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Old 06-09-2020, 01:07 PM   #1
AlphaCrow
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Blower motor doesn't work on high

2015 RAM 1500

Quick version: blower motor cuts out WHEN ON HIGH sometimes. I can get it back on by cycling the speed control from low to high a few times until it "catches" and starts working again. So anything less than high works all the time.

Why it's complicated: this is a new blower fan (with a new resistor as part of it). My previous motor was doing this but worse. When I started the truck with the fan on high, the motor wouldn't work at all. I'd have to restart the vehicle a few times to get it to spin. I assumed the motor, so replaced it all (including resistor). The new fan worked good for a bit, but will sometimes cut off on high. If I spin the dial back and forth between low and high, I can get the motor to cut on again on a low setting.

Multimeter to the plug shows voltage looks good and stable. I tried both with plug out and when plugged in to test the volts at the back of the plug.

I need to check behind the factory screen in the center of the dash to see if there are loose connections there perhaps, I did have some work done there a while back.

But with the problem persisting across 2 different motors+resistors, I have to think it is the plug, wiring, or computer? What sends the impulse to the blower fan?

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Old 06-09-2020, 03:34 PM   #2
brcidd
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Re: Blower motor doesn't work on high

Sounds like a bad connection at a plug- look for burnt/melted plastic at all connections- and yes you tested voltage, but that is only half the circuit- the ground connector and plugs are also trying to carry the massive current required of a high blower setting. This is why a relay is used- to avoid sending high current (amps) through your control head fan selector switch. You can tell which wires carry the high speed by their size. Big wires are for big current, all others are just for controls switching etc..
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Old 06-14-2020, 02:34 PM   #3
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Re: Blower motor doesn't work on high

Quote:
Originally Posted by brcidd View Post
Sounds like a bad connection at a plug- look for burnt/melted plastic at all connections- and yes you tested voltage, but that is only half the circuit- the ground connector and plugs are also trying to carry the massive current required of a high blower setting. This is why a relay is used- to avoid sending high current (amps) through your control head fan selector switch. You can tell which wires carry the high speed by their size. Big wires are for big current, all others are just for controls switching etc..
Happen to know where the other side of the plug goes to? The blower side plug seems fine, nothing burnt or melted.

Any chance it could be a loose connection on the back of the console screen? I had someone pull that out a while back (was considering if I could mod it) and that was around the same time as the problem starting. Before I waste time and probably break plastic screws holding the screen in, is there it worth looking back there?
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Old 08-31-2020, 03:19 PM   #4
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Re: Blower motor doesn't work on high

Hi again all!

I keep having this problem of this blower turning off at levels 5-7 randomly. I can get it to come back on by cycling down to 1 and back up to like 5 over and over until it goes.

This time I had a voltmeter attached to the plug (at the blower) waiting for this to randomly happen.

So the voltmeter never showed a loss of power. The volts on high were usually ~13.5. When the motor shut off the volts jumped to 14 v. When I got it to come back on, it dropped back to 13.5v.

So it's either the plug connection itself or I got a bad blower motor (even though it was new and the previous one did the same thing).

Thoughts?
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