Hello all,
Working on the blower motor in my 93 400E, and I'd like to run my thoughts past you guys to see if my diagnosis is on the right track.
High fan speed does not work when selected on the PBU, nor does the fan go to high when defrost is selected. It only runs in low, so very little air is moving through the vents. Wiggling the ignition switch and slightly turning it back towards off doesn't change anything, plus the I did replace it a few years ago as well.
Fuse F15 on the drivers side shock tower is confirmed good, so I pulled the blower fan and regulator out to test them, but left them connected to the car so I could test the circuits at the regulator. I attached the blower motor to a block of wood and set it on the engine so I could test everything under load, and get to the regulator with the fan running. On the yellow wire at the regulator I"ve got 9.13 volts on high, 4.41 volts on Auto, 1.5 volts on low, and 3.3 volts when in defrost. I took the connector above the brake booster apart and removed just the yellow wire pin to test the motor. Jumped across the blue and black wires at the regulator, and the fan runs in high like it should, moves lots of air. Voltage drop from black wire on regulator to ground is .2 volts and red wire on regulator to F15 fuse is .3 volts. Red wire on regulator to B+ at distribution lug behind the ECU in the cowl is .8 volts. That says to me that the fan itself and the circuit supplying it are good.
Just for grins, I took a variable resistor and supplied the yellow wire to the regulator (de-pinned from the connector above the brake booster) with varying voltage up to 12 volts and the fan did work, but it wasn't blowing anymore than about low. I was able to slow it down even further by turning the pot down.
I repeated the above tests with another used blower motor resistor I got from a junkyard a few years back, and the results were the same. Possible that both of them are bad, it just seems strange.
I'm wanting to call this a bad blower motor regulator, but wanted to run this past you all and see if I missed anything. Also is the regulator that Autohauzaz sells any good? Says it's an ACM OEM, what ever that means.
Thanks in advance!
Working on the blower motor in my 93 400E, and I'd like to run my thoughts past you guys to see if my diagnosis is on the right track.
High fan speed does not work when selected on the PBU, nor does the fan go to high when defrost is selected. It only runs in low, so very little air is moving through the vents. Wiggling the ignition switch and slightly turning it back towards off doesn't change anything, plus the I did replace it a few years ago as well.
Fuse F15 on the drivers side shock tower is confirmed good, so I pulled the blower fan and regulator out to test them, but left them connected to the car so I could test the circuits at the regulator. I attached the blower motor to a block of wood and set it on the engine so I could test everything under load, and get to the regulator with the fan running. On the yellow wire at the regulator I"ve got 9.13 volts on high, 4.41 volts on Auto, 1.5 volts on low, and 3.3 volts when in defrost. I took the connector above the brake booster apart and removed just the yellow wire pin to test the motor. Jumped across the blue and black wires at the regulator, and the fan runs in high like it should, moves lots of air. Voltage drop from black wire on regulator to ground is .2 volts and red wire on regulator to F15 fuse is .3 volts. Red wire on regulator to B+ at distribution lug behind the ECU in the cowl is .8 volts. That says to me that the fan itself and the circuit supplying it are good.
Just for grins, I took a variable resistor and supplied the yellow wire to the regulator (de-pinned from the connector above the brake booster) with varying voltage up to 12 volts and the fan did work, but it wasn't blowing anymore than about low. I was able to slow it down even further by turning the pot down.
I repeated the above tests with another used blower motor resistor I got from a junkyard a few years back, and the results were the same. Possible that both of them are bad, it just seems strange.
I'm wanting to call this a bad blower motor regulator, but wanted to run this past you all and see if I missed anything. Also is the regulator that Autohauzaz sells any good? Says it's an ACM OEM, what ever that means.
Thanks in advance!
