Fixed- Blower Motor Fuse keeps blowing

R

Rui Almeida

Dedicated Member
Joined
Aug 16, 2016
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44
Hi there guys,

Yesterday everything was fine but found myself with a frozen z3 and no blower motor working. Checked the fuse and was actually blown so just replaced it with a new one (also 10amps) and tried it with no results and the new fuse was now blown too. Btw mine doesn't work in the 4th position so I assumed isn't related with the resistor.

I read a thread about heater resistor and the actual fan but no one never mentioned anything about the fuse problem. Can anyone advise me towards this problem as it's pretty impossible to drive the car with this weather.

Thanks everybody, It's been a bad few days but hope the z3 gets back as it should.
 
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I'd be looking for a wiring short if the fuse blows right away or as @colb mentioned the motor may be worn and shorting out! Good luck finding it! JIM
 
colb said:
Useful info here
http://www.zroadster.net/forum/viewtopic.php?f=5&t=32647&p=306410&hilit=heater+blower#p306410

I would suspect the resistor being the cause if you don't have power on position 4, they usually fail on 1,2 and3 leaving just 4 working. If it isn't the resistor then could be either the speed switch itself or the motor shorting out.
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Yes I know that when they fail is usually on 1 2 3 and them 4 is working. I also realises that most of the problems whit the resistor are usually related with por connections points and soldering points and I am quite good with the soldering iron so will see.
Just think it's a bit odd the switch it self stop working but I am putting everything on the list. Will post some feedback today.

Thanks
 
oldcarman said:
I'd be looking for a wiring short if the fuse blows right away or as @colb mentioned the motor may be worn and shorting out! Good luck finding it! JIM
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Funny enough the fuse only blows when I turn the switch. Will have a look now that is apparently not raining and test everything I can.

Thanks
 
Hi guys ,

So after a couple tests and even after getting stuck not being able to remove the wiper blades I decided a different approach to see if both the resistor and the unit were working fine and I just put a 20amp fuse instead of the recommended 10amp one. So now everyone will say yes there's something wrong and yes is true but I managed to check that both units are working just fine as I've got 1 2 3 4 working and blower running quite and smooth.

What are you thoughts? Is that alright to just use the 20amp instead as that basically solves my whole problem of not being able to defrost and drive the car on the morning ?

Thanks in advance
 
If the original fuse required was 10 amp and a twenty gets everything going I'd think you stand a chance of overheating your wiring harness and wouldn't personally feel comfortable doing it! But I'' sure there are many more qualified than I am to answer to this question. Good luck JIM
 
oldcarman said:
If the original fuse required was 10 amp and a twenty gets everything going I'd think you stand a chance of overheating your wiring harness and wouldn't personally feel comfortable doing it! But I'' sure there are many more qualified than I am to answer to this question. Good luck JIM
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I think the same way, must be a reason why is 10 and not 20. It was nice to see that everything is working but would rather to fix it instead of taking the risk. Thanks any way mate
 
A 10A fuse should be well more than the expected running current needed and above the start up current needed to get the motor moving.

Have you tried a 10A fuse in since you got it going with a 20A fuse. Could be the motor was stalled an unable to get going before the fuse blew. As you've moved the motor again, there is a chance it might be fine (until it stops in a similar situation). Doesn't mean to say there isn't something wrong with the motor though. I'd rather not run a 20A fuse - as Jim said, you could be drawing too much current constantly and heating up something way beyond what it's expected to be.
 
Redline said:
A 10A fuse should be well more than the expected running current needed and above the start up current needed to get the motor moving.

Have you tried a 10A fuse in since you got it going with a 20A fuse. Could be the motor was stalled an unable to get going before the fuse blew. As you've moved the motor again, there is a chance it might be fine (until it stops in a similar situation). Doesn't mean to say there isn't something wrong with the motor though. I'd rather not run a 20A fuse - as Jim said, you could be drawing too much current constantly and heating up something way beyond what it's expected to be.
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It does make sense what you're saying of course. I will try another 10amp one after another quick test with the 20am fuse. A friend of mine that worked for BMW said from the top of his head "that must be a resistor failure of motor seized" unfortunately he couldn't have a look at the car so I am stuck with the theory. I was keen to inspect both the motor and the resistor but got stuck with the wiper blades not coming out. Will probably try again tomorrow.
Should I just another resistor and then another motor? Will a seized motor do this even though works fine with more current ?

Thanks in advance
 
I believe that if there is a burnt spot in the windings of the motor and the motor stops on that spot it will not usually get going with the normal current and allowing the extra current through may jump the dead spot. This happens quite often with starter motors and usually a crack with a hammer will move the windings past the point and will work fine until as @Redline states the spinning motor stops in the dead position again. hope this makes sense to you!! JIM
 
I am with the others on this, risky using the 20amp fuse for a long period when it should have a 10amp fitted, fair chance its the motor at fault as others have suggested, best replace with a known good unit and see if that fixes it with a 10amp fuse fitted
 
I might start with resistor being cheaper and see if it makes any difference if it doesn't might just get a good used one. Everyone be calm because I won't be using it with a 20amp fuse ahah.
 
Well one thing to remember. The heated mirrors are on the same fuse at the heater unit. Damp and frosty mornings with damp behind the mirrors may also lead to the fuse blowing. I actually got the wiper arms off with a small cheap bearing puller from Machine Mart. The small one is about £10 as works a treat when you have stuck arms. Spray some penetrating fluid such as WD40 and slowly apply the pressure after letting the oil do it trick. Sometimes they go with a bang when letting go. The heater resistor is easy to access under all the panels front of the windscreen. I have done a few now !! @Mr C will vouch for that one. The motor can come out easy enough too. Just remember that the plastic straps holding the cover on are probably brittle with age, so take your time and if possible not on a freezing morning.
 
pgunter said:
Well one thing to remember. The heated mirrors are on the same fuse at the heater unit. Damp and frosty mornings with damp behind the mirrors may also lead to the fuse blowing. I actually got the wiper arms off with a small cheap bearing puller from Machine Mart. The small one is about £10 as works a treat when you have stuck arms. Spray some penetrating fluid such as WD40 and slowly apply the pressure after letting the oil do it trick. Sometimes they go with a bang when letting go. The heater resistor is easy to access under all the panels front of the windscreen. I have done a few now !! @Mr C will vouch for that one. The motor can come out easy enough too. Just remember that the plastic straps holding the cover on are probably brittle with age, so take your time and if possible not on a freezing morning.
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You are an absolute genius mate!
I just remember that when I got the wing mirror broken I decided to remove the base and take the wiring from the base but because I was super lazy I decided to put the wiring back through the door and seal de whole. So all make sense now as Ive got the wiring for that wing mirror just hanging on the inside of the door and completely forgot the connectors for the heated mirror are actually exposed. I will give it a try and see if this is the cause!

Thanks so much for the tip! Fingers crossed then.
 
Thats what makes this forum so good... You actually get help from those that have done the work already...
 
@pgunter I can only sai you're a freaking genius! Ahaha Just ran outside under light rain removed the base of the wing mirror pulled the cables out and of course they were all exposed including heated mirror and mirror motors cables. Put a new 10amp fuse jumped in the car turned the switch on and everything works as usual! :)
 
Glad it's sorted, well done @pgunter

Sounds like you need a new wing mirror now rather than the heater blower, much easier to change too!
 
spurs fan in a coupe said:
Glad it's sorted, well done @pgunter

Sounds like you need a new wing mirror now rather than the heater blower, much easier to change too!
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I was about to send you a pm but now you know that I don't really need any of those two. Yes now is back to the original parts wing mirror and fog lamp. Prices a bit steep on wing mirror but easier to change any way.

Thanks for everything
 
Well as I said, I had a similar issue and it helps us all when we share the knowledge. Glad you have it sorted. Now put that 20amp fuse away before you set the dash alight.
 
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