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Discussion Starter · #1 ·
When the resistor went on the '87 9000 ACC I couldnt get a replacement so wired up a permanent feed from the battery to a switch in the car so I could turn the blower motor either full blast or not at all! (I know, I know!) Problem is now I am about to possibly get a resistor the vents never go where I tell them too (i.e the bit of the ACC which controls where the airflow go's too, never wants to vent screen, always stays on one below windoscreen and above footwell!) and the heater blower seems to be extremely slow all of a sudden. How do I move the vent manually if I have too, and how do I change the motor that controls the vent director and what could be causing the blower to go slow.
 

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I don't know much about the early cars, but I suspect they are similar to mine. There are two stepper motors behind the dash that move the air distribution and temperature flaps. They are easy to spot once you take the top of the dash off. However, removing them was a fairly stressful operation. Good luck.
 

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Discussion Starter · #3 ·
So the stepper motor for the ventilation flap can be removed with just the top of the dash off.....no removing the whole dash?? If thats the case its a bit of a relief. Now I'm just worried about the blasted blower motor...and why its running slowly!!
 

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Is your switch rated to switch the motor? I would imagine it draws quite a lot of juice. Also, when you switch off, you will probably get a lot of arcing on the contacts because of the inductive load. So that may be one reason - the switch you fitted degrading.
 

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Discussion Starter · #9 ·
ACC old style with three speed fans. The resistor is still in place on top of the blower motor but its not doing anything as the point at which it connects to the blower motor is now connected to the battery direct. The blower motor is running very slow though.
 

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Sounds like high resistance in the circuit. Could be the motor - seized bearings, brushes etc. (if it's that sort of motor)or the earthing point. Try running a wire from the motor "out" straight back to the negative side of the battery. If motor speeds up, it's the earth; if it doesn't, it's the motor.
 

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I'm guessing at bit here, but I very much suspect that the fan takes a lot of current when running flat out. If it worked well when you first wired it up directly, but now runs more slowly, it could be down to heat degradation of the wire or connectors. For example, if you used crimp type connectors rather than soldered connectors, a high current will get them hot, and both the wire and the connector will oxidise, further increasing the resistance of the system, and limiting the current further. Also, if this is the case, the connectors will get very hot in use, posing a serious fire risk.

Perhaps you should have a good look at the wires, connector and switch to see if anything looks distressed. Also, you could put a voltmeter across the fan when it is running. If you don't get close to 12V, there's a big resistance somewhere in the system.
 

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Discussion Starter · #12 ·
You could be correct on the wire bit. I used crimped connectors and an inline fuse going to a switch. First the fuse degraded itself due to the heat. Then the Switch collapsed due to the heat, now I guess it could be the wires. Why would all this degrade......thought it was designed to ber able to carry a small voltage like a car battery easily...but everything seems to oxidize like you say. I've never known this happen with permanent feeds to stereos.
 

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Discussion Starter · #13 ·
Also is everyone sure changing the stepper motor on the vent flap is just a dash top off job??? Can anyone tell me where the sensors are in the earlier type of ACC as theres no sun sensosr on the dash like newer ACC versions.
 

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I did manage to remove the stepper motors with just the dash top off, from a car in the scrappers, but I removed both including the brackets etc. Also, I didn't have to be too careful as it was a scrapped car. Removing the individual motors, dis/reconnecting the linkages etc will be very fiddly. I don't know much specifically about the early systems though.

Heat loss in electrical circuits is equal to the resistance multiplied by the current squared. So a high current device, like a fan on full, will produce quite a lot of heat in the wiring/switch/connectors/fuse. Anything that causes localised additional resistance, like a crimped connector, will become a localised heat source. The connector and wire end get hot, the surfaces become oxidised which further increases the resistance, which further increases the heat produced and so on until something breaks or catches fire.

You need to use thick wire (30A rated), a heavy duty switch, and soldered connectors throughout, including the earth line.
 

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Discussion Starter · #15 ·
I used household 3 core wire. A switch from motorworld that you would have said would be up to the task! And crimped ends (now I understand a big no, no!) I'm in the process of getting a resitor so I am hoping to avoid having to renew this informal wiring. I have though somewhere in my garage got as stepper motor i got for an old 9000 of mine I ended up selling. This 9000 stepper motor I think was for the temperature control not the vents but are they both the same in design?
 

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Discussion Starter · #17 ·
Mark...did you manage to find out if the stepper motors were the same or not? I've got one in the garage I can reuse. I hope one for a 1990 will be the same on an older type ACC for an '87 model. Can anyome confirm this...also is it defiantely without question just a top off job???!!!
 
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