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Discussion Starter · #1 · (Edited)
I have been noticing the last few days anyhow, that the heater speed changes at idle compared to driving. Try this: with the rear window defroster on, and the heater set to defrost and floor combo and the fan speed on #2. Notice the fan speed when the cars is at a idle then notice the fan speed when you start driving. Mine seems to slow down when driving. I hope i'm not nutz .... :eek:
 

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I have been noticing the last few day anyhow, that the heater speed changes at idle compared to driving. Try this: with the rear window defroster on, and the heater set to defrost and floor combo and the fan speed on #2. Notice the fan speed when the cars is at a idle then notice the fan speed when you start driving. Mine seems to slow down when driving. I hope i'm not nutz .... :eek:
I noticed that as well. It's like the BCM knows to reduce power to all the power hungry systems or at least divert more power to the more important systems until the car's charging system can bring the voltage up. Try it, heat warmers, defrosters, radio, and heater all on. And you'll see the heats basically don't heat up but the defrosters are still working normally and the fans are slower.
 

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Discussion Starter · #3 ·
Hmmm now i'm thinking about this and it's don't make any sense. Normally the voltage is down at a idle and things will slow down but mine is just the opposite, it speeds up at idle and slows down when i'm driving ..
 

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I wonder if upgrading to an aftermarket battery would help resolve this, i've notticed this as well but didnt worry too much about it as i had though it had to do with the above post.

I always shut off my radio, seats, etc before I shut off my car so when I start it, it's got full cranking amps, I do have the fog ligh drl mod and sometimes (rarely) one fog doesnt come on but I know I can fix this by adding a relay harness.
 

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Hmmm now i'm thinking about this and it's don't make any sense. Normally the voltage is down at a idle and things will slow down but mine is just the opposite, it speeds up at idle and slows down when i'm driving ..
I read your first post too quickly and got the opposite.
The opposite happens to me when I'm going the fan speeds up and idle it slows down.

All I can think of for your explanation is: When the car is driving flow-thru ventilation is taking place meaning air is just making it's way through the vents at the windshield in to the cabin and escaping out the back. Designers kept this in mind and designed the HVAC system so it compensates for this small boost in pressure by slowing the fan down to reduce power usage and save gas. And in the winter time there's snow blocking up the vents making this noticeable when it shouldn't be with clear vents. That's my best guess.
 

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I wonder if upgrading to an aftermarket battery would help resolve this, i've notticed this as well but didnt worry too much about it as i had though it had to do with the above post.

I always shut off my radio, seats, etc before I shut off my car so when I start it, it's got full cranking amps, I do have the fog ligh drl mod and sometimes (rarely) one fog doesnt come on but I know I can fix this by adding a relay harness.
You don't need to go through the trouble of shutting all those things off before you turn off the car. I've noticed that with the key in a position right before you crank it over it shuts off the main head lights, HVAC and radio.
I think most computer controller cars or at least cars with OBD do this. I've driven many cars over the years and they all shut everything down right before it cranks the starter.
 

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I posted on this way back in the summer, with the AC. When /not/ in recirc/max AC mode, once I hit 35 or so mph, the fan slowed down. Upon slowing down under 25mph, the fan sped back up. Happens the same in the winter too. Seems to be by design. It's not an issue with the alternator keeping up because voltage is lowest at idle
 

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Funny I havn't payed attention to the fan speed but just today I was wondering if there was something wrong with my car because it didn't seem to get warm in the cabin with the heat on full heat with the diverter on face and feet and the blower on 2, but it would make some sense if the fan slows down while driving it wouldn't blow as much hot air...


I dunno I guess I'll have to pay more attention, or roll up the window... haha J/K windows up...
 

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The air pressure outside the car when you're going faster makes up for the lower fan speed, especially at highway speeds.
 
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