Honda ATV Forum banner
1 - 10 of 10 Posts

·
Registered
Joined
·
4 Posts
Discussion Starter · #1 ·
I hope somebody can answer my question. I have a 2004 Foreman S in my shop. Original complaint: fan doesn't come on and no temp light but seems to be getting really hot. I replaced the temp switch and the fan works but at the same time the light comes on. When the fan quites the light goes out. Customer says this has never operated this way before. I called the Honda dealer and they told me it is working fine. The customer insist it is not. That before the fan would come on and not the light. So I replaced the fan control unit, same thing: fan comes on so does the light, fan goes out so does the light. So is this the way it is supposed to operate?
 

·
Premium Member
Joined
·
38,619 Posts
oil temp light will come on for two reasons ?, low on oil, which would cause it to get to hot ?, or..the fan does not come on before the oil gets to hot. I've never seen any of my oil temp lights come on ?, mostly because the fans work the way they should. the oil temp light is controlled by the oil temp sensor, sooo..I would make sure you installed the correct oil temp sensor for starters ?. check the wire leading to the switch, you may have a short between the light and ground ?. I don't own a '04 model, mine is a '03 trx450fm foreman. I also own a '89 trx350D foreman, and my oil temp light on both has never came on before the fan kicks in.
 

·
Registered
Joined
·
4 Posts
Discussion Starter · #3 ·
Thanks for the reply Shadetree. Can you explain to me how the system works? It only has the one temp sensor that triggers the fan control unit, correct? Is this supposed to be a variable temp sensor? If I ground the wire to the sensor both fan and light come on. So in my mind, it would have to act like a potentiometer to vary the amount of ground. Some ground triggers the fan, complete ground the light also comes on. Is this correct? Or am I completely off base? Thanks for any and all help.
 

·
Premium Member
Joined
·
38,619 Posts
Thanks for the reply Shadetree. Can you explain to me how the system works? It only has the one temp sensor that triggers the fan control unit, correct? Is this supposed to be a variable temp sensor? If I ground the wire to the sensor both fan and light come on. So in my mind, it would have to act like a potentiometer to vary the amount of ground. Some ground triggers the fan, complete ground the light also comes on. Is this correct? Or am I completely off base? Thanks for any and all help.
you are very correct !. when the sensor detects a oil over heat ?, it acts like a ground, turning the oil temp light on, and then the fan control unit turns the fan on. in my years of working on, riding atvs, I have always seen and heard the fan come on, never seen the light come on. soooo..this tells me your oil temp sensor is not right.
 

·
Premium Member
Joined
·
38,619 Posts
Could your problem be #11 (thermostat) on this print , it is hidden under the front fender on the right hand side of my 2002 TRX450 , it is sealed in a clear plastic bag and looks like a watch battery , what it does is beyond me

Honda ATV Parts 2002 TRX450FM A WIRE HARNESS (TRX450FM) Diagram
you ask a very good question fish ^^^. I think that part controls the fuel injection on fuel injected carbs ?, I am not sure on this ?, but I will ask my bud at the Honda dealership, he's my master in mechanics on atvs..lol. I do know it checks the surrounding air temp. just not sure why ??.
 

·
Registered
Joined
·
4 Posts
Discussion Starter · #7 ·
Once again, thanks for the replies. The thermostat by the fender, I have learned, controls the carb heater. From what I can see in the wiring diagram, it has nothing to do with the fan. I have been reading the service manual, and from what I can tell the oil temp sensor is supposed to be variable. At 302F it is supposed to have 306-340 ohms and at 338F it is supposed to drop to 209-231 ohms. In my thinking that means it will trigger the fan first and then if it continues to get hotter it will turn on the light? I am going to test this today sometime, hopefully find out more. If anybody has any more ideas, I will take them.
 

·
Premium Member
Joined
·
12,683 Posts
RKB,
my 450 is a 2002 and I have looked at the fan circuit wiring diagram a few times , there are 2 wires coming off the thermo switch and you are right one wire goes to the carb heater , the other wire goes to the fan control unit
 

Attachments

·
Registered
Joined
·
4 Posts
Discussion Starter · #9 ·
Correct me if I am wrong, but I think the wire that goes both to the fan control box and the thermo switch comes from the "light" fuse in the fuse box. Therefore I thought that was the power in wire.
 

·
Premium Member
Joined
·
12,683 Posts
I don't know much about the fan circuit but would like too , as here's a pic of my thermo switch --------

You have a 350 or a 450 , I have heard the 2002 TRX450FM and the 2004 TRX450S are the same bike , I know that wiring diagram I posted is suppose to be for a 1998- 2004 450
 

Attachments

1 - 10 of 10 Posts
This is an older thread, you may not receive a response, and could be reviving an old thread. Please consider creating a new thread.
Top