cooling fan bypass

[barend]

Trying to hook in a bypass switch for the cooling fan before buttoning her back up. I've put a splice in both the black and blue wire going to the fan but am not sure which one to connect to ground and which one to the battery. Would I need a inline fuse and if so what size?

 

Thanks.

[Rocket]

Trying to hook in a bypass switch for the cooling fan before buttoning her back up. I've put a splice in both the black and blue wire going to the fan but am not sure which one to connect to ground and which one to the battery. Would I need a inline fuse and if so what size?

 

Thanks.

 

It is simpler than that, splice the wire by the spade connector at the temp switch (switch connects ground when hot enough) behind the right fairing. Connect the wire added to a switch & ground to other side of new switch, then it can be turned on at will, by flipping the switch, or let it operate normally.

 

[N3FOL]

I am not sure why you would like to bypass the cooling fan. Unless you are having heat issues thus causing your bike to run poor, I personally would not recommend doing this. Perhaps just replace sensors or thermostat at a regular basis and let the system work as it is intended to be.

[jasonm.]

I think he wants manual fan switch. DO NOT connect any +12 volts to the fan thermo-switch. The thermo switch is completing the ground side of the circuit. Thus you only need to run a ground wire to one side of the thermo-switch or the fan to make it run. Do you understand? Best if you have the service manual.

[rbjohnsn]

You would need to use an off switch plus a 10amp fuse to override the thermo switch. By adding the on / off switch inline with a 10 amp fuse to chassy ground would function as the thermo switch in the off position. Placing it on would activate the fan.

 

The fan's ground line is fused at 10 amps. If you don't use a fuse then the exisiting fuse would be out of the circuit.

[Guest tx2sturgis]

You can bypass the thermo switch, but keep in mind that if the fan is drawing say, 5 amps (maybe more), all the time, thats 5 amps you dont have for other accessories. It may be just enough current draw to slowly discharge the battery, if you are running say, high-wattage passing lites, and other goodies, when running in stop and go traffic.

 

But I can see a use for this, such as running up a long grade pulling a trailer in the summer heat. Just flip the fan on and dont worry about over heating.

 

[Rocket]

The fan's ground line is fused at 10 amps. If you don't use a fuse then the exisiting fuse would be out of the circuit.

 

This is 1st gen, not a 2nd gen & all fuses are on the power side, with these bikes (I haven't looked at 2nd gen wiring).............

 

The thermo switch is only a tempature controlled ground for the fan. Switch closed, ground circuit is completed & fan turns on. Switch opens, ground circuit is incomplete & fan turns off.

 

[a1bummer]

I just got done doing similar. I used a rear window defrost relay with timer so it only comes on for ten minutes. If I hit it again right away it comes on for another five. I just spliced it to the blue wire going to the fan. I also changed the thermostat and flushed out the old coolant and put in some new stuff and replaced my radiator cap. That alone made quite a bit of difference. The other day it was in the mid 80's and with the fan on it only went to just over midway on the gauge.

[camos]

Is the fan switch supposed to be in tight or will it normally be able to be turned by fingers? My fan isn't working so I'm thinking the fan switch is not properly installed.

 

Why is it you want a relay to bypass the fan circuit?

[twigg]

I have a 1st Gen.

 

Now I have thoroughly overhauled the cooling system I can't get the temp gauge above about one third into the green. This two up 75mph in 100F ambient.

 

It does rise when stationary, then the fan cuts in and it drops again.

 

So why are folk bypassing, or manually controlling the fan?

 

Am I missing something here?

[dingy]

Is the fan switch supposed to be in tight or will it normally be able to be turned by fingers? My fan isn't working so I'm thinking the fan switch is not properly installed.

 

Why is it you want a relay to bypass the fan circuit?

 

Not sure if this is what you are asking but here goes.

 

A stock setup does not have a fan switch, a switch that can be operated by the rider.

 

On the right front side is a 'Joint' yes that's the official name. It is a housing where the upper radiator hose, both hoses to the heads, a hose to the twinkie, all connect, and the two thermostats reside. One of these thermostats operates the temp. gauge, it is a variable resistance type of sensor.The other controls the fan, this one closes it's contact at a preset temperature to start the fan. If either of these two are loose, you should be leaking coolant. Picture attached of this housing.

 

Some riders are concerned about the indication on the temp gauge and have wanted to install a manual fan activation switch, there may be other reasons they have done this also.

 

Gary

[Yammy]

Easier than splicing, get a couple of solderless female disconnects with a piggyback male. Temp switch will run as normal but you can switch fan on manually with a switch from the two extra wires.

[camos]

A stock setup does not have a fan switch, a switch that can be operated by the rider.

I knew that but was wondering what the purpose of installing a manual switch was. Depending on how it is wired, a manual switch could turn on the fan before the sensor turned it on or the fan could be turned off after the sensor had turned it on. Or the sensor could be totally bypassed so the fan could be turned on whenever it was needed. There might be some benefit to being able to turn the fan on when you want it but it seems to me the automated switch should still be the best for all around usage.

One of these thermostats operates the temp. gauge, it is a variable resistance type of sensor.The other controls the fan, this one closes it's contact at a preset temperature to start the fan. If either of these two are loose, you should be leaking coolant. Picture attached of this housing.

My switch was loose but not leaking. I disconnected the wires and turned it until it stopped then reconnected the wires. Assume that was not the problem as after a ride I was messing with the lights again and it boiled over again. During the ride the temp gauge was sitting about 1/3 of the way up the gauge. Found the fan connection on the left side and cleaned it before going on the ride. Tomorrow I'll hook up the fan directly to the battery and see if it works.

[twigg]

I knew that but was wondering what the purpose of installing a manual switch was. Depending on how it is wired, a manual switch could turn on the fan before the sensor turned it on or the fan could be turned off after the sensor had turned it on. Or the sensor could be totally bypassed so the fan could be turned on whenever it was needed. There might be some benefit to being able to turn the fan on when you want it but it seems to me the automated switch should still be the best for all around usage.

[/size][/font] My switch was loose but not leaking. I disconnected the wires and turned it until it stopped then reconnected the wires. Assume that was not the problem as after a ride I was messing with the lights again and it boiled over again. During the ride the temp gauge was sitting about 1/3 of the way up the gauge. Found the fan connection on the left side and cleaned it before going on the ride. Tomorrow I'll hook up the fan directly to the battery and see if it works.

 

Try replacing the radiator cap.

 

If the cap is not holding the correct pressure, the system WILL boil over even if everything else is working perfectly well, and at a lower temperature that what is required to have the fan running.

 

What is happening is that the coolant, as the pressure rises, is forced back past a leaking (internally) cap, and into the coolant reservoir where it normally should not be.

 

This coolant is very hot, and it will cause the expansion chamber coolant to boil .... that sends coolant out of the overflow pipe and onto a hot engine.

 

Lots of steam and a puddle on the ground are the result.

 

Replacing the cap, assuming the head gasket is okay, should be a complete cure.

 

Ask me how I know

 

What is more, it will boil over even with the gauge registering a normal temperature.

[camos]

If I find the fan is working with a direct connection to the battery I will try a new cap as you suggest. I know there is a thread with several part numbers for aftermarket radiator caps. Finding a particular thread on this site might be the bigger challenge though.

 

Thanks for the suggestion Twigg.

[Kirby]

I put a bypass switch on my Vmax several years ago after getting caught in extremely slow moving traffic in Sevierville, TN . The temp needle would get right up to overheating then the fan would kick on and cool things down like it was supposed to do. It was just too close for comfort for me. All the time I'm thinking "What if it fails to come on?". This went on from Sevierville all the way to Gatlinburg. My friends Triumph was trying to overheat at the same time. All this in the 100 degree heat and traffic was moving about half a car length at a time and nowhere to get out of traffic. Anyway when I got back from that trip I put the bypass switch in. It allows you to turn on the fan and it will run continuously until you turn it off. When turned off it will cycle normally. It works great for me.

[twigg]

If I find the fan is working with a direct connection to the battery I will try a new cap as you suggest. I know there is a thread with several part numbers for aftermarket radiator caps. Finding a particular thread on this site might be the bigger challenge though.

 

Thanks for the suggestion Twigg.

 

It's Autozone CST 7513

 

I told you not to ask me how I know!!!

 

Oh, it's $6

[dingy]

The easiest way to wire in a bypass switch would be to do it at the thermostat switch itself. This is the larger brass body switch in my 1st post that red arrow pointing to connections. All you need to do is install a switch between the two wires going into this thermostat. This circuit already is protected by its own fuse. No need for a relay. From schematic these should be a one brown & and one blue wire. All the thermostat does is short these two wires together, a switch will do the same thing. I would not eliminate this thermostat from circuit.

 

To test the fan, turn key to on position, and connect a jumper between the two wires on this thermostat. The fan should start to run. If does not, then connect a jumper from the blue wire to the positive battery post. If it does run, then possibly a bad fuse. If it still doesn't run You can go to the two pin connector coming out of the fan itself. You will need to put two jumpers on this on, one positive & one negative, for a test and with connector apart, it doesn't matter on polarity to fan.

 

You said this switch was loose, but not leaking which is concerning. As mentioned earlier, a bad radiator cap could be possible, but another item would be a failed or bad condition water pump. Are you needing to add coolant to the system often? How full is the overflow bottle? Do you ever see coolant on ground under bike?

 

Gary

Edited July 3, 2011 by dingy
clarified jumper on thermostat

[twigg]

The easiest way to wire in a bypass switch would be to do it at the thermostat switch itself. This is the larger brass body switch in my 1st post that red arrow pointing to connections. All you need to do is install a switch between the two wires going into this thermostat. This circuit already is protected by its own fuse. No need for a relay. From schematic these should be a one brown & and one blue wire. All the thermostat does is short these two wires together, a switch will do the same thing. I would not eliminate this thermostat from circuit.

 

To test the fan, turn key to on position, and connect a jumper between the two terminals on this thermostat. The fan should start to run. If does not, then connect a jumper from the blue wire to the positive battery post. If it does run, then possibly a bad fuse. If it still doesn't run You can go to the two pin connector coming out of the fan itself. You will need to put two jumpers on this on, one positive & one negative, for a test and with connector apart, it doesn't matter on polarity to fan.

 

You said this switch was loose, but not leaking which is concerning. As mentioned earlier, a bad radiator cap could be possible, but another item would be a failed or bad condition water pump. Are you needing to add coolant to the system often? How full is the overflow bottle? Do you ever see coolant on ground under bike?

 

Gary

 

Every time I read your posts, Gary, I like them more You give solid advice.

 

I am going to add something about cooling systems that boil over ....

 

If you are experiencing coolant loss, then you need to find out where it is going. It can only go three places:

 

It can leak out of a bad joint. It can go out of the exhaust or into the sump if the head gasket is bad, or it can exit from the overflow on the expansion chamber. Oh, and it can get past the seal in the waterpump and mix with the oil (not good).

 

However, mine was overheating and NOT losing coolant, well not much anyway. All Joints were good, the headgasket was good and the water was not getting into the engine ... so where the f$%k was it going?

 

When I returned from a 30 mile run, in hot weather and high speed, I noticed, and could hear, the coolant in the expansion chamber boiling. This was accompanied by steam from the motor and a puddle on the floor.

 

For all the world it looked like the bike had boiled over in a spectacular way. The cooling fan was running just fine but the coolant was boiling, or appeared to be.

 

I found out that two things could cause this.

 

The first was a damaged head gasket. Common problem on over heated alloy heads. The second was a failed pressure cap. Guess which one I was praying for?

 

The coolant lowers the boiling point of water from the regular 212F. The motor runs at about 220F, or thereabouts. The radiator cap raises the boiling point of the coolant to around 265F, preventing boiling when the engine is running normally.

 

If the cap fails internally, then the boiling point drops and the coolant boils well below the temperature that the fan cuts in. This boiling fluid goes through the pressure cap release valve and up into the expansion chamber, where it boils the fluid there. That then spits out of the overflow onto the right side of the engine, drips on the floor and steams like a good 'un.

 

The same thing can happen if the head gasket is gone. In this case the combustion gasses over pressurize the system with the same result.

 

The shop can test the coolant for combustion residues, but a simpler test is to do a compression check. Also, the rad cap is a service item with a two year interval. The easiest test of all is to replace it and see if that fixes the problem.

 

It is well worth checking that the fan is working as described, but in normal riding the gauge should get nowhere near the temp. required to switch the fan on. In heavy traffic it will cycle repeatedly.

 

Honestly though .... In all these posts about cooling issues, and I have had ALL those issues with this bike, I cannot see a good reason for adding a switch to the fan circuit.

 

Depending on how you added one, there is the risk of either never having to use it (good) or using it too much and the engine running too cold (much less good).

 

just sayin'

[camos]

The easiest way to wire in a bypass switch would be to do it at the thermostat switch itself. This is the larger brass body switch in my 1st post that red arrow pointing to connections. All you need to do is install a switch between the two wires going into this thermostat. This circuit already is protected by its own fuse. No need for a relay. From schematic these should be a one brown & and one blue wire. All the thermostat does is short these two wires together, a switch will do the same thing. I would not eliminate this thermostat from circuit.

That does seem to be the best solution.

 

To test the fan, turn key to on position, and connect a jumper between the two wires on this thermostat. The fan should start to run. If does not, then connect a jumper from the blue wire to the positive battery post. If it does run, then possibly a bad fuse. If it still doesn't run You can go to the two pin connector coming out of the fan itself. You will need to put two jumpers on this on, one positive & one negative, for a test and with connector apart, it doesn't matter on polarity to fan.

Jumping between the blue and brown connectors gets nothing. Putting a pos from battery to the blue gets small sparks. Fan runs when connecting pos and neg from battery to connector on left side. Can you tell me where the fuse for the fan is located? It is not listed in the fuse panel with the ignition and headlights etc.

You said this switch was loose, but not leaking which is concerning. As mentioned earlier, a bad radiator cap could be possible, but another item would be a failed or bad condition water pump. Are you needing to add coolant to the system often? How full is the overflow bottle? Do you ever see coolant on ground under bike?

I have only ridden this bike for a few hours in total, most of which was yesterday. The bike has been run several times while in storage and no overheating or coolant puddles were noticed. The switch body was loose so I turned it until it stopped. After the first time it boiled I drained and flushed the cooling system but only filled with plain water just in case I had to pull the radiator to deal with the fan. Yesterday while riding the temp gauge stayed at 1/3 in the green and only got up to a bit below 1/2 when stopped for lights. I am just going to guess that would indicate the pump is working well enough. Also when the motor is operating pulsing can be seen in the black hose on the right side running from forward to about the middle of the engine so it appears coolant is circulating.

[twigg]

That does seem to be the best solution.

 

[/size][/font] [/size][/font]Jumping between the blue and brown connectors gets nothing. Putting a pos from battery to the blue gets small sparks. Fan runs when connecting pos and neg from battery to connector on left side. Can you tell me where the fuse for the fan is located? It is not listed in the fuse panel with the ignition and headlights etc.

I have only ridden this bike for a few hours in total, most of which was yesterday. The bike has been run several times while in storage and no overheating or coolant puddles were noticed. The switch body was loose so I turned it until it stopped. After the first time it boiled I drained and flushed the cooling system but only filled with plain water just in case I had to pull the radiator to deal with the fan. Yesterday while riding the temp gauge stayed at 1/3 in the green and only got up to a bit below 1/2 when stopped for lights. I am just going to guess that would indicate the pump is working well enough. Also when the motor is operating pulsing can be seen in the black hose on the right side running from forward to about the middle of the engine so it appears coolant is circulating.

 

Pretty much what I get.

 

The needle stays about at the 1/3rd position, the fan cuts in at just over 1/2 way up, and the fan sends the needle back down to 1/3rd before shutting off. Yours might not get hot enough .... Leave it running longer at standstill. If the needle gets to 3/4 and the fan is not on, there may be an issue with the fan. Don't let it get much higher than that, those cylinder heads don't like too much heat.

 

When I pulled the rad, one small hose was completely blocked, there was corrosion all over the place which is all now cleaned out.

 

I am still concerned about the boiling ..... It should not boil, not ever. Boiling suggests pressure issues of one kind or another.

[dingy]

[/size][/font] [/size][/font]Can you tell me where the fuse for the fan is located? It is not listed in the fuse panel with the ignition and headlights etc.

 

 

There is a second fuse block on the MKII bike. It has ATC style fuses. But, I don't know where it is at. I barely remember where stuff was supposed to be on my MKI, which doesn't have this fuse block. The fan fuse is in this 2nd block.

 

The pulsing you mention seeing in the hose is interesting. I don't know what would cause pulsing other than a blown head gasket. The water pump should be a smooth flow, no pulsing.

 

Gary

[twigg]

There is a second fuse block on the MKII bike. It has ATC style fuses. But, I don't know where it is at. I barely remember where stuff was supposed to be on my MKI, which doesn't have this fuse block. The fan fuse is in this 2nd block.

 

The pulsing you mention seeing in the hose is interesting. I don't know what would cause pulsing other than a blown head gasket. The water pump should be a smooth flow, no pulsing.

 

Gary

 

The second fuse block is ahead of the original, between the battery and the headstock.

 

It has four fuses that control the Hazards and the Audio system .... Unsure about the other two without looking it up.

[camos]

There is a second fuse block on the MKII bike. It has ATC style fuses. But, I don't know where it is at. I barely remember where stuff was supposed to be on my MKI, which doesn't have this fuse block. The fan fuse is in this 2nd block.

Eureka, you have got it, the fan fuse was blown. This ATC fuse block is just behind and to the right of the front holder tab for the top cover. It's interesting that there would be a mix of the ATC style and glass tube style fuses.

The pulsing you mention seeing in the hose is interesting. I don't know what would cause pulsing other than a blown head gasket. The water pump should be a smooth flow, no pulsing.

The hose in question is the one from the fan sensor to a block between the front and back cylinders. Perhaps pulsing is the wrong term. The hose kind of bobs up and down. This may just be an indication that the coolant level was low. Remember this bike has not been ridden for over a year and I had not gotten to checking the coolant level. Since it has boiled over, been drained and refilled with only water and the fan does work so I will not have to be removing the radiator... I will fill the system with antifreeze today. Perhaps that bobbing will then go away.

[dingy]

The good news is you know where the fuse is at, the bad news is something made it blow, and only the fan & thermostat is on this circuit, so you probably still have an issue.

 

The 'pulsing' could have been due to the low coolant level. The water pump may be at the point of just getting enough water to be effective, as soon as it pumps some water, then it runs out again till that water cycles back through radiator. This would happen rapidly, but could cause the pulsing.

 

Gary