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1962 Eldorado: Resistor for Heater/AC Blower

Started by Gary Christensen CLC # 21112, September 27, 2011, 12:17:16 PM

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Gary Christensen CLC # 21112

There is a unit that screws into the back side of the blower assembly on my 1962 Eldorado, to which wiring connectors attach.  After removing the two screws that hold it on, I see that there are "coil-like" things on the backside of the unit, through which the current flows from the connectors on the front side.  I believe that this unit must be the "resistor" that's shown on the wiring diagram in the service manual.  I'm also guessing that the resistor has something to do with the fan speed.

Can anyone explain to me how this unit works?  The one that is on my car has an extra connector (beyond what the wiring diagram in the service manual shows), so I know it's not the original one.  There has been some creative rewiring under the hood to accommodate the extra connector.

The "High" speed on the AC fan doesn't work.  The first three speeds work fine.  So I'm triying to figure out how things work in order to correct the problem (and because I want to understand how it works!).

The manual doesn't say what the "resistor" is or does, just that it's part of the circuit.

I also know my blower unit isn't original since the wire integrated into the motor is brown not green.  So that may be part of the mix.

Can anyone explain to me how this works?

Thanks!

Gary

quadfins

#1
Hi Gary,
   The coil IS the resistor. Think of it as a multiple heating element, like in your toaster. Electricity is pushed through a given coil. As the electricity works to push its way through, it loses some of its energy as heat. The electricity that makes it through is somewhat weakend, and therefore can't turn the fan motor as hard or fast. Each one has a different coefficient of resistance, so the more resistance, the slower the fan speed. That's also why they are inside the heater box - the air moving past cools them off. The fan speeds on the switch simply route the power through one or another of the coils, depending on how much resistance, therefore how slow the fan speed, you desire. Your wiper switch works exacly the same way.
   I'll have to look at the diagram again, but IIRC, when you slect "de-ice", the power may go through that single special coil - remember that de-ice also turns the fan on high speed.
  Give me a little time to look at the diagram again. Send a pic of yours, and I can do the same, so you can compare. These things are in every junkyard Cad, so if you need a replacement, they should be available. You have AC, don't you.
   Gotta rush off to meet the school bus - more later.

   Jim
Jim Eccleston
1961 Coupe de Ville
BATILAC
Senior Crown
DeCou Driving Award x 4

bcroe

Those resistors likely use the same wire as in electric heaters, and only survive
because of the air blowing over them.  Often the steel contacts they connect to
corrode from the heat, and you loose a connection.  There are lots of (different)
ones around, looks like somebody improvised after the original failed.  Bruce Roe

62droptop

usually when a resistor faily you loose all but high speed as high speed should not have any resistor
it sounds more likely thet your switch or connection is the issue

does the blower work on all speeds on the heat side?

Gary Christensen CLC # 21112

Thanks guys.  You've confirmed what I thought.

One of the things that confounded me was why the unit is in the blower.  Jim's explanation makes perfect sense.

The fan speeds on the defroster (which is a 3 speed switch) work, but I didn't remember that de-ice makes the fouth speed happen.  I'll have to check that out.  The AC does, low, medium, higher, but not highest.

Like I mentioned previously, my unit has an extra connection: one for the multi-connector, and two single connectors.  Only one is attached to the blower.  The wiring diagram doesn't show this, so I'm thinking it's not the right one.

I'm in Charleston, SC for the week and will take a pic when I get back to CT.  I wish my Cadillac were here -- I'd rather be working on it than going to the beach!

Gary

quadfins

I checked the wiring diagram to clarify. Low, medium and high on heater mode correspond to low, medium low, and medium high on AC mode. Super High is only with AC, when power goes directly to the motor - no resistor. De-ice turns on Heater High (not AC Super High), regardless of what position the fan speed switch is at.

Sounds like you are right - a replacement has been cadged in there. But correct ones are available.

Jim
Jim Eccleston
1961 Coupe de Ville
BATILAC
Senior Crown
DeCou Driving Award x 4