[Solved] A/C not blowing, Aux Fan OK

[jac]

The cooling fins on the FSU are cylinder shapes.


BUT... The damn blower fan has stopped working just 2 days later. sigh.

So, I pulled off the FSU, crossing fingers that the FSU was just dead, and tested the blower by jumping the connector pins again... but this time the blower does nothing...

I am hoping I am using the correct connector diagram please see photo below.

I do measure battery voltage between pins 2 and 4 on the connector, even when the engine is off and key off the ignition.

The resistance across pins 5 and 1 on the connector changes, so I assume the blower windings are broken and the blower fan is dead. :-(

The resistance across pin 5 and pin 1 is low if I let it sit there for a while, I get like 10 ohms or so. But, if I then apply voltage to those pins then the resistance climbs to 7.5Kohms.

Anyone know if pins 1 and 5 are directly connected to the blower? or is there any other electronics between them and the blower?

[andrewwynn]

I would try to spin the blower by sending a jet of air down the dash vent. Blow mode of vacuum or maybe leaf blower. Do while measure volts on blower ±. It should generate some voltage. I do not think there's any Electronics from that connector to the blower. You may be experiencing a dead spot. If you get the fan to turn a little and get it to run, take a reading of AC volts on blower it should be almost zero. Even better if you have oscope. Open commutator or winding will create voltage spikes.

I just looked up to the top to see what forum. E53 is much harder than e70 to deal with blower motor. I think I'd have a portable vacuum in my car to jump start the blower for a while before I tore the dash apart to swap blower.

[jac]

I will try blowing into it with the shop vac exhaust :-) Thanks AndrewWynn!

[jac]

Blew air into the center vent on the dashboard. I could feel the air coming out of the vents near the doors. As air was blown into the vent, there was no A/C nor DC voltage across pins 5 and 1. :-(

I did not connect the oscilloscope, just the fluke digital multimeter.

I guess that's confirmation that the blower is gone?

[andrewwynn]

It's hard to say if you actually were able to spin the blower. You can have DMM set to Ω also to see if the reading changes. I never took that motor apart to know the brush/commutator configuration but I'm pretty sure it's a common permanent magnet DC brushed motor.

At end of life it's very common for a winding to become detached from the commutator bar and gives you a dead spot. The goal is to get the motor to turn even a litte off the dead spot.

If the outside air vent is open just driving can freewheel some blowers add well as using shop vac air from below the outside air intake filter.

On some cars you can see the squirrel cage from under the hood with the intake filters removed. I don't remember if e53 is included.

[wpoll]

Originally Posted by andrewwynn

... On some cars you can see the squirrel cage from under the hood with the intake filters removed. I don't remember if e53 is included.

I haven't tried this but if you remove the cabin filter housing (under the bonnet/hood) it's likely you can get a (gloved!) hand in there and spin the blower cage.

[andrewwynn]

I was thinking stick! The FSU is always powered hence the glove.



Maybe with a flexible wire like copper solid electrical wire you can get though the center vent into the blower. If you can turn it just a bit and it fires up you can basically confirm that's the problem.

[jac]

That's a great idea. I will give this a try, but I am away now for some days so I will report back when I return.

Thanks!

[jac]

I was finally able to get to this again and confirmed that you guys are geniuses.

I removed the A/C filter in the engine compartment along with the plastic housing surrounding it. That gave me free access to reach and spin the blower motor with my fingers.

I spun the blower motor while the car was off and then went inside to turn on the car and the A/C came on and so did the blower.

So, I now know the A/C system works but the blower has a dead spot.

However, I've only been able to get the blower to move off its dead spot by spinning it with my fingers (and not via an "inside the cabin method"). So, I am likely going to take on the bear of a job of replacing the blower motor. The heat here is unbearable and besides, I now have an unexpected extended period of "free time" ;-)

I am gonna start searching for guides on doing the blower replacement procedure, but if you happen to know of a good one, please send it my way!

Thank you all!

[andrewwynn]

That's great feedback to confirm dead spot from under the hood.