My inside blower fan has died - I cannot now demist front screen or have any air blown through the vents.

Over last few days it made an occasional rattle like something was loose inside then stopped altogether.

 

After pulling passenger side dash apart and locating the blower I noticed the plug that goes into it has fused onto the plastic shroud of the motor and the wires were slightly blackened and stuck together at the plug. Not good.

after cutting back the wire back to the good bits and re-extending the wire (solder with 17a cable) - I fitted 2 spade connectors and when I switch fan or a/c on i get about 8-9 volts whilst blower is unconnected? (I thought it should be 12v as per battery).

Anyway - the minute I connect the blower to it I lose all voltage on that line - I tap into it and it reads 0v?????

 

I have put a meter across the contacts of the blower and am getting a near short (a few ohms) - what should this be??

 

However. . . . . . . . . If I connect the blower straight to the battery it works fine? I have tried swapping the relays about in case it was that but am still stuck.

 

please please please help!!!!!!!!!!!!!!!!!!!!!!!!

Jason,

 

Understanding any car electrical system requires a little more than normal common sense! and the reason? auto electric's almost defy explanation sometimes.

 

However I will try to work through your particular problem with the small info we have.

 

Firstly sounds like your blower motor is just fine, the low resistance reading you have is normal, when taking readings across D.C. motor windings with a test meter the internal resistance will be very low as test meters themselves operate on very low current ( millivolts ) and most modern meters which are lcd display have a very low internal resistance also, which in some cases can give misleading readings, correctly understanding the tests you are doing and the figures you get is the key to fault finding.

 

The low voltage you are reading that disappears when the motor is connected can be caused by a back feed or when very high resistance is evident in the supply feed or earth return control cable, this + v supply can be read by the very low input meter but as soon as a load is applied the high resistance of the feed will prevent current flow and hence the voltage you previously seen will appear to disappear, however in your case as the motor is earth switch controlled that makes for even more confusion.

 

As with many of the electrical units in the 300zx Nissan decided to operate things like the headlights, blower, fuel pump, etc. by controlling the earth return line.

 

This means there is + 12 volts to the units controlled by the ignition switch, then the earth wire is the controlling system, this means though when checking for faults you will find a supply voltage but the item does not work, this is because the earth control cable is the fault or where ever the earth control cable is switched, unless you are familiar with this type of wiring system it can get very confusing as it appears that you have power but the unit is not operating.

 

In the case of the blower motor, the fan speed is varied by a resistor pack, if this fails it can cause excess current draw and cause cables to burn out as they are working above the correct capacity and getting too hot, eventually the pack it self will fail and go open circuit.

 

 

I would take a look at the resister pack and the associated wiring to this, as a work around you could use the original + v supply feed and just add a temporary switch to your own earth control cable direct to the motor however the fan will run at full speed all of the time.

 

The reason for the work around? the resister pack replacement requires the dashboard to be removed!!! :eek:

 

Hope that helps with a few basics

 

Jeff TT

bugger!!!! its never anything small or easy on my car

Cheers Jeff - appreciated!!!

is there any way of proving the resistor pack is shot? could it be anything other than the resistor pack? Can you say whereabouts the resistor pack is located - is there any way of swapping without removal of complete removal of dashboard? I will try and do the temp work around for now and just run a constant earth to the blower so when it comes on it'll be on full time. - thanks again.

Jason,

 

Understanding any car electrical system requires a little more than normal common sense! and the reason? auto electric's almost defy explanation sometimes.

 

However I will try to work through your particular problem with the small info we have.

 

Firstly sounds like your blower motor is just fine, the low resistance reading you have is normal, when taking readings across D.C. motor windings with a test meter the internal resistance will be very low as test meters themselves operate on very low current ( millivolts ) and most modern meters which are lcd display have a very low internal resistance also, which in some cases can give misleading readings, correctly understanding the tests you are doing and the figures you get is the key to fault finding.

 

The low voltage you are reading that disappears when the motor is connected can be caused by a back feed or when very high resistance is evident in the supply feed or earth return control cable, this + v supply can be read by the very low input meter but as soon as a load is applied the high resistance of the feed will prevent current flow and hence the voltage you previously seen will appear to disappear, however in your case as the motor is earth switch controlled that makes for even more confusion.

 

As with many of the electrical units in the 300zx Nissan decided to operate things like the headlights, blower, fuel pump, etc. by controlling the earth return line.

 

This means there is + 12 volts to the units controlled by the ignition switch, then the earth wire is the controlling system, this means though when checking for faults you will find a supply voltage but the item does not work, this is because the earth control cable is the fault or where ever the earth control cable is switched, unless you are familiar with this type of wiring system it can get very confusing as it appears that you have power but the unit is not operating.

 

In the case of the blower motor, the fan speed is varied by a resistor pack, if this fails it can cause excess current draw and cause cables to burn out as they are working above the correct capacity and getting too hot, eventually the pack it self will fail and go open circuit.

 

 

I would take a look at the resister pack and the associated wiring to this, as a work around you could use the original + v supply feed and just add a temporary switch to your own earth control cable direct to the motor however the fan will run at full speed all of the time.

 

The reason for the work around? the resister pack replacement requires the dashboard to be removed!!! :eek:

 

Hope that helps with a few basics

 

Jeff TT

correct me iff ime wrong jeff but i thought the resister pack is that unit that screws onto the motor cowling with the ally fins on it,iff i am wrong then ive been hanging on to this unit for nothing then :rofl: knowing the complex design of these cars it proberly regulates the paint fade on the wiper cowling :D :D

thats just what Im about to check now. . . .

here's hoping.

right - looks like neg wire is controlled by this thing as Jeff stated.

 

Im hoping this is the resistor box that he's on about.

 

Ive took it apart as you can see and something is rattling around inside - not good - sounds like a screw

Im just seeing if I can strip it down any further

right - popped off black plastic cover as shown and a couple of large pieces of solder fell out

 

in the last pic I removed the screw that holds a copper arm in place that looks like it was soldered with a large blob to the bottom arm - pic is a bit fuzzy.

 

why solder - why not wire?

 

any ideas?

 

Cheers

sorted it - bridges the 2 gold terminals back up with a large blob of solder (bottom plate not as conductive - had hell of a time getting solder to stick) - chucked it all back in and it works

 

Cheers for the advice people.

Hi

have you got any better pics as i'm having the same problem as you and would like to sort it. Did you find out how much a replacement part costed?

Hi

have you got any better pics as i'm having the same problem as you and would like to sort it. Did you find out how much a replacement part costed?

 

Five years later I reckon he wont have any pics:tt2:

why does it show Jeff TT as a guest???

Because if you look at his username on that post, the "TT" is spaced from the word Jeff.

Now it is joined togther so it's all one.

So would imagine that was a 2nd username he used back then and is no longer valid :-)

smithy

Five years later I reckon he wont have any pics:tt2:

 

Yes i agree, but i thought someone else might've read it and had something constructive to offer.......you did,........ but you didn't

 

Naaaa, i just didn't read the date or anything just saw, read it, replied....

Thanks for making me feel like a donkey though( there's always one ) I would totally make my day if he has got some more pictures....in HD ( an i'd be like " In your Face Slick Pete, What ya got to say now ? ..... an stuff! )

Anyway.....

I pulled the amp out and took it apart to find it was perfect inside, no broken contacts or signs of burned out terminals etc so that's sorted, i'm gonna run that through with a tester and cancel that out of the equation, Then I'm onto the relay, which i'm looking for a replacement ( anything to advise there " MISTER " Slick? )

Yes i agree, but i thought someone else might've read it and had something constructive to offer.......you did,........ but you didn't

 

Naaaa, i just didn't read the date or anything just saw, read it, replied....

Thanks for making me feel like a donkey though( there's always one ) I would totally make my day if he has got some more pictures....in HD ( an i'd be like " In your Face Slick Pete, What ya got to say now ? ..... an stuff! )

Anyway.....

I pulled the amp out and took it apart to find it was perfect inside, no broken contacts or signs of burned out terminals etc so that's sorted, i'm gonna run that through with a tester and cancel that out of the equation, Then I'm onto the relay, which i'm looking for a replacement ( anything to advise there " MISTER " Slick? )

 

:ohmy::oops:

smithy

Because if you look at his username on that post, the "TT" is spaced from the word Jeff.

Now it is joined togther so it's all one.

So would imagine that was a 2nd username he used back then and is no longer valid :-)

smithy

 

CORRECT :clap:

 

JeffTT

Hi

have you got any better pics as i'm having the same problem as you and would like to sort it. Did you find out how much a replacement part costed?

 

We have the fan speed resister in stock £20 inc delivery, can post up some pics for your with clearer location if you wish.

 

Jeff TT

He! He!

JeffTT

 

E-mail me with payment details through paypal if you want, for that price i'ts worth me having it as a spare

 

christopher.ottey@gmail.com

CORRECT :clap:

 

JeffTT

 

why did you change your name then Jeff?