Join the Car Talk Community!

Discussion Rules

Welcome to the Car Talk Community!

Want to ask a question or join the discussion? Great! Join now.

Sign In Register

Heater only works on highest setting

2004 Chrysler Sebring. The heater will only turn on when I put it at the highest setting (#4). It is completely silent at 0-3. The air is nice and hot when it does come out, but I get no response until I turn it all the way to high. I switched it to air conditioning and it's the same problem, so I'm assuming it's in the blower, but I really don't have any clue from here. Any ideas?
Tagged:
«13

Comments

  • edited January 2011
    It's the blower motor resistor.
    12 volts direct to the motor is high speed. The resistor gives you the slower speeds and has a thermal breaker that is blown now.
  • edited January 2011
    It's not the blower. It is the blower motor resistor pack that is designed to cut the voltage to the blower motor to control the fan speed. The resistor pack is by-passed on setting #4, so the blower motor gets a full 12V, running as fast as it can. Typically, these are located in the duct path close to the blower fan. The air running from the blower cools the resistors when running. Some of these packs are cheap, and some are expensive. They should have a 5-wire or 6-wire connector on it.
  • edited January 2011
    I've changed oil, and done a disc brake job. Is this something I can do on my own?
  • edited January 2011
    Sure. Check the vehicle repair guides at www.autozone.com for directions. You may need to go to the dealer for the resistor pack. I did for my Toyota.
  • edited January 2011
    I got a replacement resistor pack for a Buick at Advance Auto Parts. Check you local parts store stock on line to see if they have one, or call around. If the Chrysler location is anything like the Buick's, the resistor pack will be under the glove box; behind the blower motor. It's a little difficult to get to, but you can certainly do it. Follow the wires leaving the blower motor back to the resistor pack.
  • edited January 2011
    I agree it most likely is the blower motor resistor but the technique is described wrong. The way the speed is varied is the by adding resistance on the ground side of the circuit. For full speed only minimal resistance to ground, for slowest speed the most resistance to ground. I do find it odd from a group that always pops up with "check the ground" that you guys got this technique wrong.
  • edited January 2011
    What, pray tell, was wrong with the statements by me and ken? If it is on the 12V feed or the ground side, the resistor pack still cuts the speed by controlling the voltage through the blower motor by adding resistance to the circuit. Basic electrical 101.
  • edited January 2011
    BK I can understand the confusion. It is that 12v is always there but the resistance to ground is what is responsible for fan speed. Sounds backwards I know but that is how I understand some of the systems.
  • edited January 2011
    Some use seperate circuits for the low and high. On low it runs through a resistor which may be fused. If you only have high, the low circuit or resistor is not getting current. Check fuses. Check continuity in resistor. Some have a thermal protection internally that quits. If resistor is bad motor may be going causing high current. Check amperage draw at motor on high. Typically 50% of fuse rating. A slow motor raises current.If motor is binding more current has been going through low circuit. Make sense?
  • edited January 2011
    It's not resistance to ground it is total circuit resistance that is important. It's Ohms law. Take 1 V to push 1 amp through 1 Ohmm. The absense of power = ground and visa versa. Doesn't matter where the resistance is. My chevy has resistor on "hot" leg. What if motor is component ground?
This discussion has been closed.