Home » Public Forums » GMCnet » [GMCnet] Where did you put ur temp sensor for an electronic fan clutch?
| [GMCnet] Where did you put ur temp sensor for an electronic fan clutch? [message #352691] |
Tue, 10 March 2020 10:17  |
Thomas Pryor
Messages: 143
Registered: January 2011
Karma: 1
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Senior Member |
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Well my name has emerged too many times, so I will have to offer my input.
Let's us go back to the Thermal spring in our old Viscous clutches....What
activated it, heat from the radiator, yes?
The idiot light and subsequent temperature gauges were connected to thermal
output devices (sensors) in the engine........ BUT DID NOT CONTROL THE FAN
ACTUATION, YES?
With that as the foundation for our thoughts to activate the Electronic
Viscous Fan clutch, it makes perfect sense that we really want this new
device to act like our old Fan clutch, just more reliably, with a dash
switch over ride, and measure coolant rather than hot air. We also get
the added benefit of double the air flow (CFM).
That said, CURRENTLY when the controller sees 210 degrees coolant output
from the radiator it activates the fan. The fan will remain activated
until it sees a 15 degree drop (195).
Coolant in the radiator will fluctuate between those two temperature
regardless of the temperature gage on the dash! Just like the old days,
yes?
Thing is, we don't really know the activation points of the old bimetal
spring....... it turned on and turned off. When the dash light turned on
or the dash gauge went above 212 we changed out the Fan Clutch. We
operated, fat, dumb, but happy! Based on all my investigations and
discussions with Dick Patterson we are not going to degrade the life of any
engine. Now we just have more input data and can tweak if and when
required.
Thats my story, but I am willing to listen to any and all input.
Tom Pryor
4188 Limerick Dr
Lake Wales, Fl 33859
Cell 248 470 9186
1977 23'B named "CASPER", HARDLY ORIGINAL, (455 EFI) (Pwr. Drive)
(tailgate) (rear bunk beds)
(Webasto petrol boiler) (MB Elect fan clutch) (Brake reaction arms) BUT
STILL A WORK IN PROGRESS!
ReplyForward
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| Re: [GMCnet] Where did you put ur temp sensor for an electronic fan clutch? [message #352692 is a reply to message #352691] |
Tue, 10 March 2020 10:58  |
jhbridges
Messages: 8412
Registered: May 2011
Location: Braselton ga
Karma: -74
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Senior Member |
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The question becomes for the PWM controllers, what's the optimum repetition rate for pulses? I gather both extremes are being investigated. I lean toward the two seconds, but purely on instinct.
Also, how accurate is stuffing the sensor in the radiator fins vs in the hose?
Anybody using the tach output for anything?
--johnny
Foolish Carriage, 76 26' Eleganza(?) with beaucoup mods and add - ons.
Braselton, Ga.
I forgive them all, save those who hurt the dogs. They must answer to me in hell
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| Re: [GMCnet] Where did you put ur temp sensor for an electronic fan clutch? [message #352698 is a reply to message #352692] |
Tue, 10 March 2020 13:43 |
Hal StClair
Messages: 971
Registered: March 2013
Location: Rio Rancho NM
Karma: -12
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Senior Member |
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The PWM controller on mine (home brew electronic fan clutch setup) acts more as an on off switch as I'd guess the pulses are much too fast for the viscous valve in the clutch. The PWM controller was built for an electric fan so in it's intended application I'm sure it works correctly. If you have a method to slow down the pulses Johnny, I'd love to know how to do it. The OEM's manage it through their PCM's I'd imagine. Being able to ramp up the speed as temperature requires would be great. It would probably all but eliminate full on fan engagement and the accompanying noise.
As for sensor location, I used the radiator fins rather than direct H2O sensing. My research as well as the PWM's manufacture's suggestions recommend that location. I don't see an issue with either location as the activate temps are adjustable and can be easily set with a known good temperature gauge. Keeping the temps in check is what it's all about and with the T stat working correctly that should regulate the actual engine temps accordingly.
And the tach output wires are in free air just enjoying the ride.
Hal
"I enjoy talking to you. Your mind appeals to me. It resembles my own mind, except you happen to be insane."
1977 Royale 101348,
1977 Royale 101586, Diesel powered,
1974 Eagle Bus 45',w/slideout,
Rio Rancho, NM
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| Re: [GMCnet] Where did you put ur temp sensor for an electronic fan clutch? [message #352735 is a reply to message #352698] |
Thu, 12 March 2020 11:59 |
Keith V
Messages: 2337
Registered: March 2008
Location: Mounds View,MN
Karma: 0
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Senior Member |
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PWM rate is usually far above the response rate of whatever you are controlling. It is used as a simple way for a digital controller to supply an analog voltage. A low duty cycle looks like a low voltage while a high duty cycle looks like a high voltage. The fan or clutch or whatever is never expected to be able to cycle at the PWM frequency, rather the RMS voltage of the waveform looks like a variable DC voltage to the device being controlled,
Note that some devices, like most air solenoids do not work well with a PWM signal because they will do nothing until the voltage reaches the pull in voltage, upon which they will fully open and latch there until the voltage drops below the drop out voltage. There is voltage hysteresis that prevents rapid cycling between open and closed.
The fan clutch may work with PWM, but testing would have to be done. A variable power supply would suffice.
Just power the clutch and vary the voltage, see if the clutch engagement is dependent upon voltage or if there is a sudden change at a specific voltage
________________________________
From: Gmclist on behalf of Hal StClair via Gmclist
Sent: Tuesday, March 10, 2020 1:43 PM
To: gmclist@list.gmcnet.org
Cc: Hal StClair
Subject: Re: [GMCnet] Where did you put ur temp sensor for an electronic fan clutch?
The PWM controller on mine (home brew electronic fan clutch setup) acts more as an on off switch as I'd guess the pulses are much too fast for the
viscous valve in the clutch. The PWM controller was built for an electric fan so in it's intended application I'm sure it works correctly. If you have
a method to slow down the pulses Johnny, I'd love to know how to do it. The OEM's manage it through their PCM's I'd imagine. Being able to ramp up the
speed as temperature requires would be great. It would probably all but eliminate full on fan engagement and the accompanying noise.
As for sensor location, I used the radiator fins rather than direct H2O sensing. My research as well as the PWM's manufacture's suggestions recommend
that location. I don't see an issue with either location as the activate temps are adjustable and can be easily set with a known good temperature
gauge. Keeping the temps in check is what it's all about and with the T stat working correctly that should regulate the actual engine temps
accordingly.
And the tach output wires are in free air just enjoying the ride.
Hal
--
1977 Royale 101348,
1977 Royale 101586, Diesel powered,
1975 Eleganza II, 101230,
1974 Eagle Bus 45',w/slideout,
Rio Rancho, NM
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Keith Vasilakes
Mounds View. MN
75 ex Royale GMC
ask me about MicroLevel
Cell, 763-732-3419
My427v8@hotmail.com
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