Air Conditioning Fan Upgrade

[surfnturf]

As a new owner of a 1966 New Yorker, I am very happy with every aspect of this car with the exception of the AC fan/blower. I'm not sure if it is just normal or if the fan is just weak. My wife and I took it out for our Sunday drive last weekend with outside temps in the upper 90's. The AC blows very cold but the fan on max seems to be about the same as our modern cars on the medium setting. While it kept us plenty cool and seamed to do the job, I think it would be less than adequate to cool back seat passengers on a similar day. I have a 1968 Ford Bronco and as a common upgrade, many people put a late model chevy blower on the HVAC unit and it makes a huge difference in the CFM. I was just wondering if any of you know of such an upgrade for the Chrysler.

 

[live4theking]

I've actually been wondering about the same thing. While coming back from Carlisle me, the wife and the youngest were cool and comfy up front, but the three older kids in the back seat would've like a might more airflow.

One difference for sure is that the fan speed is controlled by resistance where as in modern cars the speed is controlled by switching the fan on and off. If there is a fan that would push more cfm that would be great. Even tough my fan blows, I've wondered if it's tired. I wish I had a known to be good one to test against.

Maybe it's the pitch of the blades on the squirrel cage?

Cage from a 68 NYer

Cage from a 96 Jeep

I'm interested to see if anyone has done some experimenting.

 

[CBODY67]

One thing to do first is to seal all of the slip joints in the hvac ducting. Either with some soft foam tape or a week-adhesive duct tape.

THEN, figure out how to aim the air to the back and still keep some up front. Using the center vents for the rear, with an angle to each side, just missing the rh and lh front seat passengers, but hitting the rear seat passengers more directly. Using the edge vents for the outside of the front seat passengers and the rear passengers, too.

A general side issue is just how un-insulated the cars back then really were, compared to more-current model years. Just enough jute above the headliner to keep the roof panel quiet. Similar under the carpet (which augments the factory undercoat). No heat/sound insulation in the doors, other than the door panels themselves (and related plastic water shields, as GM used PAPER water shields, typically). Unfortunately, upgrades in these areas require some disassembly and $$$ to do.

A different blower fan might be the trick, though. Have to make sure the vanes are pointed the same direction as the OEM fan, plus both fans have the same direction of rotation.

Just some thoughts,
CBODY67

 

[volksworld]

when i got my 68 fury the fuse box around the blower fuse was melted and at the time i jumped it out with one of those holders for a blade type fuse...i have no idea if that was because a previous fan had gone bad and drew too many amps or if the fuse contacts were corroded and that caused enough resistance to melt the box...a couple other parts harness/fuse boxes i've saved also have the blower fuse area melted so i assume this is a common problem...i'm currently replacing the box with one that isn't melted (after 20 yrs with the blade fuse but may still leave it hooked up)...this is part of trying to get the a/c to work so i'll be checking the resistance and current draw of everything and might even rig a relay in there

 

[Ross Wooldridge]

When the AC is set to MAX AIR, there is an "extra" full power switch that ups the fan speed. It is found on the passenger side of the AC box - a little arm moves up and flips a switch which is supposed to completely bypass the blower motor resistor and allow full fan operation. You can see it if you look from the passenger side door, kneeling on the ground. Have the car running and go from Max Air to Defrost to see the arm move and flip the switch.

It's called a Bypass Switch. The bend in the vacuum door arm flips the switch.

However, it may not be working. Also, as the fan switch and the circuits age, the fan doesn't blow as strongly.

I just went through this issue with my 66, and wound up wiring a direct feed to the blower motor from the accessory fuse in the fuse box (with a nice toggle switch designed for high amperage 12V applications, and an extra inline fuse for protection). Now the fan blows much more strongly, although I only have one speed.

 

[CBODY67]

In the 1970s, GM used the "high" fan speed to trigger a relay, bypassing the blower motor resistor gang, to use full battery voltage to the switch.

 

[surfnturf]

When the AC is set to MAX AIR, there is an "extra" full power switch that ups the fan speed. It is found on the passenger side of the AC box - a little arm moves up and flips a switch which is supposed to completely bypass the blower motor resistor and allow full fan operation. You can see it if you look from the passenger side door, kneeling on the ground. Have the car running and go from Max Air to Defrost to see the arm move and flip the switch.

It's called a Bypass Switch. The bend in the vacuum door arm flips the switch.

View attachment 608961
However, it may not be working. Also, as the fan switch and the circuits age, the fan doesn't blow as strongly.

I just went through this issue with my 66, and wound up wiring a direct feed to the blower motor from the accessory fuse in the fuse box (with a nice toggle switch designed for high amperage 12V applications, and an extra inline fuse for protection). Now the fan blows much more strongly, although I only have one speed.

Thanks for the advice, Ross! I believe the actuator is working as I can hear it activate but I get what you are saying about the aging circuit. I think I'll give a go at the direct feed wire to the blower and see if that kicks it up.

 

[live4theking]

My 66 doesn't have the by pass switch. I'll have to look at the wiring diagram some more.

 

[Ross Wooldridge]

My 66 doesn't have the by pass switch. I'll have to look at the wiring diagram some more.

Really? Is it underdash? The indash ones all had the same HVAC box...

 

[live4theking]

Really? Is it underdash? The indash ones all had the same HVAC box...

I rebuilt my box. There is no switch in that area. I'll try to remember to look at the FSM in the next few days.

 

[Clover]

It’s a common problem with old C-bodies. What I did was got a 30-amp relay with wiring and mounted it under the battery tray, then wired the +12v relay output directly to the fan input (at the fan), through a 30 amp diode. I wired the relay pick signal directly to the blower fan switch (removed the old wire for the high speed, from the connector and taped it off). Then grounded the relay, added the +12v feed to the relay, from the battery, and now have a much higher fan speed on “high” setting. If you want a separate switch instead, run the relay pick to the battery positive and the relay ground through the aux. switch, to ground.

 

[live4theking]

It’s a common problem with old C-bodies. What I did was got a 30-amp relay with wiring and mounted it under the battery tray, then wired the +12v relay output directly to the fan input (at the fan), through a 30 amp diode. I wired the relay pick signal directly to the blower fan switch (removed the old wire for the high speed, from the connector and taped it off). Then grounded the relay, added the +12v feed to the relay, from the battery, and now have a much higher fan speed on “high” setting. If you want a separate switch instead, run the relay pick to the battery positive and the relay ground through the aux. switch, to ground.

I'm usually good with following electrical, but would you mind making a sketch of what you did.

 

[Clover]

I'm usually good with following electrical, but would you mind making a sketch of what you did.

Here’s a wiring diagram:
Update: the diode is unnecessary. Thanks, D Cluley!

 

[D Cluley]

Here’s a wiring diagram:View attachment 610422

I see how this works, but am not sure why the diode is needed?

 

[Clover]

I see how this works, but am not sure why the diode is needed?

Lol, now that I look at the diagram, I see that the diode is not needed. When I first designed it in my head, I was thinking that it would trip the relay on lower fan switch selections but that is obviously not the case. I believe I overthought it!

 

[live4theking]

Where did the diagram disappear to?

 

[Ross Wooldridge]

I was wondering that too.

 

[Clover]

Where did the diagram disappear to?

Sorry! Guess I killed it when I updated, lol. Getting old sucks!