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

According to this you could be right
http://www.talkmorgan.com/ubbthreads.php?ubb=showflat&Main=2497&Number=24637#Post24637

If you put the headlights on do you have 2 fan speeds. I ask because the pcb on mine was playing up. There are power relays built into the pcb one for just the ignition and one for when the lights are on. Wiring the lights to be on with the ignition solved my issue.

The info I provided Rog was based on the 2006 -2014 Roadster parts book wiring schematics. These were drawn in 2004 though. In the case of heater fan control the cabling was clearly shown as running from fuse to conventional speed selector switch then via connector direct to fan motor with no PCB device intervention.

It may be that the drawings are incorrect in which case the juries out. It could also be that the loom was not adopted until after 2004 and a momentary switch was used earlier - perhaps Leroy could confirm? Certainly the momentary switching would require some form of latching provided by software control or relays.

I will add FWIW that the later 3.7 Roadsters have a conventional fan switch commanding the BCU which in turn controls the fan motor. Perhaps to allow interaction with optional aircon.

Richard on my S1 Roadster when the 1st PCB was playing up switching on the indicators with the wipers & fan already on stopped the heater fan. Don't ask me why. We changed the PCB & the problem stopped.

The PCB on the S1 is horribly exposed and the T piece for the washers pipes on mine leaked spraying it with washer fluid.

The 3.7l cars seem to have far better protected electrics. Touch wood.

Thanks John, so can I assume you had the momentary switch controlling two speed heater fan? If so I guess it worked sequentially i.e. slow, fast, off.

Yes it did. On the new PCB it started playing up , not the fan from memory but I noticed with the lights on it works fine & there are the 2 power relays built in. So I had the lights wired permanently on .

My foggy recollection is that car between 2004 and 2006 with the dash pcb had either a single or double speed fan. The fan switch looked to be a monetary type. See the pic below of my previous car. You can just make out the EAO part number of the switching actuator component of the switch assembly (71-611.0) which implies that its configured to function as momentary rather than latching.



Now the next bit is a total a guess…. Was the pcb capable of being either 1 or 2 speed depending on how it was populated? The pic below shows a pcb from car with a single speed fan and a relay missing. I’ve never seen a pic of a double speed pcb but maybe John’s original faulty pcb was a double? Do you still have it John, could you take a look?

Here are some pictures that show what's behind the control panel. Do these give any clues to what set up I've got. I tested the speed with the lights on and no difference. One thing, and this is only from memory, but I'm sure mine went from off, to fast, and then slow speed. 🤷‍♂️

I pulled all of those relay, which, if not clear from the picture are directly beneath the instrument panel. I pulled each one in turn with the fan blowing and I continued to blow, do guess neither of these relays relate to the blowers. I had a look behind the speedo area where Dave W said his roadster relays where but could see any. I guess my set up is different, and things are run from the pcb. Is it a big job to remove the pcb, and have the switch replaced? If it is, I won't bother as I can live with just one speed.

Thanks Leroy so you do have the sequential momentary switch control. The fact that slow is after fast has no great bearing.

The relays in your top pic have no relevance to heater fan control as mentioned above. It does seem that the likely culprit is the PCB though which provides the switch controlled logic to (I'm guessing) two miniature soldered in onboard relays. One to control power feeding to another to control speed. If it is a relay problem on this board it's likely the latter.

You could work back from motor itself checking power with the cable colour codes I gave above, but I expect you will find power on fast cable when fan is running but not on slow cable when selected.

Given scarcity and cost of new PCB added to difficulty of working on existing, it may be the best option to leave as is.