M3 Electric fan probs

[Fushion_Julz]

Looking for some pointers, here...

My M3 had (when purchased a short while back) a non-working slow speed on the cooling fan.

The fast speed worked OK so I checked the relay (OK) and replaced the fuse, even though that was OK, too...
Replaced the resistor on the front of the fan (bought from Coopers in Reading by chassis number) although, on inspection, the new item was a finned, metal case 0.5ohm 85W job...The one fitted (but seriously broken) was a ceramic body affair...Couldn't tell the ohm/watt rating as it was almost shattered beyond recognition!
I also repaired a burnt track in the fuse box and the slow speed fan now works (as does the hi-speed, too)....

But it works ALL the time the ignition is in position 3 (dash lights on)

Has anyone any ideas as to why?
Is it possible, for example, that the resistor type is that important (can't see it myself)...

Cheers in advance...

[ian332isport]

Welcome to the Zone

The resistor type will not make any difference. Some cars came fitted with the Ceramic Bosch resistor, and some came with the finned metal Magna resistor. They both perform the same function. If you have the low speed, then the resistor is doing it's job.

If the fan is on low speed all the time, I would check the radiator temp switch is not shorted (or possibly had a wire fitted in the connector to force the fan to run all the time).

Here is the circuit diagram for the cooling fan.



Ian.

[Fushion_Julz]

Cheers, Ian

I'll have a check, but TBH, the last owner is known to me (via MJF engineering who is my mate) nad she had the temp sensor replaced around Jan time...

Still worth looking, though and thanks for the diag...well useful



Only I notice that the resistor is marked as 6ohms....The one I got from the dealer is deffo a 0.5ohm 85w finned type...

[ian332isport]

Only I notice that the resistor is marked as 6ohms....The one I got from the dealer is deffo a 0.5ohm 85w finned type...

Yeah, that's a typo on the diagram. Had me wondering for a while as well. I'm also using the 0.5ohm finned type.

If you already found burnt tracks in the Fuse box, I guess you may have other issues, but the diagram should help trace the problem.

Cheers,

Ian.

[Demlotcrew]

Ian could you explain how the low speed works? Is it just a matter of sending +12 to the low speed pin on the fan?

A

[ian332isport]

Ian could you explain how the low speed works? Is it just a matter of sending +12 to the low speed pin on the fan?

A

Andrew,

The fan itself only has two connections (+ve and GND). For full speed operation, the fan sees the full 12v, and the fan is able to draw all the current it needs to spin at full speed. The only current limit in this circuit is the resistance of the wire etc.

For low speed operation, the +ve fan connection goes through the resistor which effectively limit's the current available to spin the fan. With limited current flow, the fan cannot spin at full speed, and therefore gives the low speed operation.

On the E36, this is done in a different way, and there are three connections on the fan. I beleive there is a high speed winding and a low speed winding in the motor. This is inherantly more reliable, and doesn't suffer from burnt out resistors (which get quite hot in operation).

Cheers,

Ian.

[Demlotcrew]

I see, but what im wondering is when the fan is on high speed, will the fan also need to have a +12v to the low speed pins? As the fan i have ( ) has a plug with three pins.

A

[Davenotouring]

I see, but what im wondering is when the fan is on high speed, will the fan also need to have a +12v to the low speed pins? As the fan i have ( ) has a plug with three pins.

A

Are you fitting an M3 fan to your iS now?

Why not just buy an M3 engine!!

[Demlotcrew]

I understand that the electrical motor on has positive and negative only

[Demlotcrew]

I see, but what im wondering is when the fan is on high speed, will the fan also need to have a +12v to the low speed pins? As the fan i have ( ) has a plug with three pins.

A

Are you fitting an M3 fan to your iS now?

Why not just buy an M3 engine!!

Well the fan i have is really noisy as some people have pointed out. So i have found a M3 one with all the brakets second hand cheap, im going to try and install that with all the correct wiring in the fuse box!

A

[Davenotouring]

That's fairy nuff.

I wouldn't mind fitting an M5 fan to mine.

[Demlotcrew]

That's fairy nuff.

I wouldn't mind fitting an M5 fan to mine.

Im sure we could manage to get that to fit! Ask Karan on hows hes going about the M5 fan install. With all that old man sunday driving you do up hill you need good cooling.

A

[Davenotouring]

Especially with my caravan on the back.

[ian332isport]

I see, but what im wondering is when the fan is on high speed, will the fan also need to have a +12v to the low speed pins? As the fan i have ( ) has a plug with three pins.

A

Andrew,

The the fan motor itself only has two connections. The reason you have three pins on the connector is because the resistor is mounted on the fan frame, so you have connections for low speed, high speed and GND.

You only need to give 12v to either the low speed OR the high speed connection. You never need power to both, but it would do no harm if you did.

Ian.

[Demlotcrew]

Thanks mate, i have looked at the electrics, now all i need to do if find the female three pin connector, any thoughts?

A

[ian332isport]

Thanks mate, i have looked at the electrics, now all i need to do if find the female three pin connector, any thoughts?

A

Andrew,

I have searched extensively in the ETK, but have never been able to find the female half of this connector.

It's possible that I may have something that will work though. I have an old A/C compressor that uses the same plug. It's possible this could be fitted on a wiring harness, but I would need to check.

I'll have a look tomorrow and let you know.

Cheers,

Ian.

[Demlotcrew]

Thanks mate, if it comes to it ill just need to cut the wires, but i would rather keep it stock! Im a sucker for neat wires!

A

[jpboost]

The connector comes apart. You buy each of the female 'pin' with a few inches of wire, Then get a housing to hold them in. I bought replacement wire/pins a few days ago and will just refit in the original housing.

I can try to dig out the p/n if you like.

BTW the M3 fan is not quiet!! especially not on high speed.

[ian332isport]

The connector comes apart. You buy each of the female 'pin' with a few inches of wire, Then get a housing to hold them in. I bought replacement wire/pins a few days ago and will just refit in the original housing.

I can try to dig out the p/n if you like.

BTW the M3 fan is not quiet!! especially not on high speed.

Yeah, the pins are easy enough to get, it's the female side of the plastic housing that you can't get (you can get the male half).

Ian.

[ian332isport]

Im a sucker for neat wires!

You and me both...

[ian332isport]

Thanks mate, if it comes to it ill just need to cut the wires, but i would rather keep it stock! Im a sucker for neat wires!

A

Andrew,

You're in luck

I had a look at my old A/C compressor, and it does have the female socket you require. I have given it a good clean, and it's as good as new.

It obviously doesn't have the electrical connections, but these are available from the dealer under this part number:

61 13 0 007 444

The only slight problem with the above connector pin, is that it won't have a wire quite as fat as the E30 fan wiring (4mm), it only has 2.5mm. I have searched through various models, and none list this connector with a fatter wire.

As long as you keep the length of the thinner wire as short as possible, then you should be okay. Modern wire is designed to carry a higher current than the stuff used back in the 80's, so although it looks thinner, it is still able to carry the same current. The wire I used to connect my old Pacet fan (and Karen's fan), was much thinner than the E30 stuff, but had the correct current rating.

Anyway, enough of my ramblings. PM me your address, and I'll pop this connector housing in the post

Cheers,

Ian.

[Brianmoooore]

Ordinary PVC insulated wire has a current rating of 30A in free air and 24A enclosed, so should be adequate for the job, current wise.
It's the voltage drop that will get excessive if you use wire that is too thin.