Wiring an Electric Fan

[Alan_Myers]

Hi again,

First of all, I looked up the kit I purchased at www.summitracing.com ... it's their part # SUM-890015 and includes the circuit breaker.

For additional info about the pluses and minuses of using a circuit breaker instead of a fuse, or using a self-resetting circuit breaker instead of a manually reset one, go to https://www.bcae1.com/cirbrakr.htm

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As to the sensor's temp rating, I think TRs need to be pretty cool, around 180F on/170F off. I'm going to be running that with a 160F thermostat, so the T'stat should always be fully open before the fan kicks in.


[/ QUOTE ]Alan--Unless WOT racing, I think you will find the 160 stat is way too cool--both engine performance fuel economy will decline. Not an advisable change IMHO.

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Well, I agree that keeping an engine *too cool* after warm up can hurt engine performance and fuel economy.

But, sorry,I have to respectfully disagree that a 165F thermostat is overly cool (note: a slight correction from my earlier response... it's a 165F, not 160F).

For one, my car is a 4-cylinder TR, and there ain't no such thing as "too cool" with one of those! Most cooling system problems have to do with "too hot". I've been using a 165F in my TR4 for over 25 years now. But I know it doesn't effect running temps, either way, after initial warm up.

I notice that, according to the shop manual for the 6 cylinder TR, 180F "normal" and 190F "cold climate" thermostats were originally what was offered. But, I see TRF and others now offer 165F, too.

Basically, any thermostat serves only to delay coolant circulation until an engine reaches a minimum temperature. Once that minimum operating temp is reached, the thermostat is no longer in play for all practical purposes.

In other words, so long as a thermostat doesn't have *too high* a temp rating that would cause it to delay cooling for too long, it will have almost nothing to do with actual operating temps once it's fully opened.

The cooling fan and it's actuating thermoswitch will have primary effect and control of warmed-up, running temperatures. 170F is the shut off point for the fan, measured at the lower hose where coolant is returning to the engine. Temperatures at the upper hose, i.e. coolant exiting the engine, will undoubtedly be higher.

The primary purpose of choosing a 195F "winter" or 180F "normal" or 165F "summer" is to better accomodate the car's heater for the comfort of driver and passenger. With a 195F thermostat, the heater will provide toasty air faster than with a 165F.

My car doesn't happen to have a heater installed, so I simply want the cooliing system circulating fully at the lowest *reasonable* temperature.

Besides, I'm running Weber DCOE on the TR and my "Triumph Support Vehicle" is a Land Rover... so fuel economy musn't be very high on my priority list, although maybe it should be at today's prices! /ubbthreads/images/graemlins/frown.gif

 

[Alan_Myers]

Re: Circuit Breakers [was: Wiring Electric Fan]

Hi again all,

I was by my neighborhood auto parts store and noticed they have the circuit breaker mentioned earlier, right there hanging on shelves. It's in the fuse area, made by Buss and can be bought in 20 amp or 30 amp versions.

There are several types of miniature circuit breakers for automotive application.

The type I'm using is self-resetting, has a bracket attached for mounting and uses two threaded terminals to attach wires. It's enclosed in a rectangular metal case, similar to older Lucas relays. Cost at the local store was $4.

You'll also probably find slightly smaller, manually reset circuit breakers. These won't reset until the current to the circuit is momentarily interrupted. This could mean turning the ignition off, or flipping a switch, depending upon how the circuit is wired in any particular application. (Since I am wiring the electric fan in my car to be hot all the time, i.e. it might run after the ignition is shut off, this type breaker isn't what I'd use. But, your application may differ.) The local store had these in 20 and 30 amp versions, too. Price was also about $4.

A third type of circuit breaker replaces blade-type fuses very simply and directly. I found these in both self-resetting and manually reset types. This type breaker came in the widest variety of amperage ratings, similar to what's found in fuses. I forget the price being charged locally, but it was about the same as the other types of breakers, I think.

Hope this helps!

 

[vettedog72]

Alan:
When you state:
"In other words, so long as a thermostat doesn't have *too high* a temp rating that would cause it to delay cooling for too long, it will have almost nothing to do with actual operating temps once it's fully opened."

I had intuition that the thermostat actually modulated the flow of water to maintain a constant temperature. No argument about fully open as that means the cooling water from the radiator is insufficient (or near so) to keep the temp within the therm's limits.

 

[Alan_Myers]

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I had intuition that the thermostat actually modulated the flow of water to maintain a constant temperature. No argument about fully open as that means the cooling water from the radiator is insufficient (or near so) to keep the temp within the therm's limits.

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Hi again,

Yes. My earlier response didn't really try to get into that. In most engines the thermostat also provides some restriction of flow, and in that respect helps maintain even cooling. But what I'm saying is that this isn't due to the opening and closing of the thermostat itself, after the first few minutes of running and once the thermostat is fully open.

For example, if three thermostats were compared - identical in all design and dimensions except for their low, normal and high temperature ratings - the only functional difference between them would be how quickly the engine reaches its typical operating temperature.

This is because the engine's operating temp is higher than any of those thermostats' ratings. Once that temp has been reached, all three thermostats will have already opened fully and will remain open. All three will provide the same continuing effect on flow and cooling in the warmed up condition.

So, just changing a thermostat's rating will not effect the running temps of the engine in its warmed up state.

The restriction of a fully warmed and wide open thermostat does still help slow down coolant flow, keep it from pulsing, etc.

This is important because in most cases a water pump's rotation is tied to engine rpm. At high rpms the pump can actually move coolant out of the engine or through the radiator too quickly: not giving heat enough time to properly transfer from the engine to the coolant, or before heat is exchanged by the cooling effects of the radiator.

There is another possible problem. At high rpms a water pump might cavitate. That's a condition where the vanes are moving so fast they simply create a sort of eddy around themselves and actually move less coolant through the system. When and if this occurs depends upon the design of the pump's impellors and housing. But, the restriction provided by the thermostat, keeping coolant from moving too rapidly across the water pump's vanes, might also have some effect.

Hope this clarifies why I still maintain that swapping back and forth among Summer, Normal or Winter type thermostats will have no effect on normal operating temps, only on how quickly the engine warms up.