected to match the wire colors.

j cAT
01-27-2008, 11:19 AM
'97 Suburban diesel. Heater fan only works on high. I replaced what looks like a relay (black square about 1" in each dimension) mounted behind the glove box on the left side of the top of the heater housing with about 5 wires plugged into it. That didn't fix it. I've read about a resistor pack. Did I replace the resistor or the relay and if I replaced the relay, can someone tell me where the resistor is located and what it looks like?

there is no need to check for voltages or fuses or relays as you stated fan operation on hi only. this means resistors are open as these only are used to slow down fan........... when you remove the resistors it will be apparent that this is bad because of the coatings falling off and damage is visable this is about 40.00 i believe....

bigkylewhite
01-27-2008, 09:17 PM
Thanks for the help guys. NAPA had a resistor on the shelf for $20. Swapped it out this afternoon and now it works for the first time since I bought the Sub 4 months ago.

j cAT
01-28-2008, 12:15 PM
Thanks for the help guys. NAPA had a resistor on the shelf for $20. Swapped it out this afternoon and now it works for the first time since I bought the Sub 4 months ago.


make sure air inlet and if it applys cabin air filter is kept clean/clear of debris as this will shorten life of these fragile resistors............

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