Chevy Suburban
Heater Cores and Blower Fans
Jeep Grand Cherokee Laredo

Why would the heater on a 1997 Chevy Suburban work at all speeds except high and the back blower not come on at all?


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2006-06-26 05:52:45
2006-06-26 05:52:45

The two blowers share two things in common that are worth checking, the fuse (#12 on the interior panel) and therefore powersource, and the Hi-blower relay (3rd from the bottom-right of the under-hood relay/fuse block). Before continuing, however, it would be helpful to know the exact combinations of working/not-working for your problem. For instance, Front blower working off: Back blower Low - works Med - works High - works Front blower on low: Back blower Low - works Med - works Hight - fails Also, with/without the A/C on MAX, and the A/C on/off at all. You get the idea. Now back to my original comments... If you can test the scenario(s) at night when you have darkness and can examine subtle lighting changes, like the dome lights that would be good. Assuming that you don't have significant lighting changes when moving the switch(es) to different settings, you probably don't have a "short" problem. Note: a short may not always lead to a fuse blowing, but may have led to a burned switch and/or wire, motor, etc. It really sounds like you have two different problems. The "Hi" setting on the working blower and a fail-to-run problem on the other. The first thing to do would be to double check the relay I mentioned above in the under-hood panel. Once that's done, try the following steps to isolate the issue. Do: Remove the power lead to the rear blower and try the front blower in all positions. Then: If it works fine you know it can on it's own. Do: Plug the rear blower back in, and retry the front blower. Then: If it doesn't work, you probably have a rear motor burning the relay. Check it again. Also: If it works, you've shown the rear motor doesn't have an effect in the off position. Try turning the rear motor to different speeds and see if the front motor fails (while at high) in any power-on settings for the rear motor. Also: If not, you've shown the two to likely (99%) unrelated. For the rear motor... Do: Disconnect the motor and use leads to run the motor straight from the battery. NOTE: You should connect the leads to the battery and the motor with different leads, so that your final connection is with alligator clips or such. The final connection that powers the motor has the potential to burn the connection point. You don't want it to be the terminals or vehicle connections. Also, make a solid connection with waivering, then a solid release if it turns or does not turn. It will only take a second to check it. FUSE THE LEAD YOU USE!!!! use a lead that has an inline fuse with amperage to match the factory fuse in the fuse-block!! Then: If the motor turns, you will have to chase a connectivity issue (known as an open) throughout the system. Also: This will be best accomplished with the power off and an ohmmeter between the fuse block and all the locations you can imagine. Start with the front-upper-console, then the rear-upper console, then perhaps the lead at the motor. While checking the connections, move the switches to various postions to ensure you have some/none success in an "willing" position. The one place you should have success with the continuity check is the front-upper-console, in one of the various power positions. GOOD LUCK!! I'll check back. User - Atis


Related Questions

Heater blower resistor is what controls the low medium high speeds...

It gives you all the blower speeds except high.

A bad heater blower motor resistor would effect one or more blower speeds other than high.

With no speeds at all, check the fuse, then check the blower speed switch and it's electrical plug.

blower resistor especially if its chrysler/jeep or blower switch

Blower wont work on all 5 speeds, usually the lower speeds tend to go first.

most vehicles have one circuit(and one fuse) for the first 3 fan speeds and a separate circuit and fuse for the highest speed.AnswerCHECK THE BLOWER MOTOR RESISTOR

The blower motor resistor is defective. They go bad when the blower motor pulls to much amperage.

You have a relay located behind the glove box once removed to the left and you also have a blower resister that controls the speeds located on the passengers side in the blower motor housing..............

replace the resistor pack on the fanblower, under glowecompartment

Only for the high speed blower function. The lower speeds go thru the blower motor speed resister.

It sounds like the blower resistor assembly is defective. All fan speeds except for high go through resistors (that is what controls the speeds from low to high). Number 4 is high and has the full 12 volts going to the fan.

Could be hi-speed fan relay or secondary winding in blower motor

Yes, located in the blower motor resistor pack. Follow the wires backward from the blower motor to find it.

If it has only high speed, the blower motor resistor has to be replaced to get all speeds back.

If all speeds do not work, suspect the fuse, the switch, the switch connector or the blower motor. If only high speed works, suspect the blower motor speed resistor. If low speeds work and not high, suspect the blower motor relay.

Sounds like you need to replace your blower motor resistor.

could be thermostat or heater fan if you can hear all the speeds on the blower motor working then it could be your thermostat but your heater core might be plugged as well

These and similar vehicles use a "hi-blow" relay to put the blower motor into high speed. The low speeds are controlled by putting various taps from a limiting resistor into the motor cicuit. The hi-blow relay is not going to be at fault since the motor runs fast. It's possible you have an electronic temperature control that has a defect. Most likely, though, is the resistor is burned out or disconnected. The resistor is usually in the heater blower box so the moving air can keep it cool.

If the heater fan works on all speeds, then the blower motor, blower fuse, blower relay, and blower motor resistor pack are all good. If the fan runs but nothing comes out of the vents, you have a 'mode door' issue (which might include a bad control head).

More than likely the blower motor resistor pack is bad, although it can also be the switch itself.

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