• Welcome to our site! Electro Tech is an online community (with over 170,000 members) who enjoy talking about and building electronic circuits, projects and gadgets. To participate you need to register. Registration is free. Click here to register now.

Bypass ECU :: Radiator Fan Control Switch

Status
Not open for further replies.

pradoartz

Member
Hi Friends,
I got an Yamaha r15v2 motorcycle. In my motorcycle the ECU got some problem in it. The radiator fan doesn't works automatically. So i made a ON/OFF button to control my radiator fan manually.

rad.jpg

But my question is how to make it automatically without changing the ECU(its too cost man)?

I got a coolant temperature sensor, which gives me the output as ohms Ω. When my coolant temp sensor gives 310 ohms as output, automatically the ECU gets the signal and switches ON the radiator fan relay.

coolant temp sensor.png cooltempsens006.gif

My question is how to use the coolant temp sensor to switch the radiator realy ON/OFF automatically without the ECU.
I am very much interested in DIY stuffs.

Please help me guys.
Thanks.
 
Last edited:

cowboybob

Well-Known Member
Most Helpful Member
Welcome to ETO, pradoartz!

Your coolant temperature sensor, in series with the appropriate fixed resistor, could be used as a "voltage divider" to provide a signal to a simple comparator (like an LM111). The LM111's output could drive a small relay that could then control the radiator fan motor.

Is this what you had in mind? And, if I may ask, how comfortable are you constructing small electronic circuits?

<EDIT> Hysteresis is also a consideration. With that in mind, the LM111 might not be the best comparator choice. I'm looking into that.
 
Last edited:

pradoartz

Member
Hi cowboybob. Thanks for the welcome message :)

To be frank, i have done only very small DIY electronic projects, like amplifier using LM386N and some small stuffs like that. I don't have any idea about micro-controllers or programming micro-controllers like that. So is there any simple circuits to get my project done. Thanks
 

pradoartz

Member
Also have you seen the last image i attached. In that you can see the resistance varies from 20KΩ to 0.1KΩ. My question is to exactly switch on my radiator relay by 0.3KΩ.

Thanks
 

alec_t

Well-Known Member
Most Helpful Member
The comparator circuit should have some hysteresis (i.e. a change of several degrees, rather than a fraction of a degree, would be needed to make it switch), otherwise the fan will be on/off/on/off continuously.... like a tart's drawers :D.
 

pradoartz

Member
Maybe a 555 timer would be better!!

Thanks Ian Rogers for the video. I got only some basic knowledge in electronics but i can built it if i get some exact circuit for what i am looking for. So can u make this 555IC to make a circuit for my exact need.

If the resistance below 310Ω, nothing should happen with the relay. If the resistance goes above 310Ω the relay should be switched on. Can You make a circuit using 555 friend.
 
Last edited:

spec

Well-Known Member
Most Helpful Member
Hi pradoartz,

I see you are from India. Care to tell us which part and put it next to 'Location' on your user page so that it shows in the window at the left of your posts.

I have some sympathy with you about your fan failing. I had the same thing on my automobile when 200 miles away from home. Cost me a small fortune to have the automobile towed back home. The problem turned out to be a faulty fan motor and a sticky relay.

I suspect that there will be a relay from the ECU that turns the fan motor on and off.

Can you check:

(1) The relay for correct operation
(2) The wiring for corrosion breaks
(3) The connectors for tight fit and corrosion.

Failing that, a simple circuit will bypass the ECU as the other members have already stated.

spec

By the way nice informative opening post- wish we had more like that.:cool:
 
Last edited:

Ian Rogers

User Extraordinaire
Forum Supporter
Most Helpful Member
In a 555 timer the threshold is normally 2 thirds Vcc.. As you need to switch at 300 ohm, I would use a 10k pot for the other resistor... Then drive a little relay from the 555 output... The fan will consume quite a bit of current!!
 

pradoartz

Member
Hi pradoartz,

I see you are from India. Care to tell us which part and put it next to 'Location' on your user page so that it shows in the window at the left of your posts.

I have some sympathy with you about your fan failing. I had the same thing on my automobile when 200 miles away from home. Cost me a small fortune to have the automobile towed back home. The problem turned out to be a faulty fan motor and a sticky relay.

I suspect that there will be a relay from the ECU that turns the fan motor on and off.

Can you check:

(1) The relay for correct operation
(2) The wiring for corrosion breaks
(3) The connectors for tight fit and corrosion.

Failing that, a simple circuit will bypass the ECU as the other members have already stated.

spec

By the way nice informative opening post- wish we had more like that.:cool:
The relay is fine
Wiring is also fine

From service center they advice to change the ECU. Me to got some doubts and changed the ECU with my friends bike. The radiator fan works well. The problem in my ECU is the radiator fan is spinning every time, like if i switch off the ignition key also its spinning which in turn draind my battery. my bike is totally depends by the battery since its a fuel injection model. Thanks
 

spec

Well-Known Member
Most Helpful Member
Also!!! Using a CMOS 555 on an automotive design may fair better..
Hi Ian,

You may be better off with the normal LM555 because it has twice the sink and source current of the LMC555 to drive the relay.

spec
 

pradoartz

Member
Yes, that circuit is fine, but change the 741 for an LM358.

The LM358 has two operational amplifiers in one case. Don't use the spare operational amplifier but connect the - pin to the output and connect the + input pin to 0V (ground).

spec

http://www.ti.com/lit/ds/symlink/lm158-n.pdf
sorry bro. I just googled it and i got that circuit. I don't have any idea about the circuit. Please can u make a circuit for me using 741.

sorry for too dumb.
 

spec

Well-Known Member
Most Helpful Member
The relay is fine
Wiring is also fine

From service center they advice to change the ECU. Me to got some doubts and changed the ECU with my friends bike. The radiator fan works well. The problem in my ECU is the radiator fan is spinning every time, like if i switch off the ignition key also its spinning which in turn draind my battery. my bike is totally depends by the battery since its a fuel injection model. Thanks
Got it. :)

Do you plan to remove the relay connection from the ECU and feed it with your substitute bypass circuit? Or would you use a different relay?

spec
 
Last edited:

spec

Well-Known Member
Most Helpful Member
sorry bro. I just googled it and i got that circuit. I don't have any idea about the circuit. Please can u make a circuit for me using 741.

sorry for too dumb.
Not dumb.

I will sort a circuit for you to consider in addition to the circuits already proposed.

But can you give an answer to the question about the relay in post #17 above.

spec
 
Last edited:

pradoartz

Member
Not dumb.

I will sort a circuit for you to consider in addition to the circuits already proposed.

But can you give an answer to the question about the relay in post #17 above.

spec
Yeah, i am planning to remove the relay connection from the ECU and i am going for the new circuit with new relay for my radiator fan. I will get the input from the coolant temperature sensor, which is already in my bike. And according to the service manual the radiator fan starts if the resistance from the temperature sensor is EQUAL to or LESSER than 326 ohms.

Exactly by 80 degree Celsius, the thermostat in my motorcycle opens the gate for the coolant present in the radiator, until that heat(80 degrees) the coolant which is inside the water pump will cool down the engine which in turns there is no need for radiator fan. So at 80 degrees the thermostat opens the gateway for the radiator coolant and it needs to switch ON the radiator fan. So the temperature sensor will get the resistance of 326 Ohms exactly by 80 degree Celsius. So i need to get a circuit to operate the radiator fan exactly by 80 degrees and above. Since the engine heat gets higher and higher the resistance from the temperature sensor gets lower. so have to design the circuit switches ON the relay if the resistance is EQUAL to or getting BELOW 326 Ohms.

Thanks
 
Last edited:

spec

Well-Known Member
Most Helpful Member
Hi pradoartz, I do not fully understand what you are planning on doing.

Let me explain: In order to design a circuit to replace the ECU fan control it is necessary to know what the replacement circuit will be driving, so that a correct design can be made.

Can I advise that you remove the ECU connection from the contact on the fan relay and connect the new circuit to the same contact on the fan relay. That will make the deign simpler.

If you agree with this approach I will need to know how the ECU drives the relay;
(1) is one end of the relay coil connected to 0V and does the ECU output a high voltage to operate the relay or
(2) is one end of the relay coil connected to 12V and does the ECU output a low voltage to operate the relay

I will also need to know what the relay coil resistance is (you can measure this with a multimeter).

if you have trouble understanding what I am asking please ask.

In general terms do you have access to electronic part suppliers and could you assemble a simple circuit.

Do you have:
soldering iron
solder
small pliers
small wire cutters
small screw driver
multimeter

Apologies for all the questions but the answers are required to make a sucess of this project.

spec
 
Status
Not open for further replies.

Latest threads

EE World Online Articles

Loading
Top