AC Evaporator Blower replacement Idea

[mkc1962]

Like so many others here, that chose to keep the AC in their cars, I finally had to make a move on that noisy Very Expensive Evaporator blower. However, like so many I just could not stomach the price of that cheap looking little OEM motor. I’ve heard of the better types by Griffith? (I think it is) but then on a 87 3.2 you have that problem of having to find another evap box lid due to the size of the motor. And still you spend some pretty hefty coin. To the purists out there, please pardon me if what I am about to share offends you.

Ive been working on and restoring vintage cars for near all my adult life. And many times have had to re-engineer things to make them work better or work at all due to lack of replacment parts. Not to say that I don’t myself keep things pure when I can. But sometimes, things like this pesky blower just don’t make sense.

My thoughts/goals for my blower replacement were.
1.) For it to be VERY inexpensive and easily obtained anywhere.
2.) For it to be done with keeping the smuggler box area as close as possible to original.
3.) For it to be easily removed if and when it be needed. Meaning no Evap box removal.

I also own a mint condition 73 GMC 4x4. To keep this short, coincidentally its heater blower FAN is an exact match size wise for the OEM Porsche unit. The motor is just a tad taller. To be exact the unit I purchased is for a 90-2005 Chevy truck.( I found it to be a bit shorter than the 73)

In our P cars the blower mounts from the bottom up. The Chevy unit drops in from the top/outside. Meaning no box removal if ever needing to replace.

1.) Remove your evaporator box lid. Remove plastic plate/fan cover and fan/motor itself. Toss motor fan in nearest trashcan or use as a paperweight.

2.) Using a dremel or similar and carve out lid of evap box to accommodate the new fan blade for drop in type feature. Use original motor hole as a pattern by which to center your new hole into the overall housing. Don’t get the hole any larger than you have to in order to pass the fan in, as what is left of the lid is what holds the fan in. And you will at best have about 1/2" plus all around.

3.) Place fan into hole and mark mounting holes around perimeter. Make or obtain speaker type mounting clips to go over each mounting hole on the lid of the box and install the Blower using short sheet metal screws. You might also want to make a gasket of sorts to seal around the blower to avoid loosing any of the precious cold air.

4.) You will need to make up a short (2-3") brown (to keep the German ground color code correct) 14guage jumper wire with a ring connector on one end, and a female spade connector on the other. Place ring connector under one of your mounting screws to provide a neg ground for your new motor. Then plug your OEM blower harness's brown into this ground jumper and the remaing red wire onto the provided spade plug that is built into the new blower.

5.) on the inside of the evap box you have a plate that goes on top of the fan itself. I myself used 1/8" lexan to shim this entire plate about 1/8" father away from the fan blade. even the original was a very extreme close fit. And even my original plate and fan had done some rubbing on my plate. I Then used Thumb gum (HVAC clay type sealant) to seal entire perimeter of this plate. Caulk would work, but would be messy.

6.) Reinstall Evap box lid.

7.) I mentioned above that this motor is slightly taller than the OEM. Roughly 1/8"-3/16". I took a piece of carbon paper and placed it on top of my motor then shut the smuggler box lid and bumped it a few time to find out where if any adjustment was needed. The carbon paper will leave black marks on the box lid.Remove the smuggler box lid.

8.) Soft towel, pile of sand or sand bag, and round end of a ball peen hammer would work best. Front yard grassy spot would work too. Place the towel down, Lid upside down into towel, using round end of ball peen, re-dent the lid to make things fit. Keep doing this until you get a clearance fit and can close the lid without it hitting the motor.

9.) Reinstall lid, and once again enjoy cold air. I’ve had mine in now for about two weeks. Blows equal to or better than OEM. Now I just need to do something about those pesky useless low and mid speeds.
Main thing is I met my goals and got the system working again for pennies. First time about 2 hours. Could probably do the next in about 45 minutes.

The tools for this, any DIY should already have. The evaporator box lid is your own that you will modify. No need to buy one from an older 911 and modify it to fit another high priced fan that also is not OEM. My approach, the new blower motor cost $25...

Advance Auto parts # 3910954
Factory Aire is the manufacturer and their part # is 35333
Designed to fit 90-2005 Chevrolet trucks.

I hope this information is useful to others.

Pics in my reply below

[mlfox]

Thanks for the tech tip. Would it be possible to post some photos?

Regards,
mlfox

[mkc1962]

MLFOX

Ive been working a long week and just have not had time to take any pictures. As stated I did not take the time to take any during the design stage. But I can take some of how it appears in the car now. I'll see what I can do tonight or the next day or two.

[enjefriy]

Ur mod sounds less evasive compared to mine. Atleast urs still resides in the smugglers box. I opted for a larger generic evaporate box installed immediately forward of the dash. So mine is way uglier of a solution than yours. Nevertheless I doubt any other 911 sc is as cold as mine thou

[mkc1962]

enjefriy

I thought of such an idea as well. And no doubt probably much more cooling efficiency. But I really wanted to stay as close to original location as possible, and keep it as simple and cheap as possible. That and, cooling efficiency was not my problem, it was lack of air flow due to a bad blower. At 100 deg central alabama weather, even when my old fan was on its last leg, mine was maintaining about 40 deg at the vent, which was plenty good for me. But it started making the growl of death, and rather than catch the thing on fire I decided to do what I did. During the first test run with the new fan, 98 deg outside,fan on high of course due to the poor design of the fan controller,for the first time since owning the car, I actually had to reduce the thermostat 1/2 way down after about 10 minutes.

[Peter Seow]

Yes the last owner of my did that. That blower is gone as well. same trick ten years ago

[mkc1962]

Ok...here are a few shots of the work

[khamul02]

With this in mind there are probably a dozen or so motors out there in US cars that would fit without modification to the smugglers box lid.

[wwest]

Originally Posted by mkc1962

Like so many others here, that chose to keep the AC in their cars, I finally had to make a move on that noisy Very Expensive Evaporator blower. However, like so many I just could not stomach the price of that cheap looking little OEM motor. I’ve heard of the better types by Griffith? (I think it is) but then on a 87 3.2 you have that problem of having to find another evap box lid due to the size of the motor. And still you spend some pretty hefty coin. To the purists out there, please pardon me if what I am about to share offends you.

Ive been working on and restoring vintage cars for near all my adult life. And many times have had to re-engineer things to make them work better or work at all due to lack of replacment parts. Not to say that I don’t myself keep things pure when I can. But sometimes, things like this pesky blower just don’t make sense.

My thoughts/goals for my blower replacement were.
1.) For it to be VERY inexpensive and easily obtained anywhere.
2.) For it to be done with keeping the smuggler box area as close as possible to original.
3.) For it to be easily removed if and when it be needed. Meaning no Evap box removal.

I also own a mint condition 73 GMC 4x4. To keep this short, coincidentally its heater blower FAN is an exact match size wise for the OEM Porsche unit. The motor is just a tad taller. To be exact the unit I purchased is for a 90-2005 Chevy truck.( I found it to be a bit shorter than the 73)

In our P cars the blower mounts from the bottom up. The Chevy unit drops in from the top/outside. Meaning no box removal if ever needing to replace.

1.) Remove your evaporator box lid. Remove plastic plate/fan cover and fan/motor itself. Toss motor fan in nearest trashcan or use as a paperweight.

2.) Using a dremel or similar and carve out lid of evap box to accommodate the new fan blade for drop in type feature. Use original motor hole as a pattern by which to center your new hole into the overall housing. Don’t get the hole any larger than you have to in order to pass the fan in, as what is left of the lid is what holds the fan in. And you will at best have about 1/2" plus all around.

3.) Place fan into hole and mark mounting holes around perimeter. Make or obtain speaker type mounting clips to go over each mounting hole on the lid of the box and install the Blower using short sheet metal screws. You might also want to make a gasket of sorts to seal around the blower to avoid loosing any of the precious cold air.

4.) You will need to make up a short (2-3") brown (to keep the German ground color code correct) 14guage jumper wire with a ring connector on one end, and a female spade connector on the other. Place ring connector under one of your mounting screws to provide a neg ground for your new motor. Then plug your OEM blower harness's brown into this ground jumper and the remaing red wire onto the provided spade plug that is built into the new blower.

5.) on the inside of the evap box you have a plate that goes on top of the fan itself. I myself used 1/8" lexan to shim this entire plate about 1/8" father away from the fan blade. even the original was a very extreme close fit. And even my original plate and fan had done some rubbing on my plate. I Then used Thumb gum (HVAC clay type sealant) to seal entire perimeter of this plate. Caulk would work, but would be messy.

6.) Reinstall Evap box lid.

7.) I mentioned above that this motor is slightly taller than the OEM. Roughly 1/8"-3/16". I took a piece of carbon paper and placed it on top of my motor then shut the smuggler box lid and bumped it a few time to find out where if any adjustment was needed. The carbon paper will leave black marks on the box lid.Remove the smuggler box lid.

8.) Soft towel, pile of sand or sand bag, and round end of a ball peen hammer would work best. Front yard grassy spot would work too. Place the towel down, Lid upside down into towel, using round end of ball peen, re-dent the lid to make things fit. Keep doing this until you get a clearance fit and can close the lid without it hitting the motor.

9.) Reinstall lid, and once again enjoy cold air. I’ve had mine in now for about two weeks. Blows equal to or better than OEM. Now I just need to do something about those pesky useless low and mid speeds.
Main thing is I met my goals and got the system working again for pennies. First time about 2 hours. Could probably do the next in about 45 minutes.

The tools for this, any DIY should already have. The evaporator box lid is your own that you will modify. No need to buy one from an older 911 and modify it to fit another high priced fan that also is not OEM. My approach, the new blower motor cost $25...

Advance Auto parts # 3910954
Factory Aire is the manufacturer and their part # is 35333
Designed to fit 90-2005 Chevrolet trucks.

I hope this information is useful to others.

Pics in my reply below

How did you determine if the motor/fan was turning in the proper direction for the Porsche squirrel cage blower housing?? And even more to the point even if you reversed the motor voltage polarity, assuming permanent maget "Field windings", was the curvature direction of the new squirrel cage blower/fan blades correct for the new rotation direction...?

Squirrel cage blowers will still "sorta" work being turned backwards and also if the blade curvature is backwards to the direction of rotation, but not nearly as efficient as otherwise and with lots of accompanying NOISE.

[mkc1962]

khamul02
You are probably absolutely correct....but I havent seen anyone spend days in a junk yard or parts house to find out. All Ive seen is tons of posts talking about what they cant find..I had no idea My GMC unit was even close until I removed it from my truck along side the OEM unit for comparison. I did find that the 90-05 blower for same application was in fact 1/8" shorter than the one that came out of my 73. That is why I bought it. I did spend about a hour going over every blower avail in my local Advance. Though many had motors that were shorter, none came close on the fan blade specs. As for a different dent on my lid, I consider that a much more tolerable adjustment vs some of the cut up and butcher jobs Ive read about. Once the carpet covers it you never see it. Not one bit more noticeable than the OEM Dent. NOW, I will admit I got a bit carried away with mine and probably re-dented it much more than I needed to be.


wwest
Luckily, my old OEM was still operational. I was able to compare rotation on both, and both the OEM and the chevy units were identical. No reversal of anything was needed. This was another feature that I could not find on any others in the above search of dozens. The fan blade size diameter and depth were also identical. The only noticeable diffrence was the OEM had many more individual blades on its fan
I also went as far to compare Field winding readings and both were within 80 ohms of one another, not enough to worry about. As my OEM had obviously gotten hot a time or two due to about being wore out, it is highly possible that could have vaired that ones reading. As for both motors, BOTH are designed to be varied via a bank of wound wire resistors. Or as many have chosen to do a DC Variable motor controller. The GMC resistor bank is much more user freindly than teh OEM unit that so many complain as low and mid basically useless. I think my first attempt at better control is to pull the bank out of my old GMC and just see how much better it controls in the porsche vs the OEM. If it handles it the same way it does in the truck, which is pretty darn good, I probably will buy a new GMC unit which goes for around $15 vs the pricey DC variable approach.

[steely]

This is great Mike - this problem has been the key to my not pursuing a repair of my AC. You may have inspired me, if I can get past peening the box lid, but it does offer a researched and tested solution.

[Boxer Boy]

AUGH! I should have read this thread before ordering the blower fan and motor! $25 bucks vs $194 (shipped) is no contest.

[mkc1962]

Dan,

Trust me you have to hit it pretty hard just to make some decent dents...use my sand/soft soil approach and you cant go wrong....might I suggest find a scrap piece of sheet metal and get comfortable first to make yourself feel better....folks been shaping metal this way for centuries.

[yogi]

I know this thread is a few years old, but I'm now in need of a new evaporator motor. The reason I'm not looking to go with the kuehl hurricane is my car is an 87 and I would have to look at getting an older evaporator box and cage. Which are not that easy to find and will add a lot to the cost of this job. I just wan to make sure I understand this thread before I start. My main question is It looks like I don't need to remove the evaporator to this. Is this correct? I'm just going in through the existing evaporator box and cutting the top to fit the replacement motor and cage. Buy Factory Air Blower Motor 35333 at Advance Auto Parts

It looks to me if I do screw up my option is to just go with the kuehl hurricane motor and a pre 86 evaporator box and cage, which I'm trying not to do. Does anyone see something different than what I'm reading in doing this replacement? Thanks,

[JAR0023]

There are two brackets(easy) bolted to the evap box top and four clips(hard) on the sides holding the top to the bottom. If you feel comfortable pulling these then yes you can removed the top while keeping the evap in place and not have to break the seal on the system.

The clips have holes in them. Use a piece of thin gauge wire or monofilament through the hole to keep you from losing the clips down into the bottom of the smuggler's box.

Keep in mind that the pre 86 and post 85 evap box lids aren't quite the same dimensionally. Pre 86 is taller and flat. Post 85 top the top of the box runs at a slight angle and is not quite as tall. The fan listed above may be a tight squeeze in your post 85 lid. I don't know, just thinking out loud. -J

[Discseven]

Mike,

The motor/blower install looks well done. Peening out the smuggler's lid... ballsy! Bravo on doing what needs to be done so to say! More applause on the economics!

40 degree vent temp is nothing to complain about... But the "growl of death"... LMFAO... that surly deserves attention.

Having struggled --- and still doing so --- with my AC temps... would appreciate a general description of your AC setup.

[NathanR]

What a coincidence. I too own a 87 911 and a 73 GMC pickup...can't wait to try this at home. Good work Mike!

[jimthe1st]

That motor/blower looks exactly like the one in my Ford PU. But I seem to remember that it uses a hose through the motor rear/side to get cooling airflow into the motor.

[yogi]

I have to say I'm quite impressed and have to thank Mike for coming up with this retrofit. Hopefully the original poster reads this and corrects anything that I say by mistake. I had to have an A/C specialist shop help do this. My original 1987 blower motor was seized.

Plan on more like 3 hours than the 2 hours Mike said. Since doing it the shop is assuming Mike did not do this all in one shot but either pieced it out during the day or even two days to come up with the different things that work. The clips that he mentions are called u-clips. The shop used washers to shim the fan instead of the lexan he mentions. They also had to replace the evaporator tube and the evaporator hose when doing the job. Both were crumbling and falling apart. They did use the thumb gum and also made a foam gasket where the motor now sits on the evaporator box. They turned it around from Mike's picture and have the electric hook towards the windshield instead of towards the bumper. This changes nothing on how it works, but cosmetically looks more correct since the motor doesn't overlap the evaporator box now. With the carpet from the trunk installed you don't even notice the bump you put in the smuggler's box lid. This will probably work on a pre 86 just like it works on the 86 to 89.

It definitely blows stronger on the high setting than it did before. On the medium setting it blows a little less than it use to on the old high setting. The low speed setting is still useless. Thanks again for this idea.

[mkc1962]

Original poster here. Thanks for all the positive feedback guys. I might add that was some 3 summers ago I did this and it still is working great.

Yogi,
No you do not need to remove the evaporator to do this. If memory serves me I did remove the lid and maybe I explained that in my original post. Sounds like you got it going though. Yes you are correct I had to design this over a few days, But If I had to do it again, I could do it in the time I mentioned. As for those u clips. I actually broke one or two and now have tie wraps holding those spots together. The mount ears are easily drilled and tie wraps easily installed and removed. You may want to try my blower resistor mod I mention below.

diskseven,

As for my setup...well other than the blower mod it is all still stock. I really need to upgrade to barrier type hoses, but as I add just a bit of freon each year to keep it going strong, I havent taken the initiative to go the next step. I will add that after some prior to the blower work I had to pull the system completely down to replace the compressor shaft seal. When I recharged I used the envirosafe refrigerant. Ive been using the ES refrigerant now for several years in several older vehicles and am very pleased with it. Head pressures run lower and temps are cooler. When I say I run 40 at the vent that is with my temp knob down at about the 2nd-3rd mark and my fan blowing mid to low.

I might also add. That after I did this fan mod, I also modded a spare blower resistor pack I had. As I am sure we all know high is ok but the mid and low are useless. I realized that each of those coils (resistors) was a certain resistance value based on its length in windings. The coils for low and mid were very close in resistance with a big jump from there to high. I removed the resistors for the low and mid speed (which are basically like giant springs) and clipped off winds until I got a values that more directly reflected a 3 speed range. I now have a true low mid high speed difference on my fan. Not to include this GMC fan blows lots harder than the high $ pcar oem.

Jimthe1st,

your not far off my friend. At the time I also owned a ford Explorer. However the ford fan blad wouldnt quite fit and the motor stuck out farther.

Thanks again guys for all the great feedback and happy to see that the info is being used by others. I know I may have offended a few purists out there, but I'll spend my saved $ on good bourbon instaed of overpriced poorly engineered parts.