Just Did The Honda Blower Motor Swap

[rossiz]

after reading a few posts on this (most recently the great write-up by hardway) i decided to go for it. my fan has been making some pretty horrible noises - whining, screeching etc. and the output was weak. picked up a honda fan assembly for $30 on fleabay, gave it a quick clean and got myself geared up for the job. 

 

i won't go into all the details, as this has been posted before, but i will whole-heartedly validate the improvement. the new fan is quiet and blows like crazy. couldn't believe how much more efficient it is at moving air. the design is basically the same, but the honda fan has a lot more vanes, which are smaller and it's a slightly larger diameter - about 1/4". this meant i had to open up the hole 1/8" all around, but that was pretty easy: just scribed the circle around the new fan, put the housing gently in the vice and went at it with an angle grinder, then cleaned it up w/a file. done in 15 min.

 

the new fan fit perfectly - had it's own nice rubber gasket and the holes lined right up. i made some additional rubber isolator washers for the mounting bolts and used the large washers from the z. the honda fan comes with a little vent tube, which i believe cools the motor by pulling in a little air through the windings. i used a paddle bit to drill an 11/16" hole in the z housing and the hose plugged right in. the plug on my honda motor happened to be the same 2 wire T plug as the z, but i made a little jumper/extension to give me a little more room for the wires. the honda motor can run either way, so i tested the polarity, then clicked it all together.

 

the biggest pita of the whole thing was getting the assembly out from under the dash, then putting it back in. holy crackers - what a miserable job. it would have been easier with the glove box or dash out, but i'm stubborn and was determined to win. and i did. while i was in there, i replaced the foam gaskets between the plenum and the fan and put a hose clamp on the vent hose that runs horizontally in front of the fan - this hose was continually falling off, not anymore.

 

anyway, it was a successful adventure and now i hope to be able to keep my windshield from fogging up every time it rains!

[gwri8]

I'm considering doing this and have been reading some of the threads.  Which Honda fan motor did you use?

 

Greg

[rossiz]

ebay seller advertised as for 88-91 prelude.

works like a champ.

[gwri8]

Thanks for the info.  I read about civic and accord blowers and now Preludes.   I'm actually looking a doing the heater valve and the blower motor is right there, so I might as well make a party out of it right?  But literally diving in head first into that cramped, dark, void of the floor is making me a little hesitant.  It seems that I'm not as agile as I used to be. 

[pbarcher]

I did this swap a few years ago and have this advice:

 

1) Disassemble the motor and clean the inside.  Mine was full of dirt, grease and metal particles.

 

2) Make sure that your ducts have tight connections.  I used black duct tape to seal the connections.

 

Even after doing this, I really didn't get much of an increase in airflow. Perhaps my motor was worn, so I'd appreciate comments from others who've made this swap.

 

Peter

[Namerow]

I did this swap for my '70 Z last year, using the blower motor and impeller from a Civic.  While bench-testing the unit with the newly-installed Honda parts, I discovered that the output performance (CFM) of the Honda impeller is extremely sensitive to direction of rotation.  Perhaps you have your motor wired so that it's running the impeller in the low-output direction?

 

FWIW, I tried the same test with the old Nissan motor and impeller and found that the OE set-up provided about the same CFM output (modest) in either direction!  This suggests to me that the Z's impeller is poorly designed and performs more like a paddle wheel than a centrifugal fan.

[Captain Obvious]

I don't have a need (yet) to do anything with my blower as it thankfully still works just fine. I know that could change in a moments notice however, so I've kept an eye on the concept of the Honda blower motor conversion.

 

But since you mentioned impeller design... One thing I've always wondered about is people say the Honda blower moves more air, but WHY does it move more air? Is it simply consuming more energy and spinning faster for a given selector switch position, or is it a more efficient impeller design that moves more air at the same speed? Is it a more efficient motor design that spins faster for the same amount of current?

 

I don't understand why people even care if it moves more air, Were all you guys who have done this conversion running their OEM blowers on the highest speed all the time and STILL wishing they had more airflow? Because if you're wishing you had more air and you're NOT running on the highest speed, then just move the lever to a higher speed. Or was it simply that the motors are failing and this is the cheapest and easiest replacement for NLA parts?

 

I assume nobody has measured current draw have they?

[SteveJ]

Noise and air flow are somewhat proportional on squirrel cage fans. Plus there is the wear and tear of 40 years of use on the stock fans. Those both could contribute to the difference in airflow.

 

Frankly with driving a car without AC in Georgia or Texas, the more airflow you can get, the better off you are.

 

I think some conversions on the 240Z have mentioned current flow, though I don't recall seeing any quantitative measurements.

[rossiz]

for me there were a couple of issues that made me decide to do the conversion:

1. on the highest setting the fan made a lot of air noise but very little air flow - severe fogging of the glass is a problem as its my dd and it does rain in seattle from time to time.

2. the motor was clearly in trouble, as it would screech and howl intermittently, loud enough to drown out the radio.

i haven't actually driven the car yet with the new fan (still getting the head replacement finished) but i'm hoping it makes a difference.

when i compared the two impeller designs i noticed 3 things:

1. the honda fan is larger in diameter, so the blades are traveling faster at the same motor rpm. since the blower housing remains the same size, the blades are closer to the side walls of the housing. maybe this has an effect on the amount of air that is engaged, reducing turbulence/inefficiency at the outside of the blade area?

2. the blades are smaller, and there are more of them, maybe a more efficient design?

3. the oem motor mount is set on spacers that put the impeller 1/2" farther away from the back of the blower housing. the honda fan doesn't use those, so the impeller pushes right up close to the back wall of the blower housing. perhaps this engages more air and/or reduces leakage around the impeller?

i have no training in airflow design, so this is all just my conjecture... all i can say is the honda blower is much quieter and moves more air.

[Captain Obvious]

Thanks for the concrete input guys. This change is on my wish list for upgrades and I appreciate the input.

 

I currently don't use my blower much at all. I suspect however, that if I had A/C (which I currently don't) I'd use it a lot more.

[S30Driver]

Any update on your blower swap's performance & its impact on the window fogging issue?

 

I am considering this swap as well to make my AC more efficient.

[rossiz]

well, i have a whopping 110 miles on the car now that the head is back on, and the defroster definitely works better. the airflow up over my head is enough to actually clear the rear hatch glass. don't get too excited - this ain't no cure for my electric defroster elements not working, because it takes about 10 minutes of driving after the engine is good and warm for it to clear the hatch glass, and thats of fog, not frost... BUT, the oem motor would never even dent the fog on the hatch no matter how long i drove. so it's a good thing.

 

the motor is a bit quieter too, which is a plus - although mine was pretty worn out, so ymmv...