Blower motor air flow 92-97 vs 87-91

[junk]

I'm nerding on my a/c blower motor and how much air they put out through the vents. My 93 seems to put out way more air than the 89. Now both of them have new a/c evaporators and new ford blower motors. Also both of their a/c boxes have been recently cleaned. So where I'm going is they are both pretty comparable for checking vent air speeds.

I grabbed a little wind gage from work and used it to check my cars. My subaru which has great a/c IMO was 13mph on high. So below are the results from my 89 and 93 ford pickups. My end goal is to get the vent speed on my 89 up to my 93's vent speed. I really like my a/c and want it to work full out.

Results from 89 F350
Low - 7.7

You must be registered for see images attach

Med/Low - 8.2

You must be registered for see images attach

Med/High - 9.2

You must be registered for see images attach

High - 12.2

You must be registered for see images attach

 

[junk]

Results from my 93 F250. I have a junk 96 F150 onsite and it appears to match the 93 also.

low - 5.5

You must be registered for see images attach

med/low - 9.0

You must be registered for see images attach

med/high - 12.5

You must be registered for see images attach

high - 15.4

You must be registered for see images attach

So what would be the main differences between these? Is it just the dash and vent routings? Is it some wiring difference between them?

-Jeremy

 

[Andertusa]

Maybe the motors are different, operating at different speeds. I'd probably put my money on the squirrel cage being somewhat different, as I've had to replace a squirrel cage on my parent's Astro and the replacement steel unit seemed to blow differently than the old, cheap plastic one did.

 

[ifrythings]

If you can, to rule out wiring, do the test the same but put a multimeter on the blower motor itself and see what the difference is, just make sure you have as close as possible battery voltage between the two (make sure they are both running)

 

[junk]

andertusa, Ifrythings - You guys hit on the next two issues I'm wondering. I think the squirrel cage in my 89 is aftermarket and I think it might be metal. So I'll have to check that out. The 96 I have has a ford blower motor still so I bet it still has a ford squirrel cage. I'll swap that into my 89 and see what it does. (EDIT- just checked rock auto I definitely did order a metal squirrel cage)

Regarding the wiring that was my next thought also. I need to determine if they are getting the same voltage. I'm not sure I can probe the plugs on those while plugged into the fan. I'll have to check that out. I definitely want to check the voltage of them under load. Not just at the connector. I also thought I could maybe use my clamp on amp meter to check amps. If one's drastically higher I'll assume it could have more parasitic loss in the system.

I'll post my findings.
-Jeremy

 

[riotwarrior]

Minutia

 

[Andertusa]

andertusa, Ifrythings - You guys hit on the next two issues I'm wondering. I think the squirrel cage in my 89 is aftermarket and I think it might be metal. So I'll have to check that out. The 96 I have has a ford blower motor still so I bet it still has a ford squirrel cage. I'll swap that into my 89 and see what it does. (EDIT- just checked rock auto I definitely did order a metal squirrel cage)
-Jeremy

No problem, if I can pass along any of my limited knowledge that another might find useful, I'm glad to help.

 

[junk]

I played with this about 30 min tonight. And made a 17% improvement.

Swapping to a ford plastic squirrel cage vs the aftermarket metal brought vent speeds up to 13.3.

You must be registered for see images attach

When swapping the fan I noticed there was a ground wire I landed on the fender that was really long and came from the a/c box wiring harness. So I moved that ground to the cab where a ground bolt used to be above the heater/ac box. That got the vent speeds up to 14.3. So another big improvement for little effort.

You must be registered for see images attach

Overall I'm pleased with the 17% increase for no more effort than it took. I know it's probably nerdy, but I'm glad I used the wind speed meter. This way I had a way to measure the improvement vs just thinking it does better.

-Jeremy

You must be registered for see images attach

You must be registered for see images attach

 

[Andertusa]

A combination of both things, good to hear you've made an improvement you're happy with.

 

[laserjock]

Looking at your dash lights, I'm guessing you are doing the test with the key on engine off? I'd check your system voltage or go ahead and start the truck. Fan speed will depend on system voltage. If the system voltage is a tick higher on one than the other, that might be the rest of your difference.

Edit: wait sorry. I see the tach needle now. I may still be right but for the wrong reason though.

 

[junk]

Laser - I don't disagree that there's probably a voltage difference between the two. That's the next item I'm going to check is voltage between them. Since I had the 89 all blown apart and reinstalled everything having a missing ground is completely possible.

Yes both trucks were running at the time of the testing. Wanted to make sure they had full voltage. And I wanted to test the vents so I needed the vacuum to switch controls.

On another note in the 89 the volt meter is always low on the gauge, but I never have battery issues. So i'm planning to verify my 3G is working correctly. I'm wondering if it slips the belt at times. I need to do a system voltage check anyway.

-Jeremy