help: inside compartment blower fuse..blowing

[bigchillcar]

problem somewhere with my climate control unit. the fuse for the fan blower in the car has blown twice in the last two weeks (25 amp). i replaced it the first time with another 25 amp and it lasted a week or so. today, the fan would only blow weakly and it didn't change from position 1 to 4 on the dial?? turned on the a/c and it popped. i put in a 20 amp, as it was the only one i had handy and it popped as soon as i turned the fan on. should i try a 30 amp? how far up would you go in amperage? i know this isn't a good idea..obviously the ccu is drawing too much power for some reason. any ideas why??

[bigchillcar]

found this at: http://www.systemsc.com/technical.htm....looking for clues:

Fan speed control in most climate control systems utilizes some form of a servo amplifier. The output
of the amplifier provides a variable ground which varies the fan motor current, as the input voltage
from the control head is varied. The motor current is sensed and provides feedback to stabilize the
actual motor speed based on the selected motor speed in the control head. The fan speed control
unit is usually placed within the fan blower housing to provide cooling for it. In some applications,
the fan speed control unit may have a large heatsink and be attached to the body, e.g. the Porsche
964/993. Because of the fan motor current (about 10 amps or more) and the power (25 watts or
more) being dissipated by the amplifier, the fan motor amplifier may fail keeping the fan motor from
turning off.

[bigchillcar]

sometimes my fan wouldn't turn off either. if i shut off the car and restarted, sometimes it would be off then, but only until i turned the car off..

[kirkf]

Most likely your fan blower motor is seizing.
Dont put in larger fuses. Eventually you are just going to burn up a pile of wiring, which is going to be god awful expensive to replace.

Kirk

[bigchillcar]

hi kirk,
thanks. that's what i'm leaning towards, too..and i agree with you. larger fuses will eventually spell trouble. the fan blower is probably failing and stating to draw more power as a result. if this is that $450 fan i think i'm going to just ****....

[Don Plumley]

Ouch. I'd be thinking a lot about how to rebuild the motor or cobble together a replacement from the McMaster Carr catalog...

Hi Ryan, recently had one of my motors start to squeal, here's a procedure of what I did to fix it. Might help you to free up the motor and get it going again.

I don't know it this will work, but here goes.

Temporary Fix for a Squeaking Forward Air Conditioning Fan Motor

Recently while driving my RSA on a Back Country Tour it was hot enough that I decided to turn on the Air Conditioning. During the initial cool down with the fan set in position 4 all was working great. When the temperature was lowed to a comfortable level I shifted the fan speed to position 2. Within a few minutes I started to hear a low squealing coming from the a/c fans. Sounded like the bearings in the drivers side fan motor. Very annoying to say the least.

When I arrived home, I removed the front trunk cover that covers the a/c module and took a look at the fan motor using the Porsche Pet Parts Manual as a guide. The fan in question was quite buried to say the least. I called the local Porsche Dealer for a price on a new fan motor and the quoted price was $560.

I’ve had some experience rebuilding 12vdc motors and know of a few shops in town that I’ve used before to rebuild 12vdc motors. With a prohibitive replacement cost of $560, I planned to remove the fan and rebuild it. I found a 993 a/c evaporator procedure on line http://www.p-car.com/diy/ac , this reference had a lot of great information, but required the removal of the hood, gas tank, fuse box, a/c module, etc. Definitely further than I wanted to go.

The driver’s side fan motor has the a/c line routed very closely over the fan motor cover. I also didn’t want to have to drain down and recharge the a/c system, the question was will it move enough to get the fan cover off.


1. Remove a/c compartment cover.
Remove 2 a/c hose mounting clamps.


2. Remove 4 silver clamps holding the fan motor front cover in place. Use a long thin screwdriver and a magnet to catch the clamps.

3. The fan motor cover is ready to be removed. Using just your hands, pull the a/c hoses out of the way and remove the fan cover by pulling upward. Not really easy, but it will come out.

Note: There are 2 T20 torque screws holding the fan motor in the a/c module, the fan motor impeller is notched for access to the screws. You can not see into the fan impeller to see the screws, you have to use a mirror. Do Not remove these screws. I removed the screws to get the fan motor out, the fan motor is wedged into the module and further disassembly of the module is required. I’m still working on how to do that without major component disassembly.

4. Using the syringe filled with oil, inject a few drops into the front fan motor bearing. Turn on
the motor at low speed and run for a few minutes. Stop the motor and inject a few more drops of oil into the bearing, test again, you’re done. I used Caterpillar Penetrating Oil with Moly p/n 1U-8265.

5. Replace all parts in the reverse of disassembly and the squeaking is gone for awhile. So far I’ve run the motor over 48 hours at low speed with no squealing.

Note: Use double sided tape on your fingers to hold the silver clips for installation. Place clip on the tape, position on a/c module flange and push, they pop into place. A arm with 3-4 universal joints would be helpful.

Well, it got all the text, didn't get the pictures. Hope this helps.

Good Luck, Don

[bazar01]

You must have a long and slender arm and fingers.

[bigchillcar]

put in a fresh 25-amp fuse and so far it's holding up. where is the inside compartment blower located? is it the one that you access through the front trunk area that's a real bear to get to and does cost around $450?

[bigchillcar]

don - thanks for the very informative post! i didn't see it..just replied to my own thread which had been open a day or so and hadn't refreshed the page, so i thought i was the last post. i do hear squealing sometimes on the passenger side blower. i've found that if i turn on the defrost button for a few moments it spins it up fast and sometimes perhaps 'reseats?' the fan and it stops squealing, at least for a while. do you think this procedure would be more difficult then for the passenger side. granted, the real problem i have right now is an intermittent blowing of the blower fan fuse. my squeal is not too bad and i often don't hear it over the stereo anyway.. but i'm thinking that my blower motor is starting to draw more power due to resistance somewhere? and that may be what's causing the fuse to blow. it's always happened on particularly hot days, too. maybe the blower motor, when it can't dissipate enough heat, pops a fuse. wonder if it has some sort of heat sink?

[bazar01]

DC motors pulling more than rated amps is usually due to worn down carbon brushes, failed rotor shaft bearings or just bad windings.
You have to pull it out to find out. Or just lube the bearings as Don suggested.
If you have a lot of hours on that blower motor, lubricating the bearings will not fix the high amp draw.

Ok here goes, yes it's the motors in the front trunk, yes, it's a ***** to get to them and I've got the cuts on my hands to prove it. At times I was laying on the fender to work on it.

For light, I took a single filament brake light bulb, soldered wires to it, and hooked it up to the battery, not enough room for a flashlight. But it does get hot, yeah.

The bearing that wears out is the front bearing right next to the squirrel cage fan, weight of the fan on the bearing. Oiling the bearing isn't a permanent fix, but it gives you time to think. The procedure works for both sides, passenger side is easier, no a/c hoses in the way.

Most likely the bearing is an oil impregnated type and it’s dried out. But I won’t know that for sure until I get one out. Maybe even find out who made it, Porsche probably didn’t. Would be nice if I could get a hold of an old one to see if I could rebuild it, maybe modify it to use a sealed ball bearing. I’ve got a lathe and mill.

Good Luck Don

[356-4ever]

I have an issue with the "inside blower compartment" on my 1990 C2. Everything seems to work well, but there is a huge parasitic draw on the battery when it is parked. I have pulled all the fuses and #1 is the problem.

I have replaced the battery and after 3 days of sitting the car will not start. If I remove the fuse I seem to be okay.

Is this drain even possible? Does the blower have to be removed to be unplugged?

[Traveller]

Originally Posted by bigchillcar

i put in a 20 amp, as it was the only one i had handy and it popped as soon as i turned the fan on. should i try a 30 amp?

No! Fix the problem by finding your excessive current draw.

I realize that is easily said as most DMMs only have a 10A position at most.

Disconnect one item at a time is another way to find the cause.

[surfdog4]

Bigchillcar,
had your car been sitting for a while? Right after i bought mine (it had been sitting with the P.O.) the blower fuse blew..i was thinking the worst but i popped in a new fuse and it has been working fine ever since.

i got to wondering if the lubricant in those motors hardens or stiffens when its not being used...i was restoring a 928 and neither window operated, but when i disassembled the window motors, turns out they had just been sitting so long the grease had hardened and siezed up the motor..once i cleaned it up and re-lubricated, they worked fine....

with that experience i try to exercise my blower fan over the whole range whenever i think about it..maybe silly but in my mind i am prolonging the fan life

[lucittm]

Replaced my blower motor and out of curiosity, disassembled the motor. (I got mine at Vertex, they had the best price)
The bearing that is pressed into the housing was worn into an egg shape and causing the armature to rub on the stator, generating drag and causing all sorts of excessive current draw. I could not figure out how to remove the bearing without destroying the motor housing so it went into the trash.