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

I wonder if the wiring might be the same as the V8 it replaced, although you bang on with the green/slate wire. What makes the loom difficult to access, it it joins the loom right at the point it exits the grommit. I've split the tape at the spur and definitely only 2wires from the loom. At some point I might remove the tape from the loom via the drivers footwell as that's where it goes through to the engine bay, and look for the corresponding wires as I don't like leaving puzzles unsolved.

I think its highly likely that I mistakingly believed I had a slow speed, as logic doesn't stack up with my belief.

You could well be right that an early Roadster model such as yours had some interim unacknowledged loom fitted although it does have the PCB. Was this latter item ever fitted to Plus 8's I wonder. It's certainly an integral part to the one touch sequential switch operation. Guess we will never know. At least you now know how to choose the one speed you have available. Phew! what a struggle

Wow what a thread! Well done.

Richard, Yes I believe a similar type pcb was at least used in the 2002 Plus 8 Le mans 62. Don’t know if it was 1 or 2 speed though

Leroy, It’s that Mandela effect again. It catches me out all the time!

Quite possibly Rog. But one thing for sure, thanks to those in this thread, I know a lot more about my mog. Especially the mess of wires behind the dash 😬😂

I've been reading this thread with interest, while not exactly the same as the OP's 'no fan in the slow speed setting' issue, my fault does have a lot of similarities. I'm new to Morganeering so please forgive my silly question, but on my 2011 Duratec Plus 4 the heater fan switch has two distinct clicks so I'm assuming it should be offering two two distinct fan speeds... i.e. slow & fast?

I ask because despite the two positions of the switch, I only seem to have one fan speed:

* Fan switch in position 1 = Fast

* Fan switch in position 2 = Fast too, it's exactly the same speed as position 1 and is the reason for my post.

Question: Am I correct in assuming I've somehow lost the slow fan speed mode when the fan switch is position 1?

I have to say the heater is amazingly powerful, so good in fact I could really do with a slower fan speed with the fan switch in position 1. I'm reading a lot about potentially faulty PCBs in this thread which isn't something I'd want to start messing with, so I'm considering a work around solution could simply be to find the slow speed circuit out of the back of the two position fan switch, and add a variable resistor?

This way I could tune my switch position 1 to a fan speed of my liking thus solving the issue while at the same time leaving the PCB well alone, I'm aware Rog has a 2011 4 too so his comments on the correct operation of my heater fan switch are especially welcomed, but I'm also keen to receive general opinions from all on the viability my variable resistor idea.

Thanks, Dave.

Dave, all the recent models use a two speed fan motor. I imagine there are two field tappings to give differing speeds. The speed switch operates fan motor either directly or via a PCB with miniature relays or on later Plus 4's via the BCM (body control unit) which will likely also have miniature relays within. Rog will know which.

Either way you could check by breaking fan connector near motor and measuring voltage between ground and green/slate (slow) or green/yellow (fast) wires found on chassis loom side of connector. Each one should be found live (with ignition on) according to speed selection.

FWIW I don't think messing with serial resistors is a good idea.

Dave I’m having the same problem as Leroy. I can’t be sure if my car is 1 or 2 speed. Pretty dam sure it is 2 but will check when I get back. It could have all changed of course since the last time I used it owing to that Mandela effect.

As Richard said I think just a variable resistor or pot is a no no. If I understand correctly as to what you are planning I think I would perhaps try a separate PWM controller (pulse width modulated) to control the fan motor high speed? You can pick them up ever so cheap so not worth making one. There are loads available but here is one that might work for you? (deactivate the reverse or use a simpler one that dosent do reverse)

These might be useful but not mine.


Re that dodgy pcb. I’m desperate to get my hands on a knackered one to actually understand what is going on as I have probs with mine. And maybe with a view to replacing it for good...

Dave, I have heater fan issues as well but not quite the same as yours. Mine blows the fuse if I turn to the high speed ( same fuse as the speedometer). I think this is the same PCB issue that Peter (gambalunga) had and subsequently removed the PCB and wired everything?

I've not removed the dashboard to check it out yet but I suspect a rewire with relays will be the way forward.

Regarding your powerful heater, you might find the heater box is not sealed to the underside of the bonnet, mine wasn't. This is great in cooler climates but when touring Italy in 40° it wasn't pleasant as you can never get cold air into the cabin. I increased the seal height on top of the heater box to make contact with the closed bonnet and the heater is now much more controllable.

Ditto I have done that with an extra layer of foam.
When I bought my 06 S1 secondhand I seem to remember Phil at AW telling me it had a one speed & being pleased to find 2 speeds. Maybe earlier ones only had 1 hence the cut wire?