Solved: Final stage resistor

Silverzedtom · Post by **Silverzedtom** » Sat Dec 22, 2018 1:04 pm

I’ve had my suspicions for a while... blower fan pulsing when on max or a fast setting on both A/C on and off. Sounds like the final stage resistor is gone.

I want to get it sorted ASAP before it starts drawing current as I’m not using the car enough at the moment.

No bmw dealer in the uk has one and apparently it could take up to 3 months to get one.

Anyone know if should avoid certain brands if I went OE?

Has anyone had the pleasure? From what I’ve read it’s a common fault and a bit of a pig to swap (edit: on the e46)

Smartbear · Post by **Smartbear** » Sat Dec 22, 2018 1:45 pm

If the resistor had gone the fan wouldn’t be working?
Rob

MACK · Post by **MACK** » Sat Dec 22, 2018 1:56 pm

Never heard of the resistor failing on an E85 to be honest. Have you tried GSF (use VIP60 for 60off if you do) and Euro for one? At least its likely to be decent quality from one of them. It does sound like the classic symptoms of one failing from my E46 experience. I wonder if it could be the control/switch panel itself, but then again I've never heard of one of them failing either. How healthy's the battery, we all know how temperamental E85's are to a dicky battery

Silverzedtom · Post by **Silverzedtom** » Sat Dec 22, 2018 2:30 pm

Smartbear wrote: ↑Sat Dec 22, 2018 1:45 pm If the resistor had gone the fan wouldn’t be working?
Rob

I think when the resistors go the units unable to give constant resistance and it starts to wander, getting worse as time goes on. I’m a bit worried it will bugger the fan if I leave it for too long. There’s loads online about my exact symptoms for e46’s but not a lot about it on the e85.

As the e46 shares some components I’m hoping It’s this. I’m happy enough to give it a go at £50 all in. If it wasn’t such a pain to get to I’d get a multi meter on it

Silverzedtom · Post by **Silverzedtom** » Sat Dec 22, 2018 2:52 pm

MACK wrote: ↑Sat Dec 22, 2018 1:56 pm Never heard of the resistor failing on an E85 to be honest. Have you tried GSF (use VIP60 for 60off if you do) and Euro for one? At least its likely to be decent quality from one of them. It does sound like the classic symptoms of one failing from my E46 experience. I wonder if it could be the control/switch panel itself, but then again I've never heard of one of them failing either. How healthy's the battery, we all know how temperamental E85's are to a dicky battery

Good point RE the battery. It hasn’t had one in my ownership and has always done low mileage.

Thanks for the codes

, I have checked both but nothing comes up. Anywhere that lists them doesn’t have stock. I’m half tempted to order one from bmw and keep the fan speed low.

Smartbear · Post by **Smartbear** » Sat Dec 22, 2018 4:49 pm

Silverzedtom wrote: ↑Sat Dec 22, 2018 2:30 pm
Smartbear wrote: ↑Sat Dec 22, 2018 1:45 pm If the resistor had gone the fan wouldn’t be working?
Rob
I think when the resistors go the units unable to give constant resistance and it starts to wander, getting worse as time goes on. I’m a bit worried it will bugger the fan if I leave it for too long. There’s loads online about my exact symptoms for e46’s but not a lot about it on the e85.

As the e46 shares some components I’m hoping It’s this. I’m happy enough to give it a go at £50 all in. If it wasn’t such a pain to get to I’d get a multi meter on it

The final resistor failed on my Elise (they’re prone to this) and the fan wouldn’t run on the setting the resistor was applicable to. No pulsing, it just stopped completely

Rob

Smartbear · Post by **Smartbear** » Sat Dec 22, 2018 4:52 pm

Are you completely sure it’s the blower fan pulsing?
The reason i ask is because when the water pump started to fail on my 3.0si the main cooling fan started pulsing.
It’s was pretty loud & could have been mistaken for the blower fan.
How many miles has your si covered?
Rob

Silverzedtom · Post by **Silverzedtom** » Sat Dec 22, 2018 6:23 pm

Smartbear wrote: ↑Sat Dec 22, 2018 4:52 pm Are you completely sure it’s the blower fan pulsing?
The reason i ask is because when the water pump started to fail on my 3.0si the main cooling fan started pulsing.
It’s was pretty loud & could have been mistaken for the blower fan.
How many miles has your si covered?
Rob

Im on 47000 at the moment, when I got it it was on about 25000 just over two years ago. At points it was doing a few hundred miles between MOT’s. I’m only doing a hundred miles a month or less at the moment. I first heard the pulsing about two months ago but it’s slowly getting worse. It’s every time I whack it up now.

I’ll be taking it out tomorrow, I’ll keep an eye on the temp gauge although I’m sure it’s the blower. It seems to be worse for the first few minutes after a cold start... perhaps another indication it’s battery related. The pulsing also stops when the fan speed knobs turned off or below 3/4.

I’ve seen a lot of the pump issues on here, I’m hoping that’s got another year or two yet

Smartbear · Post by **Smartbear** » Sat Dec 22, 2018 7:24 pm

Silverzedtom wrote: ↑Sat Dec 22, 2018 6:23 pm
Smartbear wrote: ↑Sat Dec 22, 2018 4:52 pm Are you completely sure it’s the blower fan pulsing?
The reason i ask is because when the water pump started to fail on my 3.0si the main cooling fan started pulsing.
It’s was pretty loud & could have been mistaken for the blower fan.
How many miles has your si covered?
Rob
Im on 47000 at the moment, when I got it it was on about 25000 just over two years ago. At points it was doing a few hundred miles between MOT’s. I’m only doing a hundred miles a month or less at the moment. I first heard the pulsing about two months ago but it’s slowly getting worse. It’s every time I whack it up now.

I’ll be taking it out tomorrow, I’ll keep an eye on the temp gauge although I’m sure it’s the blower. It seems to be worse for the first few minutes after a cold start... perhaps another indication it’s battery related. The pulsing also stops when the fan speed knobs turned off or below 3/4.

I’ve seen a lot of the pump issues on here, I’m hoping that’s got another year or two yet

The temp gauge on my car never deviated from its normal position, the pump hadn’t failed but was operating below normal levels.
If you say the noisy fan changes when you alter the blower speeds it probably isn’t the cooling fan although mine was only pulsing after a cold start...

Rob

ph001 · Post by **ph001** » Sat Dec 22, 2018 10:45 pm

I bet it’s not the resistor... never heard of one failing on an E85. In fact I thought it was controlled electronically on the CANBUS

Mr Tidy · Post by **Mr Tidy** » Sat Dec 22, 2018 11:27 pm

It's surprising the resistor isn't an issue on the Z4s as it's a very common problem on the E46 - I can only assume it isn't be a shared part.

When the resistor went on my nephew's E46 it kept draining the battery. And it's certainly a PITA to change on an E46! The general consensus is to buy OEM, then you only buy once.

I never had the fan pulsing on my E86 when the water pump died - I had just put petrol in it and less than a mile later the temperature gauge was in the red with the warning light flashing.

That was at 60K miles and 10 years.

When the water pump died on my E91 325i (also an N52 engine) again I got no fan pulsing, just an amber temperature warning light that turned red in about half a mile (no temperature gauge, but why should there be when there is no dipstick either)

But that was after 12 years and 135K.

At least you can see what speed the blower fan is running at on the A/C controls.

Silverzedtom · Post by **Silverzedtom** » Sun Dec 23, 2018 10:18 am

ph001 wrote: ↑Sat Dec 22, 2018 10:45 pm I bet it’s not the resistor... never heard of one failing on an E85. In fact I thought it was controlled electronically on the CANBUS

where would you start the search? I’ll be doing a cold crank test soon - my multimeters at work at the moment

. If the batteries ok I was going to start with a new FSR, unless you’d suggest I look elsewhere first?

Silverzedtom · Post by **Silverzedtom** » Sun Dec 23, 2018 10:27 am

Mr Tidy wrote: ↑Sat Dec 22, 2018 11:27 pm It's surprising the resistor isn't an issue on the Z4s as it's a very common problem on the E46 - I can only assume it isn't be a shared part.

When the resistor went on my nephew's E46 it kept draining the battery. And it's certainly a PITA to change on an E46! The general consensus is to buy OEM, then you only buy once.

I never had the fan pulsing on my E86 when the water pump died - I had just put petrol in it and less than a mile later the temperature gauge was in the red with the warning light flashing. That was at 60K miles and 10 years.

When the water pump died on my E91 325i (also an N52 engine) again I got no fan pulsing, just an amber temperature warning light that turned red in about half a mile (no temperature gauge, but why should there be when there is no dipstick either) But that was after 12 years and 135K.

At least you can see what speed the blower fan is running at on the A/C controls.

I was expecting the unit to carry the same part number but it doesn’t and as there seem to be virtually no reports on the e85’s unit I don’t think it is the same part at all. A bit strange but it would be just my luck that Mines gone

I always prefer oem, as you say fit the part and forget. If My batteries good I’ll order one from bmw and sit tight.

Not looking forward to the pump going, I’ll have to get a preventative maintainance list up together, I’d rather replace it early than get caught out in the middle of nowhere

firebobby · Post by **firebobby** » Sun Dec 23, 2018 2:33 pm

I fitted a new resistor to my sons Transit van as it would only work on position 4 and not 1 2 or 3. Now works fine

Silverzedtom · Post by **Silverzedtom** » Sat Dec 29, 2018 10:15 pm

Pleased to report a new battery has done the trick. No date stamp on the old one but it wasn’t oem. In went a Varta E44 and the fans now solid as a rock

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