# 2018 Sentra blower loses power



## Lana (Dec 16, 2020)

I’m not even sure I’m posting in the right place... the blower in my 2018 Sentra will just gradually lose power until it quits. No noises that I can hear, no rattles or anything, just fades away. If I mess with the fan speed switches it’ll sometimes come back, other times I have to turn the heat off completely, wait a bit, then turn it back on. Suggestions? Of COURSE, I put on a lot of miles so it’s past the 60,000 warranty.


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## rogoman (Dec 16, 2004)

Lana said:


> I’m not even sure I’m posting in the right place... the blower in my 2018 Sentra will just gradually lose power until it quits. No noises that I can hear, no rattles or anything, just fades away. If I mess with the fan speed switches it’ll sometimes come back, other times I have to turn the heat off completely, wait a bit, then turn it back on. Suggestions? Of COURSE, I put on a lot of miles so it’s past the 60,000 warranty.


There's something called a variable blower control (blower motor resistor) that may be bad. It's located on the left side of the A/C- heater box. To get to it you'll have to remove the instrument lower panel LH.


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## Lana (Dec 16, 2020)

There's something called a variable blower control (blower motor resistor) that may be bad. It's located on the left side of the A/C- heater box. To get to it you'll have to remove the instrument lower 

I managed (finally) to get the cover off to check the cabin air filter and it’s TOTALLY plugged. So I’m thinking the air restriction was maybe causing the blower to overheat and start losing power. Now to get a new one in....


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## VStar650CL (Nov 12, 2020)

Was the blower still running fast (audibly) but with no air movement? If so, then the plugged filter was likely causing it. The plug will cause the blower cage to run in a partial vacuum, so it won't overheat, but it will run faster than normal without moving much air. The effect is akin to plugging the wand of a vacuum cleaner with your palm, you can hear the motor suddenly race because the impeller is running in a vacuum and has no air resistance to work against. If your blower was running audibly slower, then a failing VBC is the likely culprit. They call them "blower resistors", but the one in your Sentra is actually a high-powered MOSFET transistor that's fed a variable gate voltage (PWM) to make it act like a variable resistance. When they're on the verge of failing "open circuit", they often carry less current as they heat up, causing a drop in blower speed. If the VBC is failing, it's wise to replace the blower as well unless you find something obvious in the cavity that's jamming the cage. Nissan VBC's are pretty rugged (60 amps), so they don't usually blow without a reason. Usually the reason is a worn-out blower with bad brushes that are causing it to draw excessive current on startup. The high current is what kills the FET, but there's no good way to check startup surge without an oscilloscope. So the general rule is that a VBC can be left in place if the motor is bad but the VBC is good, but if the VBC is bad and the motor _appears_ good, replace the motor anyway.


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