Begging for help! - A/C blower

[635911]

Hi All,

This is driving me absolutely crazy. Please help.

It gets hot and humid in Sydney. Last year I did the full rebuild on my A/C. New Sanden compressor. new lines, new condenser, new Tx valve, new receiver/dryer, cleaned evaporator box, flushed evaporator and hard lines, lubed blower spindle. Plus 3M Crystalline tint. It is freezing in my car!

Until this summer (ie started a couple of months ago. Now into low 30 deg C.) Smoked the controller transistor. Both fans only operate on high (ie bypass the transistor with micro-switch). I have searched widely. read everything I found. Tried putting in the upgraded transistor. No luck.

Found a second hand part, put it in....yay, it works! for about three weeks, until that terrible smell again (melting PCB) and no fan control. Fan seems to run strong all day on micro-switch max. no bearing noise etc.

Last night I buy more transistors and alloy sheet, pull out the speed controller, fabricate a lovely/complex/as big as I can fit in the box alloy heat-sink, use silver paste to mount transistor etc.

Plug it all back and trial. Seems OK at first, then gets erratic in control, then smoke comes out of the controller box. It's all over in less than a minute.

I switch everything off, remove the wires, pop the box open and the transistor looks OK, but it and the heat-sink are still seriously hot.

So why is the thing getting so hot? Something pulling too much current? Fan motor? How do I find this fault/ test the fan etc? It will cost $400 to buy a brand new controller from the US, and I do not want to blow it up/keep tearing my dash and brain to bits. Is an e28 resistor pack more robust/reliable? Can it be made to work? I could easily live with three speeds (that's 300% better than what I have now!)

I have the ETM, I have had all the bits out of the car. I am willing to go to considerable effort and cost to resolve once and for all.

Any help in diagnosis/repair gratefully accepted. Referrals to a good therapist might also be required.....

Thanks for listening.

Toby

[raykoke]

my guess is the fan motors get old and their internal resistance increases.

And then the smoke comes out.

Good luck,

Ray

Replacement-Lucas-Wiring-Harness-Smoke.jpg (62.95 KiB) Viewed 6708 times

[daz635]

Hi Toby

Good to see another 6 series owner from OZ

Does the fan controller burn out / get hot when operating the heater fan or just the A/C fan ie can you isolate it to one or the other fan motors

Sounds to me like the motors are drawing too much current

The blower motor for the heater and the A/C I believe are the same Bosch 0130063013. They are well under $100. However removing and refitting the fan cages may be an issue

If you want to try and get a second hand unit (motor and cages) complete contact Addam Smith at BM Wrecking on the Gold Coast

https://www.facebook.com/BMWrecking-Gol ... 960016698/

FYI Try Schmiedman for the Fan Speed Controller 61311381317 https://www.schmiedmann.com/en/catn-or?q=61311381317

[635911]

Hi Ray and Daz,

Thanks for your helpful (yes, needed a laugh Ray) responses.

Daz it does only happen on A/C. Thanks for the lead to Schmeidmann for the switch. that is better(???) cost.

Anyone else care to input?

Thanks,

Toby

[baders]

The same controller is used for both the heater blower and A/C. Beg, borrow, or steal a DC clamp ammeter to measure current the motor is pulling.

[kevmills67]

sorry for the response three years later, hopefully you got it resolved but for others who may be viewing these for the first time, what did you end up doing? My two cents, seems like you are getting too much current through the controller. Micro switch I am assuming is running through a fuse? Odd that the fuse for the controller doesn't go out before our controller is melting down. So assuming you are running it through a fuse at the proper amps and it is not blowing the fuse?

[635911]

Two weeks not three years. pretty good response time!

Thanks for your thoughts. The car is stock, so they should run through fuses. but they don't blow. however, there seems to be a lot of similar tales out there, so wondering what is next.

Thanks again,

Toby

[jps635]

Last night I buy more transistors and alloy sheet, pull out the speed controller, fabricate a lovely/complex/as big as I can fit in the box alloy heat-sink, use silver paste to mount transistor etc

I'm not that electrically savy, but could it be the silver paste you are using is not working as a heat sink? I've used white dielectric paste with no issues. See this http://audiokarma.org/forums/index.php? ... te.337479/

[Mamod17]

Hi Toby, how did you go resolving your problem? It's been hell in Sydney this year - 40 degrees tomorrow and my air con is a mess. Can I ask where you had yours fixed and were you happy with the service? - Guide on price would also be useful if you're willing to share!

Cheers

Denis

[635911]

Hi Denis,

I did most of the work myself. Sourced a parallel flow condenser from the US ($100), a genuine Sanden compressor from Brisbane ($240), new TX valve, receiver etc from Pelican, compressor brackets($50) from dmetek (?sp?) on the e28 forum.

Pretty simple to take everything to pieces, clean the evaporator, reseal etc, then just to the A/C guy for new soft lines, flush and gas with new refrigerant (~$500).

I followed a mashed version of a couple of write ups here and on e28.

I really recommend it, was pretty easy, wasn't too expensive (ask me about doing my 911!!!!), and works brilliantly.

I also has 3M Crystalline tint put on, which was pretty pricey, but truly unbelievable performance.

Do let me know if you need anything else.

Toby