[roger1]

Originally Posted by dataway

... I'm going to try to test them in the housing with a wind speed meter and a manometer to see if I can determine which one "blows" more . I have an AC/Heat housing with the cores still installed, maybe I can measure which one moves more air.

I applaud you for doing this for us!

[dataway]

Well, I'll just start with the pertinent information. Both the PM136 and the original OEM blower (68 GTO) appear to perform almost exactly the same. Both registered almost the exact same 43 mph outlet air speed on my test setup.

Setup was not by any means perfect, but both motors were subject to the exact same conditions.

One takeaway I found was that any air leak in the AC/Heat casing has a considerable effect on the outlet volume. More so than I would have thought. Speciallly if it's in the area of the blower fan.

Pictures below show the power readings ( I built a new box to measure the draw that got consistent results) and the test setup I was using.

Would have liked to report better performance from the new motor/fan ... but my results didn't show that. However fan performance is very complicated, it's possible that the new fan would perform better with varying levels of discharge head (resistance) at varying fan speeds. Would take lab to figure that out.

I do think the new motor/fan is a bit more efficient, moving the same amount of air with less power consumption (first power reading is the PM136). A more realistic 13vdc supply might have changed the results too. I'll try it again tonight with a battery charger hooked up to the battery.

[roger1]

Charging voltage would be between 14 and 14.5V. If you can do that, it would be a better simulation. I'd also go with 12Ga wire for a low voltage drop to the motor.
Another suggestion I have is to put a tube in the front of the air intake to the fan Same diameter of the hole. It might make a difference. The way you have it, it might be causing turbulence at the intake. You might even try a smaller diameter tube. Restriction from size might be outweighed by getting laminar flow to the fan.

[dataway]

Definitely want to try it at a higher voltage. But I figured even with errors in the test setup design ... since both motor/fan combos were subject to the exact same conditions the results would still be valid. Not for testing the max output, but for comparing the output of one to the other.

I can see that air leaks, restrictions both upstream and downstream have a pretty major impact. So make sure AC and Heater coils are blown out well, nothing hanging off into the vent passages, no leaks at interior vent connections, blower intake tube and body intake cavities are clear etc.

[roger1]

Agree. Definitely valid and glad you are putting this effort in.
Another thing to try along with the increase in voltage is to restrict the output some to simulate the car's venting system to compare how each motor reacts to the load.

[dataway]

For the tests the entire output was restricted to about a 3" hole .... the last photo in post #62 showing the meter ... it's lying right over the top of the hole, made it the same size as the meter fan.

Actually these systems seem pretty well engineered, the fans produce more pressure than I would have guessed. Remember not to over do the sealant thickness between the housing and the firewall, the firewall provides the "back side" of the housing and if it's spaced too far out it allows too much clearance between the fan and the firewall, allowing air to recirculate ... kind of like clearancing a Pontiac water pump plate.

[dataway]

Did another test at 12.6 vdc, surprisingly no change in output. My guess is the system has an aerodynamic limit at which point no matter how fast you turn the fan it's not going to push any more air. I can say either the OEM fan or the PM136 moves PLENTY of air, if I had replaced the motor/fan and still didn't have adequate air at the vents I'd be looking for another cause. Control door in the wrong place, obstruction in the suction or vent passages. This system pulls air from the cowl area correct? Try to make sure there is no debri in there. Also ensure the fan speed resister is in proper condition and does not have debri on it causing it to overheat. Good grounds, all the usual suspects.

In my test setup ... I'd venture to say it was pushing enough air out of that one 3" hole to cool a car without problems, so assuming the fan motor is in good shape I think flow issues have another root cause.

[roger1]

In all the older cars I've had, I've always noticed a drop in air flow when I've accidentally killed the engine with the blower on high. Of course that's a pretty major percentage drop in voltage going from about 14.5V to about 12.6 at the battery. Accounting for voltage drop to the fan motor, the percentage is going to be worse. I'd estimate it goes down from 13V running to 11V when the engine dies. About a 15% difference.

I think you accomplished what you set out to do with your bench test. The new motor doesn't have the night and day difference that some have described. It stresses the point that it's important to not have leaks anywhere and that everything with the venting controls are operating just as they should.

[vertigto]

Good info.

Still think it makes sense to replace the 51 y/o blower motor in my car, now that it's all apart. I'll hang onto the OEM for future consideration.

[roger1]

I was doing a little searching and found something interesting:
https://www.chevelles.com/threads/mo...2#post-5714113

Then a fan that looks like this could be installed:

[dataway]

Yep, that would probably move more air.

Complicated system, probably a dozen things that could cause a drop in air flow. But yeah, to me ... replacing a 50 year old motor is a nobrainer. Could be older motors need that extra voltage cause they are 50 years old, old brushes, old bushings etc. The OEM motor I was testing came off a low mileage car and has been in storage for 30 years so it didn't see much use. Other people with a motor with lots of time on it might see a good increase with a new motor, could be the reason some are very happy with a new motor.

Wonder if high speed setting uses no resister spring at all, or if it's limited? Just thinking, if so, quick fix might be to just rewire to send full voltage to the motor. I was impressed with the volume of air moved .... but then I was using a direct connection to a battery, no resistors.

[roger1]

Only the lower speeds use a resistor. High speed voltage goes through a relay that gives full voltage. Upgrading wire to 12Ga or even 10Ga that goes directly from the relay to the battery and from the relay to the motor would lower the voltage drop and that would help some. This is also good to do with upgraded headlights and electric radiator fans. You definitely want a new relay too. Relays will get a higher resistance through the contact points over time and usage.

[dataway]

Yep, just checked the circuit diagram, high speed setting bypasses the resistor circuit. So the relay in question is the "Master Relay" which seems to provide power to everything including AC clutch circuit etc?

[roger1]

Originally Posted by dataway

Yep, just checked the circuit diagram, high speed setting bypasses the resistor circuit. So the relay in question is the "Master Relay" which seems to provide power to everything including AC clutch circuit etc?

The '69 service manual shows the that it is a dedicated power wire to the alternator. It has a 30A in-line fuse. It says the wire color is "BLK-DBL ORN".

[dataway]

Yep, that's the one.

[roger1]

I may investigate a little further on the idea of using the left (facing the firewall) half of a Grand Prix evaporator box. I like the idea of that larger fan. I may have to get to a point where I can mock things up to see if I think a GTO has the room to do that. I'm not there right now. Body is still not on the frame yet.

[ta6point6]

I found that changing to a cs130 alternator helped a lot especially at lower rpms. The stock alternator only puts out about half the amps stamped on alternator case at idle. So if you have AC on energizing the clutch, as well as stereo/amp going and fan motor running on high. The stock alternator is struggling to provide enough juice to vehicle especially at idle. The switch to a cs130 was a simple bolt in with a plug adapter for another 15, alternator about 100. The cs130 puts out more amps at low rpms and keep the fan motor buzzing along on high.

[roger1]

I have a CS130 in my '55 Bel Air and intended to buy one for my GTO too. Last week, I found a place online called Quick Start Alternator and gave them a call to order one. He said he sells them but said he doesn't like them at all and said they were GM's "junk" alternator. He talked me it to buying a hybrid that he builds using the best parts from 3 different alternators. It sounded like a great option and I ordered it. I received it today and just mounted it up.

https://alternatorparts.com/hybrid-cs130d-10si-series-alternator

I ordered the 105A version since that is plenty for what I need. I'm now wondering if I should change out the CS130 I have in my Bel Air for one of these.

[dataway]

Not sure about the GP part, but the A body case has a dish in the passage from the blower to evap to clear the wheel well I think. Seems like a "taller" case would need even more of a dish in it. Although it's a modification that probably wouldn't be too hard to make.

[roger1]

I think you might be correct that it would have to be altered to clear the inner fender. I'd like to have one to experiment with but I don't think I"m likely to find one. No sign of one on ebay past or present. I did find that a place called Franks had 3 of them but only sell it complete with entire outer shell and the inside box too. I don't want to pay their $275 just for an experiment. I'm not willing to put in the time traveling and searching wrecking yards either. Most wrecking yards don't keep cars this old anymore and this part is only on Grand Prix cars from '69-72.

So, I'm likely to get one of the van motor choices and use 10 ga wires for the ground and power feed and make sure relay doesn't add a voltage drop of any significance. My goal will be to see 14V at the motor with it running on high.

One thing I wonder about is why a noise suppressor was deemed necessary and used on these cars. I've heard these referred to as a capacitor but I'm pretty sure it's called a choke. I'm thinking that the new style motors with a permanent magnet don't need this. Plus, who uses AM radio anymore? I would guess it adds a voltage drop.