fan speed operation

[Turbofiat124]

When I bought my 1980 Spider in 1992, the fan only works on high speed. When switched to low speed, the fan doesn't blow at all. My first thought was the switch was bad so I replaced it. The low speed still does not work. So I'm assuming the problem is in the fan.

To the best of my knowledge, unlike the wiper motor which is a 2 speed motor, the blower fan uses a single speed motor and to slow the speed down they added a resistor to drop the voltage. So in one position, the fan get's full power, when switched to other position, power goes through a resistor.

So I'm thinking the resistor burned out in the early years of the car's life and in order to replace it, I'm going to have the pull the heater box which I would rather not fool with.

Is that how the system works?

I suppose an easier method would be to figure out what ohms this resistor is and add one at the switch and a jumper wire (if that makes sense).

[JerryH]

According to Brad's schematic, the motor does have a resistor in series for the slow speed. The red wire is the slow speed wire and the light blue/black wire is the high speed supply:

http://www.artigue.com/fiatcontent/Wiring_1978.pdf

[vandor]

AFAIK originally the resistor was built into the fan motor, as I have never seen an external resistor on a Spider. The new fans that are availavle now do need an external resistor.

[DieselSpider]

Mines the opposite as it only works on low because the previous owner disconnected the switch and dropped all the wires so that I could only fish out those for the common and low speed.

Yes since you have high you could put a resistor at the switch and tee it to the high speed wire as long as it doesn't get too hot in the confines of the center console.

[spider2081]

The heater fan motors are often make a high pitch noise from lack of lubrication but other wise are pretty reliable. I would check for a wiring problem before going much further. The switch should have a yellow/black wire feeding power to the switch. I believe that would be the middle contact on the switch. The lo speed wire is Red and the high speed wire is Lt blue/black. The wires from the fan are about 10 inches long (same colors) and connect the switch wires with single spade connectors inside those funny looking nylon insulators that sort of resemble fuse holders. I think if you lift the transmission wood panel that the shifter passes through you can access these connectors and check for power.

Have you tried connecting the switch wires directly together to see what happens. Yellow/black wire to red wire?? and then yellow /black wire to light blue/ black wire ??

[DieselSpider]

The heater fan motors are often make a high pitch noise from lack of lubrication but other wise are pretty reliable. I would check for a wiring problem before going much further. The switch should have a yellow/black wire feeding power to the switch. I believe that would be the middle contact on the switch. The lo speed wire is Red and the high speed wire is Lt blue/black. The wires from the fan are about 10 inches long (same colors) and connect the switch wires with single spade connectors inside those funny looking nylon insulators that sort of resemble fuse holders. I think if you lift the transmission wood panel that the shifter passes through you can access these connectors and check for power.

Have you tried connecting the switch wires directly together to see what happens. Yellow/black wire to red wire?? and then yellow /black wire to light blue/ black wire ??

The blue wire is what I have not been able to fish out. It may have been coiled up somewhere as its nowhere in sight. Its a FrankenSpider but at least the fan runs quietly (compared to the turbo diesel engine) on low and reliably. I need it more for defogging the windshield than anything else. We only get a few days a year here where you actually need the heater if you forget to put on a t-shirt or light sweater when braving out the extreme cold in the dead of winter.

[spider2081]

Here is a couple photos of wires at the heater box might help in locating them. They are on the driver side of the box probably visible through the radio opening in center console.

[RRoller123]

This might help?

Pete

[Turbofiat124]

I think years ago I pulled the switch and ran a jumper wire from the yellow/black wire to the low speed wire and it still did not work so I'm assuming the resistor inside the heater box is burned out. The only time I've ever had the heater box out of a Spider was when I stripped down an 81 model. Otherwise the one in my 80 model has never been out of the car.

Maybe I sound lazy but those boxes are not that easy to get out due to all the wiring in front of it. Even after I removed all the wiring that went to the power windows (which the car never came with) to make it easier to fit a modern radio.

So I really don't want to pull the box unless the fan just completely dies. I figured it might be easier to add a jumper wire and a resistor at the switch.

Actually I could just pop the clips off the side and pull the front cover off the box but it's still not easy.

On the other hand as long as you keep moving, you really don't need the fan. There is enough air forced against the windshield through the cowl at speeds above 30 mph.

I do have easy access to a Yugo blower motor in my storage building I can test the resistance to see what size resistor I need. Otherwise the heater box from my 81 model is in a barn loft and requires some work to get to my Spider parts stash.

[spider2081]

For what ever its worth I have had a few of the fans motors apart and don't recall ever seeing a "resistor" inside the motor. There is a winding of wire that is part of the brush block that could constitute some resistance and be represented in a schematic as a resistor symbol. I am more inclined to think the winding sets up magnetic field that counters the permanent magnets field. I have a note the fan draws 3.4 amps at 14 vdc on slow speed. So the resistor would need to be like 50 watts. That is physically too big a resistor to fit in the motor.

If there is a fan motor that is running on one speed and not the other the odds are there is a wiring problem between the fuse and the motor. It could be a broken wire in the motor but I doubt that because I would expect it to short to the motor case and blow the fuse.

Of course the car could have a non standard or aftermarket fan with one speed instead of the fan shipped from the factory. Only way to tell is to look around and see what you got.

[bradartigue]

I have to agree, though it shows on the diagrams it does not appear to be anything accessible.

[DieselSpider]

This might help?

Pete

Today I found the Blue Wire and the fan runs smoothly on high. Since the heater core is not hooked up I picked up a $9 electric window defroster from Harbor and it works just fine defogging the windshield on these Arctic Florida Winter days when combined with the blower motor.

Did get some scrutiny from a Sheriffs Deputy since there is a forward facing 1 1/2" red light on the electric window defroster however he did not pull me over for it. I suppose if it flashed he would have been more inclined to make an issue of it.