Twin Electric Fans

It turns out that Freelander cooling fans are an ideal fit onto a Defender radiator:

fuddymuckers.co.uk_gallery_s_300_127_img_2942.jpg

A small trim along the bottom edge, added a strip of aluminium to seat in the original clips that hold the old fan cowling. Hard to see but it just needs a Z-channel or similar to drop into the two clips on the bottom of the rad frame. An original Defender cowling screw or two secures the top edge nicely.

How to find them
I've been asked a few times which model these fans came from. I think it was TD4 but the easy way to tell is go to the scrapyard (or eBay) and look. If they look like this, they're these ones. If they don't, they're not. :thefinger:

Wiring

Our fans are controlled by the Megasquirt ECU in two stages - one fan comes on 1st, if the temperature goes higher the 2nd comes on. It works nicely but is not as nice as the setup on the 109 which switches both fans in series 1st, so they get 6v each and run quietly at about half speed, then switches them into parallel so they both run full speed. This seems to give a quieter and smoother result at the expense of using 4 relays where 2 will do.

I discovered whilst reading up on the wiring diagram for the FL fans that Land Rover themselves do this, and there is in fact a fan relay module in the Freelander that contains 4 relays on one PCB! Anyway, £20 later on eBay and I have no less than 3 of these to play with - it's on the to-do list, I'll post my results when I get round to it.

The Original Circuit

Credit goes to Ian / Bull bar Cowboy from LR4x4 for designing this, I've copy-pasted it here for now:

Application Description

Although this article applies to the Rover V8, you can easily adapt it to any engine if you know the normal operating temperatures.

When the V8 EFI was transplanted into the 90, it quickly became evident that the Rover standard fit of a junior propeller had to go and be replaced by an electrical fan arrangement.

The fans are Vauxhall Astra MkIII. The fans are laid face down and the triangular mounting parts of the fans are cut away, this then allows the two fans to be bolted to give a twin fan setup. The top and bottom of the fans are then joined using a short strip of stainless steel with a thickness of 1.5mm. This assembly is then mounted on the rear of the radiator using stainless steel “L” brackets. The built in cowls of each fan are in contact with the radiator thus providing a very good thermal air path. You can use any pair of fans you wish, though.

Control of the fans is achieved by the use of a dual thermal radiator switch (Intermotor 50091), which is mounted into the top hose. These switches are a standard fit item on many models and thus easily sourced in a variety of different temperature characteristics.

Note: This bit is kinda superseded by the X-Eng fan switch but I've included it for completeness:

The “splice” fitting for the top hose is constructed from a short length of 38mm diameter thick walled brass tube. The tube is machined (or drilled and filed) to take a standard 22mm temperature switch radiator fitting. These can be obtained very cheaply from most good radiator specialists. Alternatively a 16mm brass compression pipe fitting can be used as this has a 22mm internal thread (not to be confused with the standard 15mm pipe fitting that has a BSP thread).The fitting is then soldered into the brass tube which is mounted close to the radiator.

An alternative method is to use the thermostat housing from an export or “air-con” model as this is designed to take the thermal switch (the air con models have a 100°C switch fitted). However, the housing is in the order of £45 +VAT. As the coolant is some 6°C to 8°C cooler at the radiator entry point than the engine block , a switch fitted in the thermostat housing will need to reflect this difference (use a 50174).

The dual speed switching came about as it was found that both fans running at normal speed were too efficient - @ tickover, the fans were set to come on at 100°C and would cool the engine coolant to thermostat temperature in 15 seconds. Unfortunately that amount of heating / rapid cooling is bad news for the expansion and contraction stresses of the radiator and engine components. To overcome this it was decided to run the fans in series (a bit less than half speed) when the engine temperature rose to circa 95°C and to run them on full speed if the engine temperature further rose to 100°C. In practice the fans only come on when sitting in stationary traffic (the slow speed gently cools the engine down to 90°C and keeps it there) or when towing (on hills). Only once have I had the fans come onto full speed - the radiator was completely clogged with mud and I had driven from Wiltshire to Devon with the fans on slow most of the way, but at telegraph hill the engine temp rose to the magical 100°C. However the fans did the trick and the engine temp dropped back sufficiently.

Much of my work is in the design of Radio systems for Public Safety (mainly Fire and Ambulance related) where any single point of failure is designed out - hence two fans, dual switching etc - get the picture!

Diagram Description

The master switch controls the supply to the thermal switch (s). In its off position it turns on one of the spare dash lights (amber, in the bottom right hand corner). Closure of the first thermal switch at 88°C (engine temp of 95°C - remember the 6°C - 8°C temperature difference between coolant in block and coolant in top hose) operates relay A. This completes the circuit of — supply to Fan 1, via normally closed relay D contacts to Fan 2. This connects the fans in series and under normal circumstances will give more than adequate cooling.

If you are giving the engine a hard time and the temperature rises to 100C the second thermal switch will close and operate relays B and D. Relay D contacts will change over and a supply via the relay B contacts will be directly applied to Fan 2 The closure of Relay B contacts causes relay C to operate and apply an earth to the negative side of Fan 1. Relay C also ensures an appropriate delay in applying the earth (if this feature was not included there was a possibility of intermittent fuse blowing dependant upon relay timing). This arrangement now allows the fans to run at full speed (parallel operation). A further feed is also taken back to the dash lights as a warning that the fans are on full (I used the spare green light - top row centre)

The supplies to the fans should come directly from the battery (Starter motor in most cases, as this in the shortest run). I run the feed to the main switch as a direct fused live, because having the fans remain on when the engine in switched off (and they then come on intermittently as thermo siphoning takes place in the cooling system) causes less long term engine bay problems due to heat soak.

Attached is a list of INTERMOTOR switches that are readily available for this application (I have listed all types, but the M22 switches are of most interest)

Part No. A/F1) Size Thread Temp °C
50480 19 3/8“ BSP Taper 50-46 N.C.C.
50471 19 3/8” BSP Taper 77-74 N.C.C.
50460 27 3/8“ BSP Taper 90-85
50370 27 3/8” BSP Taper 95-90
50372 27 3/8“ BSP Taper 100-95
50010 25 3/8” x 18 NPTF 79-74
50080 21 3/8“ x 18 NPTF 88
50172 22 M14 x 1.5 87-82
50042 24 M14 x 1.5 90-85/98-93
50041 22 M14 x 1.5 95-90
50173 22 M14 x 1.5 100-95
50040 22 M14 x 1.5 103-98
50481 21 M16 x 1.5 50 OFF N.C.C.
50475 17 M16 x 1.5 60 OFF N.C.C.
50430 17 M16 x 1.5 85 ON
50320 27 M16 x 1.5 85-80
50420 21 M16 x 1.5 85-80
50432 21 M16 x 1.5 85-80
50476 17 M16 x 1.5 85-80 N.C.C.
50300 27 M16 x 1.5 87-80
50317 22 M16 x 1.5 87-82
50321 22 M16 x 1.5 88-79
50310 22 M16 x 1.5 88-86
50301 22 M16 x 1.5 90-83
50474 19 M16 x 1.5 90-83 N.C.C.
50461 21 M16 x 1.5 90-85
50421 21 M16 x 1.5 90-85
50470 17 M16 x 1.5 90-85 N.C.C.
50390 17 M16 x 1.5 90-85 N.C.C.
50316 22 M16 x 1.5 92-82
50330 22 M16 x 1.5 92-82
50453 24 M16 x 1.5 92-85
50315 22 M16 x 1.5 92-87
50341 24 M16 x 1.5 92-87
50342 24 M16 x 1.5 92-87
50371 27 M16 x 1.5 92-87
50373 24 M16 x 1.5 92-87
50450 21 M16 x 1.5 92-87
50340 29 M16 x 1.5 93-86
50374 24 M16 x 1.5 93-88
50479 17 M16 x 1.5 93-88 N.C.C.
50332 22 M16 x 1.5 95-85
50477 17 M16 x 1.5 95-88 N.C.C.
50455 22 M16 x 1.5 95-90
50454 22 M16 x 1.5 95-90
50380 17 M16 x 1.5 97-92 N.C.C.
50478 17 M16 x 1.5 98-91 N.C.C.
50375 24 M16 x 1.5 98-93
50472 17 M16 x 1.5 98-93 N.C.C.
50473 17 M16 x 1.5 98-95 N.C.C.
50431 17 M16 x 1.5 100-95
50331 22 M16 x 1.5 102-97
50100 29 M22 x 1.5 82-68
50101 29 M22 x 1.5 84-79/88-83
50250 29 M22 x 1.5 86-76
50012 29 M22 x 1.5 86-77
50090 29 M22 x 1.5 86-81
50120 29 M22 x 1.5 88-79
50295 29 M22 x 1.5 88-79
50296 29 M22 x 1.5 88-79/110-102
50271 29 M22 x 1.5 88-83
50272 29 M22 x 1.5 88-83
50275 29 M22 x 1.5 88-83
50217 29 M22 x 1.5 88-83/92-87
50091 29 M22 x 1.5 88-83/92-87
50212 29 M22 x 1.5 88-83/92-87
50213 29 M22 x 1.5 88-83/92-87
50216 29 M22 x 1.5 88-83/92-87
50221 29 M22 x 1.5 88-83/92-87
50219 29 M22 x 1.5 88-83/92-97
50240 29 M22 x 1.5 90-80
50110 29 M22 x 1.5 92-82
50111 29 M22 x 1.5 92-82
50112 29 M22 x 1.5 92-82
50113 29 M22 x 1.5 92-82/95-80
50218 29 M22 x 1.5 92-82/97-92
50170 29 M22 x 1.5 92-87
50200 29 M22 x 1.5 92-87
50210 29 M22 x 1.5 92-87
50211 29 M22 x 1.5 92-87
50220 29 M22 x 1.5 92-87
50230 29 M22 x 1.5 92-87
50231 29 M22 x 1.5 92-87
50235 29 M22 x 1.5 92-87
50260 29 M22 x 1.5 92-87
50270 29 M22 x 1.5 92-87
50280 29 M22 x 1.5 92-87
50281 29 M22 x 1.5 92-87
50285 29 M22 x 1.5 92-87
50290 29 M22 x 1.5 92-87
50215 29 M22 x 1.5 92-87/97-92
50011 29 M22 x 1.5 93-88
50102 29 M22 x 1.5 93-88/97-92
50035 29 M22 x 1.5 95-85/102-92
50130 29 M22 x 1.5 95-86
50030 29 M22 x 1.5 95-90
50033 29 M22 x 1.5 95-90
50061 29 M22 x 1.5 95-90
50062 29 M22 x 1.5 95-90
50160 29 M22 x 1.5 95-90
50092 29 M22 x 1.5 95-90/100-95
50174 29 M22 x 1.5 95-90/100-95
50104 29 M22 x 1.5 97-92
50282 29 M22 x 1.5 97-92
50103 29 M22 x 1.5 97-92/101 -96
50214 29 M22 x 1.5 97-92/102-97
50190 29 M22 x 1.5 100-95
50195 29 M22 x 1.5 100-95
50196 29 M22 x 1.5 100-95
50197 29 M22 x 1.5 100-95
50198 29 M22 x 1.5 100-95/110-105
50000 29 M22 x 1.5 103-98
50013 29 M22 x 1.5 103-98
50014 29 M22 x 1.5 103-98
50191 29 M22 x 1.5 120-115
1) Across Flats
alfie/electric_fans.txt · Last modified: 2017/09/06 09:18 by jin
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