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?

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.

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.

I’ve changed oil, and done a disc brake job. Is this something I can do on my own?

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.

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.

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.

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.

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.

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?

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?

What is wrong is that people should be aware of the technique used. Adding resistance to the ground leg is a very common technique that should not be confused with varing the supply side.

A 2003 Chevrolet Impala uses the same technique as the Sebring in this thread. the variying the ground is widely used with GM and has been for 25+ years, why not explain the circuit like it really is?

When people know how the circuit works it is easy to explain why they only have high speed, the reason is all other paths to ground are gone except the direct one on the high speed circuit.

It was in essence a location of the resistance that caused the question. IE you reduce the voltage before the motor via voltage input you reduce the motor speed. if you reduce the ground connection after the motor you reduce the speed.

we are on the same page, OS.

All I’m gonna say is you probably oughta check out a wiring diagram on a 03 Impala.

Check out a ford. http://circuitzoo.com/wp-content/uploads/2010/04/heater-air-conditioner-circuit-diagram_thumb.png

Blower motor resistor is pretty simple…once you locate it. I changed one on my wife’s RAV4 last winter, took about 3 minutes(only because of the cold temps). Your auto parts person should be able to show you a diagram regarding the location of the resistor.

I did ,so what is your point?

Point is 03 impala varies resistance on power side, not ground as you stated above. Facts are facts.

Not from my viewing of the schematic is it shown to be like this. Yes I see the switch is supplied with a constant source and the voltage is dropped before the motor.

Still the technique of varying the ground is used with many other GM vehicles (mainly (Suburbans and pickups from the 90’s)

The Sebring does use the after the motor technique, the Impala was a wrong example to use.