Correct electrical wiring of the heating blower (S1 3.8)

[paydase]

I am reconditioning my 3.8 FHC heater box assembly that does not work anymore and am wondering what should be the correct electrical wiring of the blower (positive ground).

Before dismantling it, I noticed that the electrical resistance under the blower had its two ends soldered to yellow-green wires, so maybe to the (positive) ground, which is odd because that would shunt the resistance and make it useless. But who knows, maybe these two yellow-green wires are not going to the same electrical pole or even to the ground, I will have to check.
There is another black wire that is probably connected to the negative in the electrical circuit.

After dismantling I noticed there are actually 4 wires coming out of the electrical motor box (instead of 2 in the picture shown by SNGB, see below.
Unfortunately it seems that the motor box cannot be opened (is it really the case or should I pry on the box to open it?).
As a consequence, I could not see the electrical connections inside the motor and I have to make guesses on how the circuit should be correctly wired. On the outside:
- two of the wires (red and black, here disconnected) make a loop (what for?...)
- an orange one (so probably also red) goes to one end of the resistance
- and another black one goes out into the main electrical circuit (probably the negative).
- not forgetting the two (currently unsoldered) yellow-green wires...

As said above, the electrical circuit shown on the picture of the blower from SNGB is completely different (please note that SNGB shows the same picture for the electrical motor of the negatively grounded S1 4.2 and the positively grounded S1 3.8, so that I better assume that red is positive and black is negative/ground):
- a black wiring to a screw inserted in the body of the motor (so probably to the ground)
- a second black wire connected to one end of the resistance and probably going out to the ground of the main circuit
- and a red wiring coming out of the motor, connected to the other end of the resistance and going out probably to the positive of the main circuit.

As I understand it, the resistance and the coils inside the motor should form an inductive oscillator (but I may be wrong...) so that one end of the resistance should be wired to one pole of the circuit and the other one to the other pole.
Plus the grounding of one of the ends of the resistance and/or of the box.

Because of its current infinite value, the resistance is shot and has to be replaced.

First question: does anybody know the correct value of this resistance?

Second question: without the possibility to check the circuit in the box, could you give me advice to make a correct wiring:
- could you confirm that each end of the resistance should be connected to one pole of the main electrical circuit?
- should one end of the resistance be connected to the ground?

[abowie]

Resistor is 3.4 Ohms

Best way to understand the wiring is to test the motor with a 12v power supply. The resistor acts to provide low speed.

The wiring diagram in the manual shows what colour wire to attach before and after the resistor.

[cactusman]

The motor you have removed with four wires does not appear to be an original 3.8 motor. The original fan motor has two wires and is single speed. Jaguar made it 'two speed' by having a three position switch. Position one is off. Position two feeds the motor via a resistance so the motor runs at less than 12 volts and is slow. Position three feeds the motor directly and is fast. There will be two wires at the bit of loom feeding the motor. One is green/yellow and connects to the red wire on the sngb part (which is correct as far as wires go). The other is green blue and goes to the wire that connects to the resistor only.

[paydase]

Thank you to both.
Very helpful.
I will make the tests and look at my car wiring.

[johnetype]

Agree it does not appear to be an original motor. I think you've either got a motor whose magnet exciter wires have been brought out separately (to allow it to be easily reversed) or more likely it is a 2 speed wiper motor in origin with three brushes inside, one offset so it will run at two different speeds. That way you wouldn't need the resistor for speed control explaining why your resistor is hanging in the breeze.

Suggested options:

Fit an ex Pontiac Fiero motor and fan - plenty of threads on here about this upgrade
Fit an ex MG motor and fan
Fit SNG's replacement motor
Reuse your current motor - assuming it works well enough to blow sufficient air - and you'll be able to wire it up back as it was without the resistor.The other three options all need a resistor for controlling the slow fan speed and can work with positive or negative earth.