ACM aux fan dead in less than a year - fluke or quality issue?

[racer2086]

Hey guys,

I replaced my AUX fan last October. This past Friday while idling, my high pressure safety valve blew off a bunch of my refrigerant. It turns out, my aux fan is non-functional. It does not activate when the compressor engages as it should and as it used to.

So my question: is ACM a quality fan? I bought through FCP, which offers this ACM as an option to the genuine BMW fan at twice the price. I'm close to purchasing the BMW fan, as I don't want to deal with this again and being in FL, that fan is very important.

For diagnostics, I tried to activate the fan in INPA, but both of my INPA versions throw errors when I try to activate anything on that page, from the compressor to aux fan. However, when the A/C is on, INPA shows the aux fan as activated, even though the physical fan is not operating.

I will check the fuse now, but wanted to get opinions on here about ACM fan quality. Also, FCP has a Nissens fan listed for the E39. I'm not sure I want to gamble with aftermarket again. I've been having a string of bad luck with aftermarket parts lately (for another thread).

[purplecty]

Hey guys,

I replaced my AUX fan last October. This past Friday while idling, my high pressure safety valve blew off a bunch of my refrigerant. It turns out, my aux fan is non-functional. It does not activate when the compressor engages as it should and as it used to.

So my question: is ACM a quality fan? I bought through FCP, which offers this ACM as an option to the genuine BMW fan at twice the price. I'm close to purchasing the BMW fan, as I don't want to deal with this again and being in FL, that fan is very important.

For diagnostics, I tried to activate the fan in INPA, but both of my INPA versions throw errors when I try to activate anything on that page, from the compressor to aux fan. However, when the A/C is on, INPA shows the aux fan as activated, even though the physical fan is not operating.

I will check the fuse now, but wanted to get opinions on here about ACM fan quality. Also, FCP has a Nissens fan listed for the E39. I'm not sure I want to gamble with aftermarket again. I've been having a string of bad luck with aftermarket parts lately (for another thread).

You should have an error in the DME for fan activation. FCP should honor the lifetime warranty for that fan if it is bad. I used a German parts saver e39 fan from eBay which is a direct bolt on for the e38 and its been good so far...

https://rover.ebay.com/rover/0/0/0?m...2F281985795303

[racer2086]

I just check the fuses. All good.

I pulled the plug out and measured the voltage. It gets 14v on one of the pins (I'm figuring the low speed wire) when the compressor is on.

On the fan side, the resistance across the two pins (the ACM fan only has low and high speeds) is 250,000 ohms and 5 ohms. The 250k ohm pin is the low speed pin. So it seems like maybe the resistor is bad.

What I don't understand is why the car didn't flip on the high speed fan mode when the high pressure switch sensed the high refrigerant temp?

Maybe that relay is bad and my fan is bad?

I'm going to buy the BMW fan. I'm done with these aftermarket crappy parts.

[purplecty]

Why not just pull a few of the oem motors from the junkyard?

[acspecialists]

The high pressure switch should cut out the compressor before you vent. Maybe worth looking at?

[racer2086]

Why not just pull a few of the oem motors from the junkyard?

Thought about that, but they are going to be beat up and 20+ years old anyway. There are no E38s in the yard near me either.

The high pressure switch should cut out the compressor before you vent. Maybe worth looking at?

So this was my concern. And, I was talking to my dad about this...the car should have switched the fan into high speed mode at least as the pressure increased. I have never heard in recent memory my fan on high or medium. Even back with my original fan, it only ran on low. So it is possible the high pressure sensor is bad, I'm thinking?

[setconstr]

My aux fan would not work went to a few different Indies none could figure it out turned out to be corroded pins in my DME coolant can travel up your loom from the front thermostat and get into the DME its easy to check just unplug the 4 plugs and pull it out ......

[racer2086]

Will check that tonight. Good idea!

[racer2086]

Would just like to update this.

All fuses and relays checked out good. No coolant up the DME.

I started the car and ran with A/C on and it sent 14v to the aux fan, but the fan did not run.

So I bought a Genuine BMW fan to install. I just did this 2 days ago and the fan works as it should. So the ACM fan (resistor I think) burned out in less than 12 months. I will be returning that for a credit and keeping my BMW fan.

Here's possibly the more important thing: the ACM fan (and many aftermarket fans) only had 2 speeds (low and high), whereas the original BMW fan and the new one have 3 speeds.

This is important because as the WDS explains for the prefacelift cars, the middle speed is used by either the high pressure sensor in the A/C system or the coolant temp sensor in the radiator outlet.

A/C operation: When the A/C pressure climbs above 22 bar, it is supposed to kick in on that middle speed to cool the condenser and control the high side pressure. Obviously, the ACM fan is unable to do this without the middle pin and middle speed. Huge problem. That could lead to very high high-side pressures, which in my case obviously happened. I'm still not sure why the compressor didn't turn off if the pressure reached very high levels, but maybe my blow off valve is a little weak and blew off first.

Coolant operation: When the coolant outlet temp exceeds 91*C, the aux fan is supposed to kick on speed 1 regardless of A/C operation. When coolant outlet temp reached 99*C, it should be on speed 2. If over 104*C, then speed 3 is engaged. Now, with a properly functioning fan clutch and cooling system, the outlet temp probably rarely sees 91*C, as my car almost never engages the aux fan without the A/C running. The radiators in these cars are 3 row aluminum, so the coolant temp probably drops a good amount by the time it reaches that sensor (remember, we're talking a different sensor than the one on the water pump that feeds the KTEMP in the cluster).

Anyway, the fan is working great so far and my A/C works better than before. When I started the car and ran the A/C, the aux fan kicked in at speed 1. I unplugged it and put my meter on to test each pin. By the time I got done, the car had switched voltage to the middle speed and engaged speed 2 which ran as soon as I plugged the fan in. About 10 seconds after running at speed 2 it dropped down to speed 1. Therefore, my high pressure sensor works as to the relays and fan. I clearly lost A/C charge, so with a higher charge, this speed would be more important.

Thus, I would recommend AGAINST this ACM fan for E38 owners and be very careful about aftermarket options that save money by cutting out a resistor and the middle fan speed.

[purplecty]

Good information! Glad it is fixed!