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

For some reason I've lost the slower speed of my heater fan. It's either off, if full blast. Not that it's causing me an issue, but there's clearly a fault somehow. Any ideas how to remedy it? Thanks

I think you will find it's the switch.

I thought “how on earth did he find that out in this weather” then I saw “South Shields”

😂 Yes. Was in Northumberland for a spirited drive, and it turned very foggy. Had to give the wipers a good outing. Good thing about the North is we don't get hose pipe band. Unfortunately there's a reason for that 😑

The light changes with each press, so there's power to it on each setting, but I'm no electrical expert so will look into that.

There are 2 relays that control low and high speed. I guess behind the dashboard on your model, arranged in a line of 5 side by side. I think the fan ones are usually the two on the right,. That’s the first place I would look. If you don’t have a spare, try interchanging them to see if it works. Only replace with diode relays.

Same problem and reason on my car! Since that time I always have two spare relay with me -- äh in my car!

IIRR in my left-hand 2005 (2006) 4/4 the fan relays are the first two on the left.

There are two cooling fan relays in the bank of five you refer to Doug, with the other three covering ECU, fuel pump and start and no others showing up on main wiring schemantic.

The dashboard subharness shows the heater switch with three connections hooking via 12 way connector into main loom and on to heater motor itself via bullet connectors with green/white and green/yellow cables energised for fan slow and fast respectively plus black cable providing ground. No relays involved!

As suggested by Keith I would suspect the low speed contacts on switch u/s. It could of course be the fan motor itself not completing the low speed circuit - possibly because its internal dropper resistor is burnt out.

If checking power out of switch itself with a voltmeter note the output cable codes are green/slate (slow) and green/yellow. Each should show 12 volts WRT ground when selected, with ignition on of course.

Richard: You are correct of course; I just need to book another appointment with Specsavers!

On a 2004 Roadster wouldn’t the heater fan relays be integrated into the dash pcb and controlled by the momentary fan switch that’s also mounted on the pcb?