Talk Morgan Forums Morgan Sports Cars Maintenance & Servicing Loss of heater fan speed

If I understood correctly Leroy you simply substituted the fan motor which worked with a light bulb that also worked. Entirely to be expected. Given you only have two connections from the loom at the moment, if you can identify on the switch that slow was selected then it must be the same slow speed on fan motor.

I emphasise again you must have the three wires from loom connecting to three wires on motor to get both speeds assuming the problem is not at the PCB/switch.

As an interim test you could bare red motor wire and touch onto green/slate bullet connector on loom, with black to black connected to hopefully hear fan running at alternate speed. Make sure orange wire taped out of the way whilst doing this.

There is something strange here about the disconnection of the bullet connectors and bridging with a bulb. It looks as if the bulb was placed in series with G/S and O. If that were true and black was disconnected, the bulb would not light as there is no circuit. Am I reading it wrong?

Just to add weight to Deejay's comments Leroy, putting a bulb in series with the positive leg to motor, green/slate and orange or the negative leg, black and black will have the same effect as equal currents flow through both. The bulb will light at less than full intensity and motor may run slowly but likely not. It proves nothing since you know already the motor runs, at one speed at least.

Using a bulb is an inelegant way of testing and can lead to false conclusions. Use a voltmeter, maybe borrow one short term.

Everything you have found so far leads me to believe it's the fast speed you are lacking. The disconnected red motor wire adds to this conclusion. Try dabbing it on green/slate wire with orange disconnected to confirm motor runs faster.

Whilst I'm typing it's worth checking for the missing green/yellow wire from PCB. You have confirmed it has the full compliment of relays so should provide two speeds on two separate wires to motor.

More of an update. So Ive definitely got two speeds. I swapped the connections around orange to black and black to green slate and got the slow speed. I connected up the red wire to the green/slate and got the slow speed. So it's an absolute mystery why I got the slow speed previously, but there's no green yellow wire. I'll do as you say, and hunt for this wire. Hopefully I'll find it, and try to splice a wire on, and join it to the red, then all will be good. An easier explanation would be I'm mistaken about hearing the slow speed previously, but I'm certain I did. 🤷‍♂️

I only separated the bullets one at a time. The purpose was to see if the wires were connected to the motor. If there was a break in the connection then the bulb wouldn't light up. It did on each occasion but the motor didn't blow.

If it's a series wound motor (likely) it won't make any difference reversing existing connections BUT you cannot leave it powered like that or you won't have the option of two speeds. The black motor wire MUST be the common one on speed change connected to battery negative and/or ground via black loom cable.

If the motor ran at a different speed this may be because the attached fan was running in reverse! Either way please do not be tempted to connect that way again.

Whilst on the subject of do's and don'ts please do not even consider connecting loom cables to red and orange. The results are unpredictable but it will likely blow the fuse and goodness knows what else.

Having said all that pleased you have the two speeds proven with red providing low and orange fast. I would have expected the opposite but it's academic and would only change the slow/fast sequence anyway.

Good luck tracing the green/yellow wire from PCB or the motor end. It should be in the same branch as existing two wires and which runs for 330mm from main/thicker part of loom near a grommet. Since two faults are unlikely, you have already proven to yourself the issue was at the motor end.

Great advice as always Richard.
I've dropped the dash as couldn't properly look at the wires, and neither of the blocks coming out of the back of the PCB have green/slate or green/yellow wires 🤷‍♂️
The other picture shows an unattached block behind the glove box area with a green slate wire. I'm thinking it's not worth the effort to get another fan speed. At least I know how to pock around the back of the dashboard should I need to in future.

Ok I understand Leroy. To some degree I'm working blind with the cable advice as although there are three different versions of chassis wiring loom in the 2006-2014 parts book which appear to cover Roadsters from earlier still, none show the PCB specifically. It's often the case with Morgan wiring schematics that you have to read between the lines

Your call but if you want to give it one more try I would look again at the two cables that presently connect to motor wires. There should be a third to match third wire on motor. It will/should be with the others and these three covered wires alone travel back 330mm before it entering main loom. If you find the third in this group irrespective of colour let me know.

I am very suspicious of that red wire. Cut short and not even a bullet connector on it. Why?
Either it has never been connected from new or someone has cut it away for some reason, unknown.
Worth looking for the third wire as a matter of interest but generally think it might be better and safer to live with it as it is.

Doug the two speeds are almost certainly achieved by selection of different field windings on motor with attendant connections. I agree it's a mystery, but only why there isn't a third loom wire to give alternate speed. Given this situation it makes sense that unused motor wire was isolated and insulated as when the other winding was energised a short to ground on this wire would likely blow the fan fuse at the least!

Leroy has proven the third connection works giving alternate speed as expected.