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

So yes it’s looking like the motor then if you have power on the slow speed out. If it was mine I think that I would isolate the motor and power the motor independently from a battery first to be 100% sure (but only if you are confident of the connections!). Just maybe there could be some weird current limiting going on with the pcb that I would check first before replacing/repairing the motor.

Yes basically that’s what I would do to test the fan motor. Completely unplug the unit. Rig up a separate ground and test the slow and fast speeds from a temporary supply. But…. Having said that please be aware that I know dangerously little about electrickery. The electrical experts here may disagree or suggest otherwise!

Bit of an update. I've located the motor, and it indeed under the bonnet untop of the bulkhead like John suggested. I removed the gauze filter and 3wires come from the motor but without taking things apart, I can't see where they join the motor. These wires are black, red and orange. Tracing these wires to the drivers side, I find the orange one connects to a green and slate wire and the black to a black wire. The wires come from the loom. The red wire doesn't connect to anything and was cut shorter than the black and orange wires and taped up. I've separated the bullet connectors and bridged them with a bulb, firstly the orange and green/slate. When ignition on and the blower started at the high speed setting, the bulb lit, but the blowers didn't work. The same for the black wire, and the bulb lit. All reassembled, and the high speed setting worked, but not the low on.

Does this mean that the problem lies with at the motor end? I've given the wires to the motor a jiggle and nothing happens when it's on the low setting, so might be able to rule out a loose wire, or maybe not.

I wonder if swapping the feeds around might be a better initial option, so the feed from the high speed goes to the wire the took the slow feed. That might discount a loose connection at the motor end. It may also change the order so that it goes from off, to slow, then fast. Still bizarre that the red wire from the motor isn't connected to anything. Guess that would be for a super fast speed 😂

Glad you have made some progress Leroy.

Three motor wires confirm its a two speed fan motor as expected, with each speed probably derived from differing internal windings.

There should be three wires from loom to connect to it via bullet connectors as mentioned earlier in thread though.

Can you confirm without doubt the fan did work on two speeds before the fault?

As things stand from your description above it can only work on one speed

FWIW and to reiterate the loom wires to motor should be:

Green/yellow 12v +ve to high speed connection on fan motor
Green/slate 12v +ve to low speed connection on fan motor
Black ground/-ve to matching connection on fan motor (logically black)

Note fast and slow green cables may be reversed - I got the colour coding for each speed from latest Roadster schematic.

With connections to motor broken a multimeter set to cover voltage is best way to check correct functioning of switching. With negative probe on black wire you should be able to see 12 volts on each of other loom wires corresponding to fast and slow selection on switch.

Just checked and the rape wrapped sour from the loom only contain two wires, the black and green/slate. Excuse my ignorance, but do looms carry negative/ground wires?

Thanks for posting the pic’s John. So it’s looking like there might be a single and dual speed board. With the second relay (next to the 12 pin connector) missing on the single speed configuration.

Leroy from your second picture it looks like if you were to take another pic maybe with a bit more light from the flash you might be able to just see if the relay is there or not? Or if you could lay on your back and poke around with a suitable bent plastic probe you might be able to feel if that second relay was in place? I believe some early Roadsters only had one speed....

Most certainly yes and almost invariably black, though they do terminate in an actual connection to ground/vehicle chassis at some point to complete circuit to battery. Its more common than not nowadays for cable provided ground connections to components where previously they may have relied on casing and attachment to metal body of vehicle to provide ground return.

There will almost certainly be a green/yellow wire as part of loom nearby somewhere. As Roger mentions please be careful with loose connections and test as I suggested.

Hopefully you will appreciate that the third motor wire cut short and taped off is not as it should be IF the motor is to work on two speeds.

Can you remember if fan has worked on two speeds after correction work was done. Is there any chance whatsoever that someone messed with the motor wires then?

Cutting short and taping off wire doesn't sound like factory practice to me.