Wiring a 4 wire fan into a two wire
Discussion
I'm replacing an old rad fan with a new Spal one. The old had four wires to it (3 speed), new one has just two wires.
I think i've worked out where to put the black -tve one
Whilst it does have these 4 present this model might not use them all as it has no air-con, but I don't know.
Can I put all 3 +tve together? If not, how should I wire it do you think?
I think i've worked out where to put the black -tve one
Whilst it does have these 4 present this model might not use them all as it has no air-con, but I don't know.
Can I put all 3 +tve together? If not, how should I wire it do you think?
Looks as if your original fan has two switched positive supplies, one switched ground and one permanent ground.
I'm not familiar with that type of fan controller but I guess these relays are switched at different temperatures to bring the fan in gradually using different combinations of windings.
If the car is still running, you could monitor the engine temperature with the fan disconnected to see which order the relays are switched and at what temperatures. If one of the temperatures matches the temperature you want your fan to come in at, you could use that relay to operate the new fan.
Or just add an independent fan controller if that is all looking like too much hassle.
I'm not familiar with that type of fan controller but I guess these relays are switched at different temperatures to bring the fan in gradually using different combinations of windings.
If the car is still running, you could monitor the engine temperature with the fan disconnected to see which order the relays are switched and at what temperatures. If one of the temperatures matches the temperature you want your fan to come in at, you could use that relay to operate the new fan.
Or just add an independent fan controller if that is all looking like too much hassle.
Penelope Stopit said:
What car is it and would you like to have 1, 2 or 3 speeds, the job is easy once you've decided what you want
I can't imagine why it would matter, but it's a Mazda MX-5.If I could keep it as it is with the fan speeds it would be great, as said earlier it's a non air-con model so some of the speeds may be redundant, but I don't know.
Being designed for air con would explain one of the supplies.
Do you know for sure that the original fan was actually a variable speed fan? The only way to achieve that with a two wire fan is using big resistors or a PCM controller, and I'd suggest neither of those are worth the bother for an engine cooling fan.
Do you know for sure that the original fan was actually a variable speed fan? The only way to achieve that with a two wire fan is using big resistors or a PCM controller, and I'd suggest neither of those are worth the bother for an engine cooling fan.
GreenV8S said:
Does the original fan system turn the fan on with the air conditioning even when the engine is cool? That would explain one of the supplies.
Do you know for sure that the original fan was actually a variable speed fan? The only way to achieve that with a two wire fan is using big resistors or a PCM controller, and I'd suggest neither of those are worth the bother for an engine cooling fan.
It doesn't have air-con.Do you know for sure that the original fan was actually a variable speed fan? The only way to achieve that with a two wire fan is using big resistors or a PCM controller, and I'd suggest neither of those are worth the bother for an engine cooling fan.
No I don't know for certain if it was variable speed, I only got told it was and i'm usually in the car driving it so have no idea. It's also too cold at the moment to test much, I left it idling for half an hr and the fan never kicks in. The only way to test it practically would be to put the old fan back on and a brick on the accelerator for a while and leave it.
227bhp said:
Penelope Stopit said:
What car is it and would you like to have 1, 2 or 3 speeds, the job is easy once you've decided what you want
I can't imagine why it would matter, but it's a Mazda MX-5.If I could keep it as it is with the fan speeds it would be great, as said earlier it's a non air-con model so some of the speeds may be redundant, but I don't know.
Ok, it's not a variable speed motor, the motor in the diagram you've posted is controlled by brush position in the same way as a wiper motor is and although the diagram shows the brushes at 90 degrees to eachother this doesn't mean that they are at 90 degrees to eachother, the angles between the brushes could be anything including 90 degrees and there is no way of finding out without splitting the motor
You can use the 13, 19 and 20 negative inputs as long as you run the engine up to temperature and determine that they are all switching ok and what order they are switching in
The rest is easy, fit and wire a three speed rad fan resistor in series with the relays once you have proven the switching order
Penelope Stopit said:
227bhp said:
Penelope Stopit said:
What car is it and would you like to have 1, 2 or 3 speeds, the job is easy once you've decided what you want
I can't imagine why it would matter, but it's a Mazda MX-5.If I could keep it as it is with the fan speeds it would be great, as said earlier it's a non air-con model so some of the speeds may be redundant, but I don't know.
Ok, it's not a variable speed motor, the motor in the diagram you've posted is controlled by brush position in the same way as a wiper motor is and although the diagram shows the brushes at 90 degrees to eachother this doesn't mean that they are at 90 degrees to eachother, the angles between the brushes could be anything including 90 degrees and there is no way of finding out without splitting the motor
You can use the 13, 19 and 20 negative inputs as long as you run the engine up to temperature and determine that they are all switching ok and what order they are switching in
The rest is easy, fit and wire a three speed rad fan resistor in series with the relays once you have proven the switching order
A.
Take car out get it warm. Back in workshop with brick on accelerator, plug in old fan and lay it on top.
I'm going to snip red and blue and join them back together temporarily.
When fan kicks in i'll pull red or blue apart and see if the fan stops.
Perhaps then (but dangerous) I could do:
B.
Plug it back in and let it get hotter, see if fan operates at higher speed then pull apart other wire if it does.
Will a three speed fan resistor be defined by having 3 pins on it?
I think I now understand the situation you are in
Earlier I had guessed that you were replacing the 4 brush motor because it was siezed or burnt out
Am I correct in now thinking that there could be nothing wrong with the motor and you are about to test it to find out
If you are about to test the motor you could do so with it off the car on a bench
A simple way for you to test the motor would be to connect a permanent negative to that brush that is permanent neg in the diagram and connect a 20amp fused positive 1st to the brush that the red cable connects to and 2nd come off the red and connect the fused pos to the blue which should give you a faster speed
If the above check ok you can then remove the permanent negative from the brush and connect it to the brush that the green normally connects to and connect the 20amp fused positive to where the blue normally connects to which may well give you a speed similar to that in the above (black neg/red pos) 1st test
The above is easier and better than cutting cables and will prove if all the brushes are ok
If all the above give good results you can now connect it up to the car and test the rest of the circuit
Bear in mind that due to relay 3 switching a negative to a brush, relay 1 or 2 need to be switching a positive to a brush at the same time so as to give a 3rd speed
Then there is always the job that catches us out, we often assume that relay fan 1 is for 1st speed, relay fan 2 for 2nd and 3 for 3rd, only later do we find out that it was nothing of the sort and the manufacturer simply numbered them that way
Earlier I had guessed that you were replacing the 4 brush motor because it was siezed or burnt out
Am I correct in now thinking that there could be nothing wrong with the motor and you are about to test it to find out
If you are about to test the motor you could do so with it off the car on a bench
A simple way for you to test the motor would be to connect a permanent negative to that brush that is permanent neg in the diagram and connect a 20amp fused positive 1st to the brush that the red cable connects to and 2nd come off the red and connect the fused pos to the blue which should give you a faster speed
If the above check ok you can then remove the permanent negative from the brush and connect it to the brush that the green normally connects to and connect the 20amp fused positive to where the blue normally connects to which may well give you a speed similar to that in the above (black neg/red pos) 1st test
The above is easier and better than cutting cables and will prove if all the brushes are ok
If all the above give good results you can now connect it up to the car and test the rest of the circuit
Bear in mind that due to relay 3 switching a negative to a brush, relay 1 or 2 need to be switching a positive to a brush at the same time so as to give a 3rd speed
Then there is always the job that catches us out, we often assume that relay fan 1 is for 1st speed, relay fan 2 for 2nd and 3 for 3rd, only later do we find out that it was nothing of the sort and the manufacturer simply numbered them that way
Edited by Penelope Stopit on Thursday 14th March 20:18
I've just spotted a problem that may crop up
If your car needs that very fast speed that the original motor could produce and you are going to be using a standard 2 brush motor to replace it, that 2 brush motor needs to be capable of rotating at a similar full speed and you could then use a 3 terminal resistor to gain 2 slower speeds
You would need to get hold of the RPM specs of both motors
If you are living in a coldish country you will very likely get away with a slow and full speed set-up using a standard 2 brush motor but bear in mind this is my opinion
If your car needs that very fast speed that the original motor could produce and you are going to be using a standard 2 brush motor to replace it, that 2 brush motor needs to be capable of rotating at a similar full speed and you could then use a 3 terminal resistor to gain 2 slower speeds
You would need to get hold of the RPM specs of both motors
If you are living in a coldish country you will very likely get away with a slow and full speed set-up using a standard 2 brush motor but bear in mind this is my opinion
Edited by Penelope Stopit on Thursday 14th March 20:38
Penelope Stopit said:
I think I now understand the situation you are in
Earlier I had guessed that you were replacing the 4 brush motor because it was siezed or burnt out
Am I correct in now thinking that there could be nothing wrong with the motor and you are about to test it to find out
If you are about to test the motor you could do so with it off the car on a bench
A simple way for you to test the motor would be to connect a permanent negative to that brush that is permanent neg in the diagram and connect a 20amp fused positive 1st to the brush that the red cable connects to and 2nd come off the red and connect the fused pos to the blue which should give you a faster speed
If the above check ok you can then remove the permanent negative from the brush and connect it to the brush that the green normally connects to and connect the 20amp fused positive to where the blue normally connects to which may well give you a speed similar to that in the above (black neg/red pos) 1st test
The above is easier and better than cutting cables and will prove if all the brushes are ok
If all the above give good results you can now connect it up to the car and test the rest of the circuit
Bear in mind that due to relay 3 switching a negative to a brush, relay 1 or 2 need to be switching a positive to a brush at the same time so as to give a 3rd speed
Then there is always the job that catches us out, we often assume that relay fan 1 is for 1st speed, relay fan 2 for 2nd and 3 for 3rd, only later do we find out that it was nothing of the sort and the manufacturer simply numbered them that way
Do I don't need to test the old fan to check it works? I want to put it in the bin.Earlier I had guessed that you were replacing the 4 brush motor because it was siezed or burnt out
Am I correct in now thinking that there could be nothing wrong with the motor and you are about to test it to find out
If you are about to test the motor you could do so with it off the car on a bench
A simple way for you to test the motor would be to connect a permanent negative to that brush that is permanent neg in the diagram and connect a 20amp fused positive 1st to the brush that the red cable connects to and 2nd come off the red and connect the fused pos to the blue which should give you a faster speed
If the above check ok you can then remove the permanent negative from the brush and connect it to the brush that the green normally connects to and connect the 20amp fused positive to where the blue normally connects to which may well give you a speed similar to that in the above (black neg/red pos) 1st test
The above is easier and better than cutting cables and will prove if all the brushes are ok
If all the above give good results you can now connect it up to the car and test the rest of the circuit
Bear in mind that due to relay 3 switching a negative to a brush, relay 1 or 2 need to be switching a positive to a brush at the same time so as to give a 3rd speed
Then there is always the job that catches us out, we often assume that relay fan 1 is for 1st speed, relay fan 2 for 2nd and 3 for 3rd, only later do we find out that it was nothing of the sort and the manufacturer simply numbered them that way
Edited by Penelope Stopit on Thursday 14th March 20:18
Or on Ebay. (some would say they are similar things).
I just want to know how to wire the new one up.
227bhp said:
Do I don't need to test the old fan to check it works? I want to put it in the bin.
Or on Ebay. (some would say they are similar things).
I just want to know how to wire the new one up.
You did post that that's what you were going to doOr on Ebay. (some would say they are similar things).
I just want to know how to wire the new one up.
227bhp said:
Ok here is what I propose:
A.
Take car out get it warm. Back in workshop with brick on accelerator, plug in old fan and lay it on top.
I'm going to snip red and blue and join them back together temporarily.
When fan kicks in i'll pull red or blue apart and see if the fan stops.
Perhaps then (but dangerous) I could do:
B.
Plug it back in and let it get hotter, see if fan operates at higher speed then pull apart other wire if it does.
Will a three speed fan resistor be defined by having 3 pins on it?
A.
Take car out get it warm. Back in workshop with brick on accelerator, plug in old fan and lay it on top.
I'm going to snip red and blue and join them back together temporarily.
When fan kicks in i'll pull red or blue apart and see if the fan stops.
Perhaps then (but dangerous) I could do:
B.
Plug it back in and let it get hotter, see if fan operates at higher speed then pull apart other wire if it does.
Will a three speed fan resistor be defined by having 3 pins on it?
Penelope Stopit said:
227bhp said:
Do I don't need to test the old fan to check it works? I want to put it in the bin.
Or on Ebay. (some would say they are similar things).
I just want to know how to wire the new one up.
You did post that that's what you were going to doOr on Ebay. (some would say they are similar things).
I just want to know how to wire the new one up.
227bhp said:
Ok here is what I propose:
A.
Take car out get it warm. Back in workshop with brick on accelerator, plug in old fan and lay it on top.
I'm going to snip red and blue and join them back together temporarily.
When fan kicks in i'll pull red or blue apart and see if the fan stops.
Perhaps then (but dangerous) I could do:
B.
Plug it back in and let it get hotter, see if fan operates at higher speed then pull apart other wire if it does.
Will a three speed fan resistor be defined by having 3 pins on it?
A.
Take car out get it warm. Back in workshop with brick on accelerator, plug in old fan and lay it on top.
I'm going to snip red and blue and join them back together temporarily.
When fan kicks in i'll pull red or blue apart and see if the fan stops.
Perhaps then (but dangerous) I could do:
B.
Plug it back in and let it get hotter, see if fan operates at higher speed then pull apart other wire if it does.
Will a three speed fan resistor be defined by having 3 pins on it?
227bhp said:
Do we need to know what the old fan was doing in order to wire the new one up?
No, but you will need to know if the control is switching negatives to the relays as I have mentioned above and there's the question mark against fan speed, you know more about what's needed than I doI take it you know that you could do away with the whole circuit and fit an adapter pipe that will take a 2 stage switch in the top hose and wire that switch to a couple of relays and a 2 speed resistor
Penelope Stopit said:
227bhp said:
Do we need to know what the old fan was doing in order to wire the new one up?
No, but you will need to know if the control is switching negatives to the relays as I have mentioned above and there's the question mark against fan speed, you know more about what's needed than I doI take it you know that you could do away with the whole circuit and fit an adapter pipe that will take a 2 stage switch in the top hose and wire that switch to a couple of relays and a 2 speed resistor
I had to explore that possibility first, but it seems no-one has a straight answer.
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