[sixtysix]

I'm getting ready to dismantle my dash on my 66 GTO again. What a Pain, but someones gotta do it. I am installing my reconditioned speedo that was done by the one and only, P. Serio., well while I am in the dash I have a couple of bugs to take care of. The first is the fan switch for the Heat and air. My other concern is the amount of air flow I am getting. Is there a stronger fan on the market? I am also going to check the duct connections. If anybody has had this situation please share your fixes.

TY in advance,
SixtySix

[dataway]

One thing to check real quick is ... does air blow more with AC or Heat? Is there a difference? If it blows more with AC than heat, then it's possible the heater core has collected too much dirt. If it blow more on Heat than AC then possible the AC evaporator core is clogged .... they tend to get moist and collect dust.

And a fan switch malfunction and of course prevent the blower from going on high sometimes.

[HWYSTR455]

Yes, cores get the fins blocked with muck over the years, cleaning them is the fix (helps knock down odors too). While you're at it, do the seals, make sure the doors operate smoothly, correctly, and completely for sealing. Check/replace the high resistor too, and check the fuse, if the housing is all boogered from current/heat, replace it, a poor current doesn't help the fan.

Electric motors get old, and just wear out, if it's original, replace it. Make sure the squirrel cage is clean, and is tight on the shaft, as well as doesn't make contact anywhere which would slow it down.

You can always use duct tape on all the connection points so more volume reaches the vents, but obviously, that's not OE.

Everything as a total makes the difference, each item makes an improvement. When you do them all, usually you don't need to go to a better/different blower and/or cage.

I've seen folks who have 'upgraded' their' blower motors, but it's trial and error getting one that fits and actually blows better. I've seen folks adapt different squirrel cages too, but usually requires at least some fab. A lot of the info provided is when folks also do all the above, so it's questionable how much of an improvement the actual motor/cage replacement makes.

I say go over it once before you start looking into modifications, most of the time when you fix the OE stuff it blows much better/good enough. You will never get it to blow like a Benz 550, if that's what you're looking for, the duct design and motors are just plain bigger.

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[HWYSTR455]

If you tear it down, I say replace the heater core. IMO the aluminum ones are fine, I see no disadvantage to them, have used both. See no advantage with the copper ones either, over the aluminum ones.

Spray9 marine/general cleaner works really good on the ducts and boxes, as well as the evap core, spray, soak, rinse basically.

I've never done a pre-68 A-body one, so not sure if the evap case splits or not. You can google for service manual stuff, sure it would be helpful.

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[sixtysix]

my problem is, the blower motor stays running on low speed. Could it be, that two speeds are trying to run at the same time, which in return slows the motor down at all speeds. I have my dash apart. How do I test the speed selector switch while it is disconnected and out on the bench?

[HWYSTR455]

I would have to look at the manual, but as I recall, there's no real 'off' for the fan, unless you turn the direction selector to 'OFF'. The low, med, and the med-high fan settings are on one circuit, and high is it's own circuit. High has a resistor somewhere, on 68-72, it's in the cowl.

On the 68-72s, the high blower circuit gets it's own sub harness too, with a relay.

If I had to guess, since regardless of what setting the blower switch is on, if it blows the same speed, something is hooked up wrong or shorted.

There's a troubleshooting flow chart for diagnosing blower motor circuit/function, see if that helps?

If you've never had it apart, chances are, it's time to go through the whole system. I know it sounds like a pain, but once you do it, it lasts for 10s of years.

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[aceaceca]

I have a 65 which I recently went completely through. Not 100% sure 66 is same but think it is. The blower air has to go past the evaporator coils before it gets to the heater coils. If the AC coils are plugged up the air flow to the heater will also be affected. After all these years you can bet the evaporator coils are messy with debris. Pine needles are the worst to get out and they like to catch other leaves.I did not have the fender off for access to the back side of the coils but I undertook creative efforts to clean them up. I vacuumed with a shop vac with a reduced diameter hose that i shoved down the blower plenum going to the evap coil. I then modified a toilet plunger to contain and blast hot water and soap from inside the cab through the coils. There is a drain on the other side of the evap obviously to let condensate out. I siliconed all the gaps on the inside plenums. I duct taped over the lower air outlets so that only the center and side outlets blow. I replaced the factory fuse coming off the alternator, this feeds the blower, with a huge 1/2 in blade type. Owned this car from new and always had trouble with frying the fuse or holder. Turns out there was a bulletin to put two 30 amp fuses on there. No more problems there now. Bottom line, it blows hard now. There is a post of mine here somewhere with details.