'85 Front Condensor Blower Fix

[Discseven]

When the AC's on… the front condensor blower makes just enough noise to be heard when standing near the front bumper. Mine's silent so something's not right.

I’m diving into it to see if I can sort out the problem. First a check to see if there’s power to it. There is.

Here’s the blower in parts… Not much to it.



Tools used: small flathead screw driver, Phillips head, sharp scraper, small metric Allen wrench, small drill bit, Xacto knife and something to cut on. Penetrating oil, 400 grit (or thereabouts) sand paper, anti seeze and nail polish are also used. (I’ll cut some wires and crip new terminals and cover them with heat-shrink tubing but this is not absolutely necessary. To test the junction, a simple electrical tester is used.)


REMOVING THE BLOWER

My battery and spare tire are out so access to the blower is easy --- I believe the spare must be out to pull the blower. The electrical service junction near the blower is disconnected. The 4 metal screws that secure the blower to the chassis are removed and then there’s a sticky seal has to be scrapped to free the blower.

This blower takes air in from the space behind the front bumper. Its intake nozzle is positioned through a hole in the body’s forward bulkhead. The silver painted section (seen below on the blower) is what sticks out ahead of the bulkhead when the blower is installed.


PARTING THE BLOWER

There are two halves to the blower that are held together by four clips. These clips are easily pried off with a small flat screw driver. Protect your eyes when prying these clips off as they can bullet off if they release just right. The impeller here spins freely.



The motor releases from the housing by undoing a single Phillips head bolt located on the circular metal plate. Once this bolt is removed, the motor slips out with the aide of feeding its electrical cable in through the grommet hole to follow the motor. I’ve pushed the grommet in with the cable.


MELTDOWN

With the motor in hand, it’s easy to see that both plastic brush casings have melted. The deformed brush casings have disconnected the brushes from the commutator and so put an end to this motor motoring. The cause of the meltdown is unknown to me. Do you know what would cause the heat necessary for this meltdown?
___

A closer look at the toasted bush assembly. The good news… Bosch still offers this motor. Pelican has it.

Impeller comes off the shaft next. A hole in one of the impeller blades provides access to an Allen set screw in the collar.



In this case, the Allen is covered with a hard redish substance.

A drill bit is used to break the substance up --- I’m careful NOT to bore out the Allen. Assuming this “sealer” was placed to prevent corrosion… it worked. After 33 years in service, this Allen’s still in excellent condition.
__

Once loosened, the Allen set screw comes out easily.

Getting the impeller off the shaft does not go easily. Looking at the exposed tip of the shaft, and in particular where shaft and impeller meet, the corrosion here has likely expanded the end of the shaft and fused the parts. Penetrating oil and a little abrasion to the seam where impeller and shaft meet serves to “shrink” the shaft… and the impeller comes off.



Male and female terminals exist on the service wires to the motor so the electrical connection to the motor can only be made so the impeller spins in the right direction. A test of these wires conductivity says the wire’s good. I’m going to cut off and replace both terminals since it’s easy to do and they're right at hand.

Before being too pleased with the arrival of the new motor, a few questions are answered: Does it fit in the housing?… is there a tapped bolt hole in it that aligns with the securing plate’s hole?… does the existing Phillip bolt fit it? Yes to all.
__

New terminals have been installed on the service wires and insulated with a heat-shrink tubing. (On this motor, the positive side has a RED covered wire (seen below) leading to the terminal. The negative side has no covering. The brown part with the copper coil sitting in it is the plastic brush casing that suffered the meltdown in the old motor.)

The motor is now inserted into the blower housing with the motor’s securing hole aligned to the hole in the exterior metal plate. While inserting the motor, it’s necessary to pull the electrical cable out of the grommet hole to get the cable out of the motor’s way --- there’s no space inside the housing for extra cable. The cable’s grommet is reseated in the housing. Then the motor is secured to the housing with the single Phillips head bolt and lock washer.



Anti seeze goes on the impeller shaft and the threads of the Allen set screw.

The impeller is placed loosely on the shaft… and the housing’s halves are joined only in order to position the impeller on the shaft to operate with maximum efficiency --- I like the open intake face of the impeller being very close (1/8”) to the inside wall of the housing half that covers the impeller. The Allen set screw is then tightened but not all the way yet.
__

Before closing and reinstalling the blower, it’s connected to the car (the battery temporarily reconnected) and the AC is turned on and off a few times to make sure the blower works AND the impeller spins in the right direction. It does. The Allen set screw is now fully tightened, and, to continue the tradition of protecting the Allen’s slot from corrosion… a drop of nail polish goes in the Allen slot.

The channel in the housing half where the rubber snake seal goes is cleaned and the snake seal reinstalled. I use zip ties to secure the housing halves together. The original retainer clips will be treated to remove the rust on them... then stored for a potential restoration at some later date.



The seal between the blower and chassis needs to be replaced. I’m using ¾” x ¼” hatch tape (from Home Depot). This material cuts easily with a sharp Xacto blade, only one side is pre-glued so positioning the blower is a simple matter, and the soft foam compresses easily so a tight seal will occur without the need for double-sided adhesion as the prior seal provided.
__

4 new stainless washers and metal screws secure the repaired unit… electrical service is reconnected… and the blower’s back home in working condition. All told, this was a 4 hour project including the trip to a nearby Home Depot for the hatch tape.

Is the AC blowing cooler? I believe it is ~




BACK END NOTES

Electrical motor works:



This vid is far more informing than the illustration above: DC Motor - YouTube

[Richwro1]

most folks re-wire the power from the fuse block to another fuse as this motor is sourced from the same fuse as the evap blower. When evap fan is on full speed, it and the front condenser suck up max amps at the 20 amp fuse and it has a habit of melting. They also add another separate fuse on the power line to prevent a fire if the front condenser fan freezes up in the future. Of course I haven't done this yet, so I speak easier than do. But after all the great work you did, you may want that extra sense of calm

[Discseven]

Nice note Richwro1! This goes on the to do list. Thanks!

[wwest]

"..heat necessary.."

You don't say how easily, or not, the old motor would spin, could be "spun" manually.

The rust on the motor housing would indicate that this motor spent some time "underwater". That "green tint" on the connectors might also indicate the presense of water damage.

If the motor bearings did not allow the armature to rotate freely with back EMF being the primary limit to motor speed, the electrical current inflow would be extreme. At that level of current flow through the few hundred milliohms of the brush/commutator contact point resistance you can easily get enough HEAT to melt plastic.

Anytime I run across old crimped electrical connections I always take the time to solder the crimped connections.

Speaking of milliohm connection resistance.....

Take a good look at your fuse block. The "spring" connectors holding the fuses in place lose their "springiness" over time. Worth removing the fuse one-by-one and bending the connections back into, toward, more tightly "gripping" the fuse.

[Discseven]

Hi Wwest... I thought I mentioned the impeller spinning freely?!?! Maybe not. In any case... it did spin freely.

Good idea on the soldering.

I cleaned the fuse connections but did not rock them... another good idea.

Thanks!

[scottb]

These blowers have been known to seize and burn up, so Porsche developed a fuse harness that goes in-line on the power input to the fan. It's simple plug-and-play. Unfortunately, I can't seem to find the part number, but a call to our host might yield information.

Good write-up!

[Discseven]

Hey Scott... great idea on the in-line fuse! Thanks!

[scottb]

Karl: You're obviously very good at "electrics," so if the Porsche plug-and-play part is NLA, it wouldn't be difficult to install an inline fuse with a blade fuse holder from your FLAPS.

HTH!

[JAR0023]

Originally Posted by scottb

These blowers have been known to seize and burn up, so Porsche developed a fuse harness that goes in-line on the power input to the fan. It's simple plug-and-play. Unfortunately, I can't seem to find the part number, but a call to our host might yield information.

Good write-up!

Here's the part number and a link for the fuse/harness for the condenser blower motor. There is not a lot to it and it would be easy to replicate, but it does make for a clean easy install and doesn't cost that much in the grand scheme of things. -J

91161207700

Pelican Parts - Product Information: OEM-91161207700

[scottb]

For that little money, it hardly pays to DIY and splice something together, IMHO.

[rusnak]

Those front condesor blowers have a very nasty reputation for not only catching fire, but blowing fire right up into the hood. Probably one part that it's wise to just replace. I can see using a new electric motor as the OP did, but not rebuilding the old one. I also see the wisdom of spreading the loads out, and installing an in-line fuse. The Porsche website doesn't show a pic of the inline fuse, and Porsche has been stupidly slow shipping parts lately.

[redturbo911]

Revive on a helpful DIY. Thanks.

[86 911 Targa]

[steve84]

Great write-up. I tried to replace just the electrical motor over the Summer. I didn't know about using the drill bit to remove the red substance. I tried using PB Blaster and WD40, after several tries, I over muscled it, and stripped the Allen head. I wish i had seen your post then. Wound up buying a new unit for about $300.

[awhnry]

????? $300???? I paid less than $100 at an online parts warehouse not associated with this forum and it came in the Bosch box. I hate to be disloyal but it pays to shop around.

[wrxnofx]

Originally Posted by awhnry

????? $300???? I paid less than $100 at an online parts warehouse not associated with this forum and it came in the Bosch box. I hate to be disloyal but it pays to shop around.

I believe what he means is that he bought the entire motor assembly, not just the motor, like here.

The motor itself can also be purchased from our host here for under $100.

[steve84]

I was able to locate the Bosch electric motor for around $50. But since I stripped the Allen head, I needed at least a new squirrel cage fan. Failing to find one of those, I had to get a complete blower assembly, I.e., the molded black plastic with motor, fan and harness. I couldn't find one for less than $300, and even then the supply was limited to just a few. At the time, I felt lucky to be able to get it at that price, even though I thought it was a bit too high.

At times, I'm amazed at the pricing for certain parts. Smaller, seemingly uncomplicated parts cost more than larger, more complicated parts. I guess it's explained by supply versus demand.

[JAR0023]

I've found a squirrel cage fan that works as a substitute for the OEM fan only available in the assembly. It's a Fasco fan used in appliances. Part number 1-6038. I paid less than $15 shipped. It's built for an 1/4" shaft and not the 6mm one on the Bosch motor but it was easy enough to shim it with a piece from an aluminum can. The outer diameter is maybe an 1/8" less than OEM. It's rated for a higher RPM than OEM as well. No issues with mine in maybe 4k miles this spring and summer. -J

[wrxnofx]

Originally Posted by JAR0023

I've found a squirrel cage fan that works as a substitute for the OEM fan only available in the assembly. It's a Fasco fan used in appliances. Part number 1-6038. I paid less than $15 shipped. It's built for an 1/4" shaft and not the 6mm one on the Bosch motor but it was easy enough to shim it with a piece from an aluminum can. The outer diameter is maybe an 1/8" less than OEM. It's rated for a higher RPM than OEM as well. No issues with mine in maybe 4k miles this spring and summer. -J

How is this cage working out for you, JAR? I CANNOT get the cage off of the motor shaft. The allen set screw was seized, so I had to drill that out. Even still, the cage is just seized to the shaft. Short of cutting the shaft off the motor and drilling the shaft out, it's not going to happen.

[JAR0023]

So far, so good. I haven't touched it since it went in. It finally turned hot here in the last few weeks so I've been running the A/C every day. -J