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TR4/4A TR4a Cooling system temperatures

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richie

richie

Senior Member
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Hi all, with the rewire from Advanced Auto Wire, I am looking to simplify the cooling fan system and eliminate the mechanical fan (Patton Machine) and setup a thermostatically controlled electric fan. The trouble is I need to decide which thermoswitch!

From the research I've done, it appears the general rule of thumb is that engines operate 5-10 degrees warmer than their thermostat rating (165). To prevent the fan from running all the time, getting the right on/off ratings is critical. With limited choices, I'm thinking I will try 185 ON 170 OFF, but am searching for some more advice on the matter before deciding.

Thanks!
 
I run an electric fan only on my Ford F100. It uses a 185 thermostat. I have a 200 on 185 off thermoswitch plus a manually dash operated on off. Soon after the install, I found I was always flicking the manual switch on (when I saw I'd be stuck at the red light, or the traffic was crawling) way before the thermoswitch kicked in.
While I don't have either Triumph with an electric fan, I think a 185 on 170 off switch would have the fan running too often - just my opinion.
 
Look into a Derale Cooling Products 16749 system. It's an adjustable controller. I plan to buy it and replace my current sensor on at 190 and off at 180. It looks like a well thought out item.
 
3798j said:
I run an electric fan only on my Ford F100. It uses a 185 thermostat. I have a 200 on 185 off thermoswitch plus a manually dash operated on off. Soon after the install, I found I was always flicking the manual switch on (when I saw I'd be stuck at the red light, or the traffic was crawling) way before the thermoswitch kicked in.
While I don't have either Triumph with an electric fan, I think a 185 on 170 off switch would have the fan running too often - just my opinion.
Click to expand...

Hey Jay, thanks for the response.

I'm curious why you think that when with your setup you find your ON setting of 15 degrees over thermostat not cycling enough yet my ON setting would be 20 degrees above thermostat opening?
 
JerryVV said:
Look into a Derale Cooling Products 16749 system. It's an adjustable controller. I plan to buy it and replace my current sensor on at 190 and off at 180. It looks like a well thought out item.
Click to expand...

Hey Jerry! I was looking into that unit this morning but then after reading quite a few negative experiences on it over at amazon, I am little hesitant. I love the idea but even after reading the installation guide, I am unsure on the on/off differential (most thermo switches seem to have a 15 degree differential) and the precision of adjustment. However, on the flip-side, adjustability would be fantastic for tweaking it just right!
 
Interesting comments but I still think I'll be getting the kit. 15 degrees differential is OK. My 4A never comes on when driving at any speed above 20mph. One of the best improvements is to install a Richard Good shroud for the 4A. Great product. With a good radiator but a broken thermostat (open) I could not get my temperature above about 120 at highway speeds. Pushing air through the radiator works wonders <grin>.
 
One important question is where you are going to mount the switch. I have mine mounted where it (mostly) sees the cool water returning from the radiator, and set to about 190 on, 195 off. I also use a modern 185 thermostat, the result suits me very well. The fan runs perhaps more often than absolutely necessary, but only for a few seconds (less than a minute) at a time and the gauge never goes quite past the '5' in '185'.

I believe the reason the off-the-shelf controllers use so much hysteresis (the difference between on & off) is so they won't be fooled by the sudden drop in battery voltage when the fan kicks in. That's my biggest problem at the moment with my home-brew controller : Sometimes under just the right conditions, the fan relay will chatter. When I get around to doing version 3.0, I'll use a voltage regulator to feed the temperature sensor. (Probably just a big RC filter on the 12v supply line would do fine, but I also plan to incorporate a small microprocessor so I'll already have the regulator for that.)
 
JerryVV said:
With a good radiator but a broken thermostat (open) I could not get my temperature above about 120 at highway speeds. Pushing air through the radiator works wonders <grin>.
Click to expand...

Hey Jerry-

Drop down our way in Houston for a visit sometime around August - we'll fix that underheating at speed problem for you :smile:
 
Randy, I bet you could. Seems like you Texas folks come our way to escape the heat most often. Are you and the group planning a trip our way this year?
 
richie said:
Hey Jay, thanks for the response.

I'm curious why you think that when with your setup you find your ON setting of 15 degrees over thermostat not cycling enough yet my ON setting would be 20 degrees above thermostat opening?
Click to expand...
Richie, Only was trying to convey what I found. With a relatively high out put V8, if I let it go to the 200 degree mark and waited for the fan to turn on (on a hot summer day), the fan never would "catch up" if I remained in stop and go traffic - the temperature would still climb. If I manually switch the fan on when I see the possibility of a prolonged stop, temperatures don't climb as much. By the way, I have the sensor mounted high on the radiator.
 
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