Heat / AC only come on when blower is set to highest setting (4)
My 99 Honda has a blower setting from 1 (lowest) to 4 (highest) for the heat and AC.
For the last few weeks, it has not come on in position 1, but worked for 2,3, and 4. This week, it will only come on when switched to the highest blower settting (4). What could be wrong, and is it a simple fix?
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Re: Heat / AC only come on when blower is set to highest...
Not exactly sure if it's an easy fix without looking at it , but is seem to be the switch is going out, usually have to take dash trim off to expose the bolts to get the switch housing out. Then the switch will come off from the back side , and you'll have to unplug the wireing plug from it, to replace it.
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I would need some more clarification to get you a 100% answer but based on some assumptions I can give you 2 possible solutions.
It is possible your blower isn't working. You going down the high way is getting enough air through the venilation to bring heat into your car. If this is the cas while you are parked turn your blower setting down to the lowest point. Listen then turn it up to the highest setting and listen again. If you don't hear a fan running on the highest setting you need to replace the blower.
The other possibility off the top of my head is a bad thermostat. Your car isn't getting hot enough to trip it until your on the highway. If this is the case simply replace the thermostat.
Sounds like your blower motor relay. Look on your unit housing (under the hood), there should be a plug, disconnect it, find your power lead and use a jumper to different posts. You'll know as your fan speed will change. Hope this helps
The switch that runs the blower motor for air and heat sends the DC voltage through some big resisters when it isn't set on high. (On high it sends all the power to the motor.) If the lowest speed doesn't work then one of the resisters has gone bad, or come disconnected. If more than 1 speed doesn't work then a differant resister has gone bad or disconnected. The power runs through each resister in series so the most common one to go bad is the second to highest speed. when this resister is bad thaen it will only work on the highest setting. Replacing the switch won't fix it. You will have to find the resister that is bad and replace it. The resister bank is usually tucked up behind the dash where only a kid can focus his eyes, and contort himself enough to see it. Once the resister is replaced it should run perfectly. Presto.
Usually when the blower fan only operates on hi speed, its because of a failed blower motor resistor. You still have hi speed because on hi, the power going to the blower motor goes directly to it, as opposed to the lower speeds, when the power is routed through the resistor, thus lowering the voltage, which in turn lowers the speed of the fan. The resistor is usually located near the blower motor itself, under the hood back near the firewall.