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Hi all,
I feel like a noob for asking this because I feel like I should be able to figure it out. I have read and re-read the owner's manual a dozen times.
How do you control the fan speed on a non-ac midyear? I am able to twist the fan **** to get the blower to kick on, but is the idea to continue twisting to adjust the fan speed? if so, my **** doesn't appear to want to twist any further than the initial 'on'. Any help would be appreciated!
Robb - Possibly something wrong with your fan switch. Starting with the **** in the 'Off' position, you'd rotate it clockwise to feel the first/second/third detents for Low/Medium/High speeds. The entire sweep from Off to High Speed is around 90-degrees of rotation. Are you noticing any of those detents at all?
And, when you say you can get the blower motor to turn on, does it sound like it's at top speed? The fan switch in my 66 Roadster has what I'd call 'light' detents and my guess is the switch is the original and has worn in a bit. The one in my 65 Roadster is much more pronounced and I think it's been replaced with a repro. Same function, just one is a bit smoother in operation.
Mike T - Prescott AZ
If you do have those detents present when operating the switch, there is a possibility that your resistor is NG. It's located on the heater plenum but facing forward so to remove it, you would have to work 'by feel'. There is one harness connector with three wires connected to it and then you remove the two sheetmetal screws and it pulls out. Again, you will be working blind and reaching up behind the plenum, basically in the gap between the middle of the plenum and the inside firewall. There are three coils to the resistor. If it's shot, you should see a burned up coil (or more). They are relatively easy to replace. Check out the pics of the resistor and the old heater plenum I removed from my 66 to see where it goes. The large opening to the left of the hole for the resistor is where the heater core sits.
Mike T - Prescott AZ
Hi Mike, I think that you are spot on with your assessment. After your initial post I took a second look at the switch, and I DO just barely feel the detents. The **** does rotate a full 90 degrees, but the fan doesn't turn on until it's entirely rotated to the high speed so I think the resistor makes perfect sense.
Does this work become any easier if I remove the glove box? I have a blown speaker currently and I plan on swapping the replacement radio to something that looks better than something from 1990, so I do plan on removing a fair amount of parts at that time.
Robb - Sorry for the delay in getting back to you. We were out in SoCal at our Granddaughters Wedding and just got back an hour ago. For the speaker replacement, I take half the car apart...just kidding,,,sorta. The glovebox comes out as do the radio side panels and the clock. For the heater blower motor resistor...none of those have to be touched. That's good news. Check out the pic I just took of my 66, same heater configuration for all 'non-AC' midyears. The Phillips screwdriver is my pointer in this instance. It's pointing up to where the resistor is located. When the inside heater plenum is attached to the firewall, that plenum extends out from the firewall and turns to the middle of the car. It's also a few inches away from the firewall and that's where you'll reach up (blindly, unfortunately but you can use a swiveling mirror to see it) and you'll feel a harness connector with three wires. Now refer back to the pic I posted earlier of the plenum and see the rectangular hole? There are two sheetmetal screws attaching that resistor to the plenum, one up, one down. Takes a 5/16 socket if I remember correctly. Once you have the connector off...then remove the screws and the resistor will fall out in your hands. Again, you will be doing this blind and 'by feel' but it's really easy. That resistor I used for my pic is from a later Vette but the Ohm resistance readings are the same as the midyears. If you only have top speed in your blower motor, I'm betting those two coils (for low and middle speeds on the blower motor) are burned up. If not, it still maybe a problem with your switch. Keep us posted on your progress.
Mike T - Prescott AZ
Got it, thanks Mike! The lower screw was bit of a pain to get started, but they both ended up coming out in the end. Unfortunately when I detached the existing resistor from the switch harness it fell directly into the abyss that is the plenum. I was able to get the new resistor installed, but unfortunately I still only have high speed. I suppose the next step is to test the switch itself. Does anyone know which of the terminals on the plug is low vs med? What voltages should I be expecting from each setting? I am assuming that the single flat terminal is the resisted output back to the motor, is this correct?
Hey Rob - Been a while since i messed with the blower motor switch and can't recall the blade configuration but always thought that the resistor was the way the power was controlled to produce '3' speeds, not the switch. Are you able to reach in behind the switch to verify the leads are hooked up properly? If they are, it's looking like the switch itself is the culprit.
Mike T - Prescott AZ
09-29-2021, 07:10 PM
65 non-ac vert - fan speed question
Unfortunately when I detached the existing resistor from the switch harness it fell directly into the abyss that is the plenum. I was able to get the new resistor installed, but unfortunately I still only have high speed. I suppose the next step is to test the switch itself. Does anyone know which of the terminals on the plug is low vs med? What voltages should I be expecting from each setting? I am assuming that the single flat terminal is the resisted output back to the motor, is this correct?