1997 HVAC fan only works on highest setting

JoeyJeeper94

JoeyJeeper94

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Oct 12, 2017
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Happy Valley, OR, United States
Howdy All,

So a little background, i have a 97 2.5L with the sliding heater controls and the electrical turn knob for fan speed. No AC. The heater pumps out the heat really well but only on the highest setting and through all of the vent settings. If i turn it to the third setting you can feel a very slight amount of heat coming out while driving at highway speeds. I replaced the blower motor resistor located under the passenger side dash with no effect. Pulled the whole control unit off the dash and used grit cloth to clean all the connections on the actual switch and didn't change anything.

Any other suggestions?
 
JoeyJeeper94 said:
Howdy All,

So a little background, i have a 97 2.5L with the sliding heater controls and the electrical turn knob for fan speed. No AC. The heater pumps out the heat really well but only on the highest setting and through all of the vent settings. If i turn it to the third setting you can feel a very slight amount of heat coming out while driving at highway speeds. I replaced the blower motor resistor located under the passenger side dash with no effect. Pulled the whole control unit off the dash and used grit cloth to clean all the connections on the actual switch and didn't change anything.

Any other suggestions?
Click to expand...

That really sounds like a bad blower motor resistor, you said you already replaced it? Could the replacement be bad? ( wouldn’t be the first time I have seen that lol) as for a little heat coming out on highway speeds on the 3rd setting, I have had many cars that put out heat with everything off when you started going faster than 20-30 miles an hour.. so idk if that is anything more than that..


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Jerry Bransford said:
How was the wiring leading to the resistor pack? That wiring is known to melt and cause problems, it happened to my '97 TJ.
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I have heard about this too, i actually replaced my resistor today haha and was hoping I didn’t run into that. But yea they get super hot and can melt when they malfunction.


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Rubirob said:
That really sounds like a bad blower motor resistor, you said you already replaced it? Could the replacement be bad? ( wouldn’t be the first time I have seen that lol) as for a little heat coming out on highway speeds on the 3rd setting, I have had many cars that put out heat with everything off when you started going faster than 20-30 miles an hour.. so idk if that is anything more than that..


I guess the next step would be to try a new resistor. Considering I bought it at good ol autozone, it could definitely be a faulty one.

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Click to expand...
 
My suggestion is to get out a test light, take the control panel off, and start at the highest setting with the blower. You should get the test light to light up, showing that it's sending power to the blower motor.

Then turn it to the 3rd highest setting and see if the test light comes on, then 2nd, and then 1st. If you're not getting a lit up test light on some of the settings, but get it on others, that seems to suggest that your control unit itself is bad (which I've heard of happening before). This is a cheap and easy way to rule out the controls themselves IMHO.
 
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Chris said:
My suggestion is to get out a test light, take the control panel off, and start at the highest setting with the blower. You should get the test light to light up, showing that it's sending power to the blower motor.

Then turn it to the 3rd highest setting and see if the test light comes on, then 2nd, and then 1st. If you're not getting a lit up test light on some of the settings, but get it on others, that seems to suggest that your control unit itself is bad (which I've heard of happening before). This is a cheap and easy way to rule out the controls themselves IMHO.
Click to expand...

Testing stuff is always the best way to figure out problems! As long as you know what too test haha which I don’t always know [emoji854]


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Chris said:
My suggestion is to get out a test light, take the control panel off, and start at the highest setting with the blower. You should get the test light to light up, showing that it's sending power to the blower motor.

Then turn it to the 3rd highest setting and see if the test light comes on, then 2nd, and then 1st. If you're not getting a lit up test light on some of the settings, but get it on others, that seems to suggest that your control unit itself is bad (which I've heard of happening before). This is a cheap and easy way to rule out the controls themselves IMHO.
Click to expand...

Would I attach the test light between the control and wiring then you’re saying? To see if I’m getting power to the wire and not the switch maybe?
 
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JoeyJeeper94 said:
Would I attach the test light between the control and wiring then you’re saying? To see if I’m getting power to the wire and not the switch maybe?
Click to expand...

That's what I was thinking. I haven't had my control unit off my dash, so I'm not sure what it looks like, but I assume there's multiple wires back there. Figure out which one doesn't have power when the blower is off, but once you turn it on, gets power (the test light will light up). It should have power on every setting. If not, it could be the switch.
 
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So today I went and bought a new blower motor resistor today (number 2) and still no change so I think it’s safe to say I’m not using a faulty part. While I had the resistor off, I put my test light on the positive side and touched each of the 4 prongs on the wire connector that would normally connect to the resistor and It would only light up on one of the prongs indicating that I was getting power to one prong. Could this mean the issue is before the resistor even or should I try a new switch next? I have to order one before I can try the switch
 
JoeyJeeper94 said:
So today I went and bought a new blower motor resistor today (number 2) and still no change so I think it’s safe to say I’m not using a faulty part. While I had the resistor off, I put my test light on the positive side and touched each of the 4 prongs on the wire connector that would normally connect to the resistor and It would only light up on one of the prongs indicating that I was getting power to one prong. Could this mean the issue is before the resistor even or should I try a new switch next? I have to order one before I can try the switch
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I would take that as the issue being before the resistor, maybe Chris has an idea but I’m at a loss.. I hate the idea of buying the switch and installing it and that not being the problem either. I could be wrong but did you cycle thru the settings while checking them? Without a resistor it might blow on full for everyone but I would imagine it would try to use the blades needed for each setting, marking the bulb light up.. idk I am just guessing so take it with a grain of salt haha


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After reading many pages of the FSM thanks for that by the way Chris that’s an awesome resource, I could also try the blower motor relay it sounds like. My only question with that is does anybody know if the blower motor relay is faulty, wouldn’t ALL of the blower motor speeds not be functioning?
 
Well today I solved my problem. FINALLY!

I went to the store and got a blower motor switch after work, drove home and installed it. No difference. At this point I was ready to set fire to the jeep so I took another look at the FSM and under the heater/AC section found the location of the blower motor relay which was right behind the glove box sitting upright. I’ll try to attach a picture. Another trip down to the store to pick up a new relay and to return the blower motor switch and I have heat on all four settings! Thank you all for the input and help.

So in short if you only have air movement on the highest setting on your jeep try these three things in this order:

1) blower motor relay located behind the glove box standing upright (around $15)
2) blower motor resistor located under the passenger side kick panel (around $25-$30)
3) blower motor switch (around $30)

Keep on Jeepin’ on, now I just need to figure out my coolant leak...

01A597FF-B6E0-4EB3-971D-3E55737FF01F.jpeg
 
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JoeyJeeper94 said:
Well today I solved my problem. FINALLY!

I went to the store and got a blower motor switch after work, drove home and installed it. No difference. At this point I was ready to set fire to the jeep so I took another look at the FSM and under the heater/AC section found the location of the blower motor relay which was right behind the glove box sitting upright. I’ll try to attach a picture. Another trip down to the store to pick up a new relay and to return the blower motor switch and I have heat on all four settings! Thank you all for the input and help.

So in short if you only have air movement on the highest setting on your jeep try these three things in this order:

1) blower motor relay located behind the glove box standing upright (around $15)
2) blower motor resistor located under the passenger side kick panel (around $25-$30)
3) blower motor switch (around $30)

Keep on Jeepin’ on, now I just need to figure out my coolant leak...
Click to expand...

Thanks for the follow up, this is good information for anyone with blower motor problems.. seems kinda common in the TJs haha. I fixed mine with the resistor.. but if that didn’t work I would have been lost haha


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Rubirob said:
Thanks for the follow up, this is good information for anyone with blower motor problems.. seems kinda common in the TJs haha. I fixed mine with the resistor.. but if that didn’t work I would have been lost haha


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Yeah hopefully this will save somebody else from a headache like mine. The list of those three is just cheapest and easiest first. Maybe not the most common first. I know you can also do a continuity test on the relay before buying one.
 
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