HVAC Low Fan Speed Problem - solved

[paperplane94]

Hi. Been lurking lately and wanted to bring to light a new issue to add to the documentation.
I have been getting intermittent operation of fan speeds 1 and 2. The usual fix is a new blower resistor which I did replace already and a new blower motor which was also changed. After this the next thing to look at is the climate control panel and the climate control module in front of the HVAC housing.

Is there anything else I should be looking at? I would like to document fixing the aforementioned parts rather than throwing in new/used parts at it whether it be reflowing solder or replacing electrical components.

The car is a 09/1994 540i with IHKR2 from Behr.

Thanks for any and all information.

[moroza]

Describe details of "intermittent". Is speed 3 affected?

[paperplane94]

OK so before I installed the new blower resistor (genuine Behr unit) pretty much only speeds 2, 3, and of course 4 worked. Sometimes I would lose speed 2. It seemed that the longer the blower was running the greater chances were that the lower speeds would work but I never got speed 1 to work.

After I installed the new resistor speed 1 still did nothing until today after running the fan on speed 2 for a 20 minute drive speed 1 decided to start working. I could feel the fan at speed 1 at a stoplight with the car at standstill.

Gonna see if fan speed 1 will work when I get to the car after it has been sitting with no HVAC use. If its nothing again then I will start taking modules apart.

[paperplane94]

I just ran out and tested it. No fan speed 1 after the car has been sitting for a bit. I'll make sure its the same on a cold morning.

[moroza]

I bet it's bad contacts at the fan switch. Verify by checking voltage at the resistor harness plug. Speeds 1, 2, 3, and 4 are black, green, blue, and green/grey wires, respectively. Each should have +12V when that speed is selected and the ignition key ON.

[paperplane94]

Great! I'll start there.

[paperplane94]

I bet it's bad contacts at the fan switch. Verify by checking voltage at the resistor harness plug. Speeds 1, 2, 3, and 4 are black, green, blue, and green/grey wires, respectively. Each should have +12V when that speed is selected and the ignition key ON.

Sorry it has been so long. I disconnected the connector at the resistor and each pin has 12 volts as you said upon selecting the respective speeds. Plugged it back in to the new resistor and still no speed 1.

Going to look at the schematics and try to trace it out before moving on to tearing into the ihkr module.

[paperplane94]

Hi
C5A61AA7-C3A9-40CF-B459-EDF084430289.jpeg
0D9D0551-C37A-4A4D-BCBA-E8AF8D302269.png

From the diagrams it looks like blower speed control doesn’t even pass through the ihkr module.

I am stumped.

Haven't I verified that the fan switch works already? I guess I can check the fan switch at the panel locally.


I should probably mention that I have also been having issues with the blower fan relay(k4). Sometimes the entire climate system shuts off and I have to open the hood and tap on the relay to get it to work again. It’s not repeatable when it happens, but it does happen quite often. Maybe I should try a new relay?

any advice is appreciated.

[shogun]

Testing http://www.nmia.com/~dgnrg/page_20.htm
so far in the past 10 years I have found on my car and others following problems
-broken wire from fuse box to aux fan
-melted wires and fuse holder from fuse box to aux fan as the fan's magnets got lose and movement got heavy
-contact problems for the 2 relays pins, contact enhancer solved the problem
-the last prob I had some months ago, the plug which goes onto the aux fan had one pin of the 3 pins a bit lose and that female pin was moving/shaking on the male pin on the fan side and the 12V melted part of the plastic plug + over then some time later the power did not arrive at the fan. Fixed that pin and cleaned up the plug and fan worked again.
The aux fan always works in low when the AC is switched on, and depending on temperatures of the coolant measured at the sensor on the radiator.

as the bmw4life website does not exist anymore, I could recover some with the wayback machine, copied here, the pics are unfortunately NLA https://web.archive.org/web/20130825...om/auxFanR.htm

Auxiliary Fan Resistor (Magna)
Is your AC system in good condition but not blowing cold air while sitting at a stop slight?

Check if the aux cooling fan is running. The aux fan also serves as a backup for the cooling system, when the temperature reaches 196F (91C) degrees the aux fan will spin in low speed, when the temperature reaches 210F (99C) the aux fan should spin in high speed mode. The aux fan located right in front of the condensor. You can visually see if it's running by taking a look at your kidney grill, it's right behind it.

If it isn't running, open the hood and remove the cover behind the right headlight. There's a temperature switch located on the right top side of the radiator. Pull out the connector. The following information is from the Bentley E34 manual page 170-4:
If the runs only when powered directly by the jumpered connector amd hot coolant is circulating through the radiator, the radiator switch is faulty. Use a new gasket ring (or crush ring) when replacing the switch.
Wires jumpered............Test conditions......Test results
Violet/grey and brown......ingition ON.....fan runs on low speed
Black/grey/yellow OR ignition ON.....fan runs on high speed
Black/grey and brown

If the fan does not run when powered directly, check for battery voltage at the switch connector with the ignition on. If battery voltage is not present, check fuse #29 (low speed) and fuse #25 (high speed). If no faults are found, remove the relays and turn the ignition on. Check for power at terminal 30 an terminal 86 of the relay block with the ignition ON. Fix any wiring faults found.
If the fan operates only on high speed and no electrical faults have been found up to this point, use an ohmmeter to check that the fan resistor is not electrically open.
Italian for: the resistor might have crapped out. (This would be the point where I'm not quoting the Bentley manual anymore.) The resistor runs very hot which, I would think, makes it common for them to blow eventually. The following write up assumes the magna brand resistor, located at 4'o clock relative to the aux fan as opposed to the Bosch brand resistor, located on top of the aux fan (Bosch and Magna are NOT interchangeable).
1.(I jacked my car up and put it on jackstands to have some more manouverability, probably not necessary though.) Take your license plate off and its holder and then rip off the center front bumper cover
2. Locate the resistor.
3. Remove the current resistor and cut off its connecting wires. Install the new resistor, I got mine for $34.95 at Bavarian Autosport .
4.When done with installing and connecting the new resistor
Start the engine and turn the AC on to check if the aux fan comes on.

https://web.archive.org/web/20070429....bmw4life.com/ all articles here with the wayback machine https://web.archive.org/web/20070520...om/repairs.htm

[paperplane94]

Shogun. I think you might be talking about the auxiliary fan, not the hvac blower.

[shogun]

Yes, was talking about aux fan, not blower fan.

[paperplane94]

Yes, was talking about aux fan, not blower fan.

My aux fan works on high and low.
I'm not sure how this is related.

Great website though. Sad to see it isn't live anymore.

[demetk]

To test if the switch is faulty you can unplug the switch and jump the pin with the green/brown wire with each pin on the connector. The contact points on the switch can be accessed and cleaned with some very fine sandpaper.

[paperplane94]

KISS.

As promised here is a little write up on how to clean the fan switch contacts.
Needed:
-Jewelers Screwdrivers
-right angle pick tool
-fine sandpaper on a stick or fiberglass pen


IMG_0813[1].jpg
Set multimeter to DC amps and short the relevant pins to the fan speed being tested. You may get a spark.

Realize that the switch is bad (that is if you have a good resistor in place) and unscrew it from the climate panel. The switch cannot be taken apart without breaking the melted plastic.
You can at this point think about replacing the climate panel or maybe just the switch itself, but that is not why we're here.

IMG_0817[1].jpg
Here are the switch contacts in the 0 or off position. Notice how they are all open.

IMG_0818[1].jpg
Here it is again set to speed 1. Note that the rightmost contact is now closed. So on and so forth for the other speeds. The fan would not run even though this contact was closed so it was time to clean the contacts.

IMG_0822[1].jpg
I opted to use a fiberglass pen which I use for rock chips. It was just barely small enough to fit through the gaps in the plastic housing. You may also try gluing some sandpaper to a very slender stick.

IMG_0823[1].jpg
Use a right angle pick or similar tool to carefully press down the contact from a neighboring gap so the pen can fit in between the movable contact and pin.

That's it. Sand away and test as needed.

[moroza]

Good stuff. But why the ammeter? Most can't handle more than 10 or 20 amps, and this is a 30A circuit...

[paperplane94]

Good stuff. But why the ammeter? Most can't handle more than 10 or 20 amps, and this is a 30A circuit...

Convenience. Whoops, good point.

[paperplane94]

To add to this thread the problem reoccurred and cleaning the contacts did not seem to improve the intermittent operation.
I found the plastic of the switch housing loose and surmised that was part of the issue.

I ended up getting a used blower switch from another junkyard climate panel that I had and so far low speed is good.