Talk Morgan Forums Morgan Sports Cars Classic Morgans (pre-CX) Plus 4 radiator fan spring “thing”

OK …. I’ve googled enough Please can someone tell me what is this spring device at the rear of the radiator fan ?

That looks like a high wattage resistor to me dissipating a lot of heat hence the shield, not seen one of those on a Mog before.

Series resistor to provide low fan speed, operated by relay. Not sure what year your car is but two dedicated relays usually employed, one for high and one for low speed.

Yes, the resistor for low speed fan. My 2011 +4 has one. More easily seen by looking up from underneath as it is fixed to the X shaped bracing plate on the crosshead.

My previous S1 Roadster had one

A general watchpoint are the connectors to and from because they are very exposed to water ingress whilst driving leading to corrosion, and the high amperage the fan + resistor uses leads to a non-op fan when least expected, mine got so hot it melted the insulation because it's a 20 or even 30 amp ? fuse which in my opinion was too high for the cable size MMC used

Yes fan circuit fused are 30 amps. The motor probably takes a nominal 20 amps.

My 2012 +4 has one too, I can only assume Morgan wanted the low & high-speed feature for refinement, i.e. lower fan noise on low speed? A big old resistor like that is a very old school idea that in my opinion only serves to introduce a potential point of failure, these days you’d use PWM to give a temp referenced and infinitely variable fan speed arrangement.

Admittedly Monty does have a seemingly very efficient Mulfab aluminium radiator, but my EMU Black ECU logs show super stable coolant temps within a very tight operating range from 83c minimum even when driving at speed on a cool day, to 86c in stop start traffic on a warm day.

If like me you're more familiar with a traditional arrangement, the thermostat system on a Duratec is a bit unconventional, but it clearly works well as my temp logs prove. The setup seems supremely adept at regulating coolant temperature, and largely without the need for assistance from the rad fan.

My ECU triggers the high-speed fan relay only, I've set activation at 93c, even idling in traffic on a warm day it takes some minutes before the coolant reaches my trigger temp and the fan chimes in, under normal mixed driving conditions including some town driving it's quite common to never experience fan activation at all.

Monty's cooling system is clearly very under stressed and superbly well regulated by the Duratec thermostat system alone, I’m seeing an extremely rapid warm up phase and consistantly that nice tight 83 - 86c operating range, and all this with very infrequent fan assistance required. Given my data supported experience, I can’t help feeling Morgan’s low speed idea is an unnecessary complication. Old-school big resistors like the one shown are also a point of high heat and ultimately potential failure, the thing clearly gets so hot a heat shield was deemed nessesary, for many reasons that's far from ideal.

I also have to say on the rare occasion my high speed only fan does chime in, it really isn’t that noisy anyway, and with fan-on time so short anyway (10-15seconds max) I just don’t see the point of triggering the low-speed circuit.

Bear in mind Dave the horrible plastic side tank OE rad had a sealing cowl with vent flaps between rad and fan. This added considerable noise even with fan on low speed. Fitting the larger aluminium replacement rad, with fan swapped to fit direct to inner side, not only much reduced the occasions of fan running but also noticeably reduced the noise when it did.

MMC's adoption of the Ford Cyclone engine in the last Roadster series provides a setup with very well constrained temperature control with similar tight range to yours. Good enough to maintain identical warm up and control after fitting larger aluminium rad. The only time I've ever seen the gauge move from just below midscale once warmed up was following a dyno run when it hit a tad over 100°C.

BTW later cars have a less fragile covered resistor remotely mounted low down and shown below, the white cube shaped item described as "Ford resistor" on schematic. It's cabling runs to connector above, feeding current to fan from one of two relays with the high speed one bypassing resistor.



Note that short cables to motor aside (shown far right), the cabling from relays is commensurate with the higher currents taken.

I challenge anyone with a standard plastic tank radiator to bypass the the low speed fan relay (and stupid resistor), and report back here on what happens?

I'd put money on it being just fine

It's a pointless and unessesarily complication that only serves to introduce a point of failure for absolutely zero benefit.

Dave.

Low speed quieter though