Electric Fan Connection

Hoghead said:
Those MG fans do not look like a very efficient blade design, but OTHO do not seem to block much of the rad core.
I wonder what the flow rate is for the pair?
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These are the same fans that are used on the later Spitfire too... and they aren't very efficient. Originally they were wired to continue running after the engine was shut off and the key in the "off" position.... In any event, electric fans (or even mechanical ones) don't do any good once the car is traveling over 15MPH, or so.. The problem with the Tiger is that there is nowhere for the air to escape from the engine bay.. Rootes ran the rally cars with the hood popped open. As it's hinged in the front there was no danger of it flying open.

There are a number of things that can be done to improve cooling. The first on my list was installing a radiator core with dimpled tubes. This slows the coolant down and holds in in the radiator longer so it can cool more efficiently. You do not want to fit a high flow water pump as this will only make the overheating problem worse. I use a 160 thermostat, have a 13lb cap, set the timing at about 12-15 degrees before TDC and set the carb slightly rich. Lean mixtures will cause the engine to run hotter, as will the timing being too far advanced. I have the 6 blade Maverick fan, and I have fit a reduced diameter water pump pulley (Robert Straghan--hoghead makes these). I also fit horn hole blanking plates, and as I have a MK2, I have an oil cooler.. I am also running stock exhaust manifolds, but with a 2" exhaust system.

Perhaps the single most effective thing I did was fit an LAT type hood, though I made mine from steel. My engine temps dropped by 15 degrees (F) from this alone. I live in north central Washington in a semi arid desert environment that usually has three weeks over 100 degrees in the summer. I had a Tiger pal come over who was dubious of the effectiveness of the hood. There were Willow leaves in the hood exhaust vents, when I started the car, the air flow from the mechanical fan blew them all out... Pretty obvious demonstration of their benefit!

The engine temp never gets above the center of the temp gauge, even on the hottest of days. In stop and go traffic in Seattle it has never overheated. I drive the car between 5-6000 miles a year and have NEVER overheated...
 
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Austin Healer said:
Green wires are hot with key on (fused). white wires are hot with key on, unfused... Brown are hot all the time, Purple are hot all the time, fused
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This is just the information I needed, thanks guys!

My car has a brand new stock harness in it. I was thinking of keeping this simple and not going with a fancy controller. Just have the fan run while the engine is running. I was considering putting in its own in-line 20 amp fuse and connecting it to a white spade connector. I also have a 6 blade flex fan installed and a Griffin radiator. Does that sound appropriate?
 
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My thought would be to totally isolate the cooling electric add on fan wiring and not use power source thru orig. style Sunbeam wiring harness. I would wire thru a separate fuse/relay direct to 12v on hot side of starter solenoid. I am not an electrical expert but from experience the overall design and gauge of original Sunbeam wiring harness (especially the newer repo's) seem best to work around rather than thru - just saying . Anything you add on requiring a lot of amps (like the cooling fan I would assume) might be best to do totally separate from original wiring harness IMO. Others, please chime in re. my 'thoughts' on this, and again I am NOT an electrical expert but have successfully re-wired many cars/trucks/RV's.
 
KettleCarver said:
I was thinking of keeping this simple and not going with a fancy controller. Just have the fan run while the engine is running. I was considering putting in its own in-line 20 amp fuse and connecting it to a white spade connector.
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I'd recommend not wiring fan to the switched circuit with no controller, IMO. They are noisy as heck, and it would run a lot when not needed, even while starting. Even if you use an inside manual on/off switch instead, chances are you may get distracted while your engine gets toasty. There are better things to do than watching your temp gauge while driving your Tiger. I've adjusted mine so fan comes on around 195-200, so it's usually off while at speed, and running at idle. I do like the idea of a variable speed controller like the Hayden preen suggested, but I'd have to mount that alien looking critter somewhere out of sight, at least on my old scruffy stock looking car.
 
I mounted it in front and to the side of the radiator, out of site. It is weatherproof, so no issue.
 
I don't have a photo. I just mounted to the bulkhead which holds the radiator. I was interested in this topic since I rigged it quickly so I could drive my Tiger after I bought it without overheating. I just ran the switched power from coil and the constant power from the solenoid. I haven't thought about how I will do it when I am ready for it. My car is a painted shell right now. I am color sanding and polishing the paint.
 
KenF said:
I'm thinking of installing an electric fan, hopefully to help keep it below 100º C on hot days, and see if I can put up with the noise. Controller has a ground switching circuit/relay, so needs a constant positive battery connection. Fan draws 13 amps.

Where and how are others connecting positive connections under the bonnet?

Thanks, Ken
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So.... some time ago I converted my brother's TR4A to a 302 with a T5 gearbox... He did this because of my Tiger, and that he already had the TR4A. He installed a Derale fan which can be wired to pull or push... He set it up as a puller fan... He wired this up with a switch on the dash that he could engage while (or if you're English, "whilst") on the move. He called me today and said when he engaged the fan, the engine would die and the voltage gauge would measure a (significant) drop. I am assuming that since he has a Pertronix unit, some of the problem was reduced voltage supply to the ignition. He brought it by, and it did exactly what he described. He had wired the voltage (+) feed to the fuse box and the negative (closing) circuit through the switch in the dash... It was pretty obvious that the amperage requirement of the fan was more than the connections could supply. Part of the problem was that the gauge of the wiring was inadequate. He had wired it with 20 ga, I wired it with 14 ga.

The solution.... I wired the positive feed for the fan directly to the solenoid/battery (a Ford unit identical to the Tiger) and then ran the ground portion of the circuit through the dash switch... worked and the stalling problem is gone. Obviously, this could also incorporate a temp sensor (on the ground side) of the circuit. This would allow the fan to continue to run, with the key off, like the MGB and Spitfire systems did from approx. 1975-1980.

One of the best guides I can give.... NEVER, EVER switch the power supply... only switch the ground. Lucas switches just are not designed for any kind of real load... otherwise you should fit relays if you insist on switching the positive side of the circuit...

In any event, electric fans, or even mechanical ones, are completely irrelevant at speeds above 15MPH... at that point, air flow through the radiator negates any benefit of a fan... If your car overheats while on the move, there is no electric fan on the planet that will help you. I've said this a million times... it's not getting air through the radiator on a Tiger, it's getting it out of the engine bay.
 
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Austin Healer said:
One of the best guides I can give.... NEVER, EVER switch the power supply... only switch the ground. Lucas switches just are not designed for any kind of real load... otherwise you should fit relays if you insist on switching the positive side of the circuit...
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The current through a switch (or relay) is the same whether you are on the 12V side or on the ground side, so it actually makes no difference on what side you put the switch, it's going to get equally melted in the long run.

I agree that the Lucas switches are not going to last at anything over maybe 10 amps, you should use a relay for any high load like fans, headlights, and the horn. The horn and motor loads (like a radiator or heater fan motor) are worse for switches because the inductive load causes a spark to jump the switch contacts when you turn it off. Over time that spark can damage the contacts or lead to conductive tracks inside the switch.

I'm currently running a 16 inch pusher fan with a thermo switch installed in this thermostat housing . The thermo switch, relay and circuit breaker were part of this Painless Wiring kit.
To fit that fan I cut out the lower radiator cross brace and made a new piece using some 18 gauge sheetmetal and some 1 inch 0.065 wall tubing, that mounts both the fan and the Griffin radiator. So far it's working well.
 
theo_s said:
The current through a switch (or relay) is the same whether you are on the 12V side or on the ground side, so it actually makes no difference on what side you put the switch, it's going to get equally melted in the long run.

I agree that the Lucas switches are not going to last at anything over maybe 10 amps, you should use a relay for any high load like fans, headlights, and the horn. The horn and motor loads (like a radiator or heater fan motor) are worse for switches because the inductive load causes a spark to jump the switch contacts when you turn it off. Over time that spark can damage the contacts or lead to conductive tracks inside the switch.

I'm currently running a 16 inch pusher fan with a thermo switch installed in this thermostat housing . The thermo switch, relay and circuit breaker were part of this Painless Wiring kit.
To fit that fan I cut out the lower radiator cross brace and made a new piece using some 18 gauge sheetmetal and some 1 inch 0.065 wall tubing, that mounts both the fan and the Griffin radiator. So far it's working well.
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I am looking into the Painless wiring kit that you recommended. Does that thermo switch also act as the temp sensor to feed the stock temp gauge? I have the thermostat housing that you are using and my temp sender is screwed into the spot where your thermo switch would go.
 
theo_s said:
The current through a switch (or relay) is the same whether you are on the 12V side or on the ground side, so it actually makes no difference on what side you put the switch, it's going to get equally melted in the long run.

I agree that the Lucas switches are not going to last at anything over maybe 10 amps, you should use a relay for any high load like fans, headlights, and the horn. The horn and motor loads (like a radiator or heater fan motor) are worse for switches because the inductive load causes a spark to jump the switch contacts when you turn it off. Over time that spark can damage the contacts or lead to conductive tracks inside the switch.

I'm currently running a 16 inch pusher fan with a thermo switch installed in this thermostat housing . The thermo switch, relay and circuit breaker were part of this Painless Wiring kit.
To fit that fan I cut out the lower radiator cross brace and made a new piece using some 18 gauge sheetmetal and some 1 inch 0.065 wall tubing, that mounts both the fan and the Griffin radiator. So far it's working well.
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This is precisely why the wiper switch is only a ground interrupt. The wiper motor itself is constantly wired to the power supply. (green wire to fuse block A3). When I wired up my driving lights (Lucas LR8's) i ran them through a Lucas 6RA relay as there is no way on earth that the switch would stand a 15 amp draw.

The headlight wiring is a weird call. No Brit car that I am aware of runs them through a relay. Jags and the Aston Martin DB5 run them through the fuse box. TR4-6, Jags and the Aston run the horns through a relay. The e-type runs the cooling fans through one as well, The Aston doesn't.

Basic rule of thumb, anything over 5 amps should probably be run through a relay. The current crop of repro Lucas flip switches are of indifferent quality, to say the least.
 
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An electric fan only is of benefit when the car is stationary... once the car is travelling at anything over about 10-15 MPH the volume of air supplied by movement will exceed the fan. In any event, the fan will only help if there is a path for the hot air to get out of the engine bay. This is why the Rootes comp. department ran the cars with the hoods open and only held by the safety catch.

I recently watched a segment on Engine Masters regarding headers and the heat thrown off of them... even with ceramic coatings or wrapped with the woven heat shield material, the heat was enormous.

I recently had to repair a Mk1 with a cut out radiator core support! When they did it, the center of the front valance had no support and was very quickly destroyed!

My car NEVER even gets to the center of the temp gauge, regardless of ambient temp. We have several months in the summer where it's regularly in the triple digits. I have an LAT fan, blanking plates for the horn holes, a special radiator core with dimpled tubes (slows the water down so it stays in the core longer). I have fitted one of "Hogheads" water pump pullies, but the water pump is standard issue. High flow pumps will just make it worse. As I have a MK2, the car has the factory oil cooler... it does make a difference. My timing is set at 10 BTDC (standard points w/ stock vac advance unit.) Idle mixture is set slightly on the rich side. as the leaner you set the mixtures, the hotter the car will run. I have the idle set at 900 rpm. Thermostat is a 160 degree unit as recommended. I am running stock cast exhaust manifolds with a 2" exhaust system (flowmasters and secondary resonators behind the rear tires). There is an "H" pipe behind the cruciform.

The engine is a mildly hopped up 302, close to 300HP.

With just this set of mods the car ran consistently in the center of the gauge. After I fit an LAT hood I noticed a further 20 degree drop in engine temps... mainly because now the hot air trapped under the hood has a way to escape.

And yes, I have verified the temp reading on the gauge... both with a candy thermometer in the exp. tank and with a laser temp tool....
 
KettleCarver said:
I am looking into the Painless wiring kit that you recommended. Does that thermo switch also act as the temp sensor to feed the stock temp gauge? I have the thermostat housing that you are using and my temp sender is screwed into the spot where your thermo switch would go.
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No, the thermo switch is just a switch. It turns on at a set temperature, then it turns off about 10 degrees below that temperature. I have the temperature gauge sender installed in the manifold, in the conventional location.
A possible issue with locating the temperature gauge in the thermostat housing, is that it is then on the 'wrong' side of the thermostat. What you'd see is that the gauge takes a long time to come up to any kind of temperature and then suddenly it will go whoosh up to the thermostat set point (when the thermostat opens). The close proximity of the sender to the thermostat will moderate that effect somewhat so it might be hard to see the difference between the thermostat housing mount, and the 'proper' location.
 
pfreen said:
I installed a Spal 001134054 11" pusher fan with a Hayden 3655 digital fan controller.
The Hayden controller is variable speed so the fan is noisy only in the hotest conditions.
It stopped the overheating in 95 degree Florida heat. Without it, it would overheat after 20 minutes of idling.
I have this controller on my Lotus , which has two 8" Spal pusher fans, and I have never had a problem in 5 years. I do not have an override switch, which in my way of thinking is unnecessary. New cars don't have this, why would they? If the controller failed, I would hot wire the fan and find a new controller.
I know many people install override switches and I am not criticizing. They are just not for me.
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I bought and installed a Spal 30102040 11" pusher fan, and installed it using steel brackets mounted in the existing Alpine holes. Now, I am moving onto the wiring. I have a few questions about that:

1) I am looking at the Hayden 3655 fan controller. If I am reading the description correctly, it appears to function as a controller and a relay. Is that correct, or did you use a separate relay?
2) Did you cut the connector off the Spal fan and splice the wires in? Or did you find an appropriate plug somewhere? If yes, where?
3) I plan on using the included probe, installed in the radiator fins.
4) where did you pull your continuous power from?
5) Where did you pull your switched power from?
6) The Hayden unit comes with a 25 amp fuse. The Spal says "for use with a 30 amp fuse". Is that going to cause problems?

Thanks!
 
1. No relay is needed. It uses pulse width modulation to control the fan speed.
2. I am not around the car to check but I think I spliced it to connect.
3. I used the enclosed sensor and inserted it in the radiator fins.
4. I pulled continuous power from the starter solenoid.
5. The ignition/switch power came from the brake switch.
6. I don't remember but I think I used the included fuse. Does your fan pull more current than the fan I used?

I use this controller on my Lotus and it controls two 9" Spal fans. My Lotus has air conditioning, thus the large flow rate from two fans. It works great.
 
pfreen said:
1. No relay is needed. It uses pulse width modulation to control the fan speed.
2. I am not around the car to check but I think I spliced it to connect.
3. I used the enclosed sensor and inserted it in the radiator fins.
4. I pulled continuous power from the starter solenoid.
5. The ignition/switch power came from the brake switch.
6. I don't remember but I think I used the included fuse. Does your fan pull more current than the fan I used?

I use this controller on my Lotus and it controls two 9" Spal fans. My Lotus has air conditioning, thus the large flow rate from two fans. It works great.
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Thanks for the replies!
 
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