cobalt

I spent the other night installing the new Nakamichi head unit to replace the CD-2 unit. Sound is 1000% improved and I don't even have the amp for the 6.5 mid subs installed yet.

Well needles to say no matter how careful I was, I now find that the blower only works on setting number 4. It also works on defrost and on recirculation. I checked the fuses and the relay and all checked out fine. The switch itself is working according to the wiring diagram. Also all speeds were working perfectly the last time I used the A/C.

I appear to be left with the resistor pack as the culprit. I am assuming the resistor pack is the unit directly below the radio behind the rear A/C fan speed control. It looks like a transformer with a series of resistors attached?

Is there a way to test this to verify if it is damaged? Any input on what may be the problem or may it be something else?

The a/c works great so long as I have it on speed setting 4. Too loud to be enjoyable.

Also when the A/c switch is depressed is it suposed to illuminate?

Thanks

jeff jackson

On my car... (86.5 928S), the resistor pack is in the cowl, adjacent to the front AC units expansion valve. What you are looking at... (next to the transformer in the console, is probably the vacuum solenoid manifold. Theres about 5 solenoids in a row directly behind the transformer behind the radio.

jeff jackson

PS..the resistor pack is also concealed inside the blower to evaporator plastic ductwork. It can be accessed by removing 2 retaining screws from the cowl (under the wiper motor cover) and next to the wiper motor proper, in the blower ducting. This assembly is covered in detail in the Work Shop Manuals under the heating and air conditioning chapter.
Best Regards...

cobalt

Jeff,

Thanks for pointing me in the right direction. I wasn't sure were to look. I figured it was behind the radio because i assumed I must have damaged something during the radio installation. Strange that it would just quit like that.

borland

This is a common problem with these cars, as the milage accumulates, the air flow thru the climate control system becomes restricted by road lint that builds up on the evaporator. Since the resistor pack relies on air flow to keep it cool, it will over heat and cause fan speed problems.

When you remove the resistor pack, look down inside the same cavity and see how difficult it's going to be to clean. Once you restore the air flow, you'll have plenty of airflow at speeds "1" and "2".

borland
90' S4, Slate Metallic

ColinB

Anthony
Had the same symptoms on my '89. The culprit was, as you suspect, the series resistor which is located more or less on the centre-line of the car inside the duct from the blower under the thin plastic cover ahead of the windscreen. It has a six (maybe eight) pin connector and is secured with two screws. To access it you can prise back the rubber seal between the blower casing and the duct just enough to get a small hand and forearm inside. It's difficult and it cost me some skin. A 12-year-old child would be a suitable tool for the job. The resistor pack has a bi-metallic contact designed to shut off the power if the coils overheat. Mine was badly carbon-fouled and making poor contact.

To reinstall it I fed a length of string back through the duct with a stiff wire, attached the resistor and pulled it back into position.

Colin 89GT

NickT

I replaced the resistor pack on my '88 and it burned out again within a few weeks.

Check your blower motor to make sure it turns easily. Turns out my blower won't start when in the "0" position, thus my pack burned out again. I found that there is some resistance when I try to turn the fan cage by hand. Have to pop the hood off and pull it and give it a good cleaning.

I rewired the resistor pack connector to make the "0" position a true off. (Move pin 3 to 4 if my memory serves me)

The fan took 15amp when running at full speed.

HTH

Normy

Sorry, I don't have a pic of the resistor pack itself...but it is a simple device- a board, a connector, and four springs. Check the resistance of each spring when you manage to get it loose. Word of warning: This is an air-cooled device- it sits in the air stream uncovered for a reason: It operates nearly red hot! Make sure your car is de-powered while you are doing all this.

This is a bit of a trick. You'll have to remove it from inside the air conditioning duct. To do this, pull the rubber connector "sleeve" [green arrow] back and work your arm in behind until you can feel the resistor block [red arrow], which is held in by two screws. Undo the screws and try not to drop the resistor on top of your evaporator! Remove the resistor pack by pulling it out through the pulled-back sleeve. It helps to have small arms for this job.

Once you have it out, take a look in the resistor hole and see how dirty your evaporator is; Now would be a good time to clean it out.

Good luck!

N!

cobalt

Great info guys. Although the fix sounds comperable to brain surgery through the nose. One thing I don't have is small hands and arms. I may need to employ my 7 year old son on this one. He will be happy to take the car apart. Now is when I wish I had a 94 with the pollen filter, I think it would have made access much easier.

It appears the fan itself is working fine but I will double check while I have it apart. I will definately clean everything while in there.

Before this happened the flow at low speeds was fine. The last time i had the car out I was sitting in bumper to bumper traffic and the outside temp sensor was reading 105 degrees. I may have damaged it then without realizing it, I just found it strange that it appeared to be working and then I changed the radio and it stopped. My wife says it is the car knowing I messed with it.

I will attempt this tonight and see what I can find.

thanks

SharkSkin

Folks with large hands can get to this by removing two mounting bolts for the fan from above and one from below, and shifting the fan housing out of the way. No need to remove the hood.

Ed Scherer

Well, I don't have much to contribute to this thread, but I replaced my resistor pack a few weeks ago while fixing my intermittent blower problem. My problem was actually due to a bad connection at connector J23 at the central electric panel, but in the course of tracking that down, I noticed that my resistor pack was missing its cover. I happened to have a brand new spare handy, so in it went. I think I lost a bit of skin doing the replacement, too. I'd have to say that it wasn't as hard getting the resistor pack out and replaced as I was expecting, based on what I had read about this job. Did the "fish in the replacement by pulling it back to the mounting hole with a stiff wire" method, and it worked fine.

The only thing that added a bit of time to this job is that I dropped one of the mounting screws and washers into a rather inaccessible location right under the mounting area. After about 15 minutes of fishing around with a magnetic pick-up, I finally retrieved them. Along with another mystery washer from someone's previous adventure.

Oh, and I snapped some photos of the resistor packs (both the old one without the cover and the new one). Click the photos for bigger versions.

cobalt

I would have to disagree with you there. You actually gave me more info than you realize. I now have an idea of what i am looking for and a part number which always helps.

Now that you mention it I may have disrupted a connector while doing the stereo install. I will put this first on my list of things to check.


Wouldn't be a proper repair without loosing some flesh in the battle. I am lucky I heal easily otherwise I would be permanently scared from all the scrapes and cuts I received working on Porsches over the years. Most of the scrapes came from locating that irritating screw or nut that got away.




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Thanks for all that info I think you helped more than you realized.

jeff jackson

Actually...since this part is around 10" or so down the blower to evaporator ducting from the aforementioned "access" sleeve...and not an easy grab for the "normal" adult male arm...I did alittle research on the matter, and found, that with a small but strong magnet, attached to a coat hanger type rod...once the electrical connector is unplugged, and the screws are out...the unit can be extracted without any fleshulary abrasion.... YMMV

borland

No small arms needed. With a claw type of pickup tool, the resistor cage lends itself to being retrieved from the cavity.

For the replacement installation, you can pull a length of cord thru both holes, the with one end of the cord looped thru the resistor pack cage, pull the resistor pack in place. After attaching a couple screws loosely, remove the cord or string and finish the installation.

borland
90' S4, Slate Metallic

cobalt

.Just want to thank everyone for their help. Made the fix a piece of cake.

The problem ended up being the contact points on the resistor pack Terminal #8. They built up corrosion over time. Removed the cover and used contact cleaner and some Emory paper to clean them and it works like new. Porsche could have made access to the resistor pack much easier than they did but what can you do.

All the ideas to access the unit really helped, you guys are the best.