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Using a 6 volt wiper motor on a 12 volt system

 
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Using a 6 volt wiper motor on a 12 volt system
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Den Hewitt



Joined: 09 Nov 2008
Posts: 396
Location: North Somerset, England

Post Using a 6 volt wiper motor on a 12 volt system Reply with quote
I found this on a VW website:

Running 12 volts through the 6-volt wiper motor will cause the motor to run too fast, resulting in the linkages prematurely wearing out, making the wipers hard to turn the wipers off in the correct position on models without self-parking, and eventually causing the wiper motor to burn out.
By fitting a limiting device of the correct values it will overcome the previously mentioned problems. With no commercially made limiter on the market made for this purpose, you will have to make one. This is a very simple operation, taking approximately one hour, and costing about $10.00.
Note: this limiter is design to work only on the wiper. It doesn't reduce 12 volts to 6 volts, it is a current limiter, designed to work with the load imposed by the wiper motor. It will also be MUCH more reliable than placing a simple load resistance in the wiper circuit.
Obtain the following from an Electronic Supplier -
1- 330 OHM watt resistor
1- 470 OHM 1 watt resistor
1- TIP 142 transistor (NPN 10amp 100 volt rating)
1- TO3 insulation pack ( mica and nylon washer)
1- tube heat sinking compound
You will also need the following -
100mm of aluminium angle ( 25mm x 25mm x 3mm )
some automotive wire
A diagram of the circuit is below.
Now to assemble -- take the TIP142 transistor (see NOTE at bottom for transistor substitution), hold with part number up and the three legs pointing towards you. Bridge (connect) the left hand leg to the middle leg using the 330 OHM watt resistor, soldering into position. Solder the 470 OHM 1 watt resistor to the end of the left leg and then a length of wire (brown) to the other end of that resistor. Solder a length of wire (red) to the middle leg. Finally then, solder a length of blue wire (approx. 6" to 12" long, depending on where you mount the resistor) to the right hand leg).
_________
| |
| TIP142 |
---------
|B |C |E
|-330-| |
| | B
470 R L
| E U
B D E
R | |
O | switch
W Fuse
N
|
Earth



The B, C, E annotations above are Base, Collector, Emitter, and are noted in case you can not find a TIP142 and need to use a substitute - see NOTE below.
Because the transistor generates some heat, it is necessary to fit it to a heat sink to ensure maximum life. Lance has had some on vehicles for over eight years now with out any problems when fitted as follows. Some aluminium angle 4 inches (100mm) long will do, drill a hole in the angle, larger than the bolts to be used, and fix the transistor to the angle, placing the insulation (mica) between the transistor and angle, and using a small amount of heat sink compound (to aid the heat transfer) on both sides of the mica. Place the nylon washer between the nut of the retaining bolt and the transistor. Meaning, that the transistor and the mounting bolt should not make direct physical contact with the aluminium angle, but still be mounted firmly to it. This prevents electrically shorting the transitor and bolt, whilst allowing good heat flow to the heat sink. Now drill two holes in the aluminum angle (other side ) so you can mount it to the body of the car; again use the heat sink compound ( between the aluminium angle and the body) to aid heat transfer. The car's body now becomes part of the heat sink and ensures that the transistor just gets warm - not hot. This is a much safer situation than using a simple load resistor, which would be liable to get really hot.
Now connect to the vehicle. Remove the power wire from the fuse box to the wiper switch. Hold the transistor as before (part number up, wires pointing towards you). Connect the wire on the left to an earth (body of the vehicle). The wire in the middle is connected to the fuse box, and the wire on the right is connected to the wiper switch.
You should now have wipers which work at the correct speed, and no dangerous hot-spots which might be caused by a simple load resistor
-----------

Now back to me, as I have posted before one of my 3 Tractions is converted to 12 volts and all I have done is to fit a 12volt wiper motor ( I was able to do this as it is a cabriolet). The fuel gauge, fuel sender and ammeter are all 6 volt and work perfect;y well with no problems.
The clock never worked and I have not yet tried to find another clock to try and use. All bulbs are of course 12
volt.
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11BL Legere (rhd), 11B Normale, 11B Cabriolet



Mon Jan 18, 2010 10:32 am Den Hewitt is offline View user's profile Send private message Visit poster's website
Den Hewitt



Joined: 09 Nov 2008
Posts: 396
Location: North Somerset, England

Post Reply with quote
Sorry but the wiring diagram did not post very well, I will use a drawing program and post it as a photo later today.

Den
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11BL Legere (rhd), 11B Normale, 11B Cabriolet
Mon Jan 18, 2010 10:38 am Den Hewitt is offline View user's profile Send private message Visit poster's website
Den Hewitt



Joined: 09 Nov 2008
Posts: 396
Location: North Somerset, England

Post Wiring diagram Reply with quote
Now posted as photo
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Traction Wedding Cars http://www.tractionweddingcars.co.uk/
11BL Legere (rhd), 11B Normale, 11B Cabriolet
Mon Jan 18, 2010 11:35 am Den Hewitt is offline View user's profile Send private message Visit poster's website
Den Hewitt



Joined: 09 Nov 2008
Posts: 396
Location: North Somerset, England

Post Reply with quote
Wiljan Cats posted on the TA-L Yahoo group "I use in post 1952 cars the wiper motor
(and frame) from a 2CV."
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11BL Legere (rhd), 11B Normale, 11B Cabriolet
Mon Jan 18, 2010 11:37 am Den Hewitt is offline View user's profile Send private message Visit poster's website
kbtw



Joined: 04 Dec 2008
Posts: 108
Location: The Netherlands

Post Reply with quote
Den, you are absolutely right: a simple resistor in the 12v power cable to the 6v wiper motor will not work to satisfaction. There are various reaons, one and not the least being the risk of fire. The post '52 6v wiper motor has a load of some 16 watt. Since the current will not be less, one will need to dissipate the equivalent of 16 watt in terms of heat. From experience, I know that a resistor capable of handling such a power can get awfully hot and can cause burns or materials like plastic to melt and catch fire. I have tried one on a heat sink and even this gets too hot after a wile.

The other, more technical reason is that a fixed resistor will not take the physical load of the motor into account. In other words, if the resisistor (something between 2.8 and 3,3 Ohms is the correct value) is OK for a motor + wipers on a wet windscreen, the motor will coem to a halt (or not start up in the first place) with the wipers on a dry or partially dry screen.

On my 12v Traction I have solved the 12v conversion problem in an effective manner by using a commercially available 2000 mA stabilised DC-DC converter that is normally used to charge digital camera batteries from a car cigarette lighter plug. This converter has a stabilised 7.0v setting and I have found that this is ideal to make the wiper motor run at a stable, constant speed, moving the wipers across the screen as if they were the ones of my 6v Traction (i.e. not too slow and not too fast).
Thu Feb 04, 2010 4:35 pm kbtw is offline View user's profile Send private message Visit poster's website
Den Hewitt



Joined: 09 Nov 2008
Posts: 396
Location: North Somerset, England

Post Reply with quote
As you know I have a French traction that is converted to 12 volts and that I run everything except the wiper motor and clock on 12volts. I have a 12volt wiper motor but never bothered with the clock - until now. I have just bought a 12v to 6v reducer that is available for VW beetle and camper vans. The packet says that it is for use with wiper motors . I have used it for the clock and no problems. It cost me 10.
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11BL Legere (rhd), 11B Normale, 11B Cabriolet
Mon Sep 06, 2010 3:13 pm Den Hewitt is offline View user's profile Send private message Visit poster's website
kbtw



Joined: 04 Dec 2008
Posts: 108
Location: The Netherlands

Post Reply with quote
Dan, this monster is a resistor capable of some 20 watts or so! It is indeed capable of handling the power of a wiper motor but will get quite hot when you try to do this. For the electric clock it is like a giant compared to the millamperes that run through the small coil. You could easily do with a miniature resistor of 0,25 or 1 watt capacity for this. At least with this beast there is no risk of the resistor running hot! The original 6v clock of my 12v Traction runs perfectly well on 12v and has done so for years now. Although not strictly necessary, I have inserted a small resistor (forgot how many ohms) in the power line to the fuel gauge.
Mon Sep 06, 2010 9:54 pm kbtw is offline View user's profile Send private message Visit poster's website
Den Hewitt



Joined: 09 Nov 2008
Posts: 396
Location: North Somerset, England

Post Reply with quote
I have already burnt out a clock trying it directly on 12volts. I'll let you know if this thing runs hot.
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Traction Wedding Cars http://www.tractionweddingcars.co.uk/
11BL Legere (rhd), 11B Normale, 11B Cabriolet


Last edited by Den Hewitt on Tue Sep 07, 2010 8:16 am; edited 1 time in total
Tue Sep 07, 2010 8:09 am Den Hewitt is offline View user's profile Send private message Visit poster's website
Den Hewitt



Joined: 09 Nov 2008
Posts: 396
Location: North Somerset, England

Post Reply with quote
I have just been in the garage to check it as it has been on the car for 12 hours. It is not what you think it is as it is cold, no sign of any heat at all. Oh and the clock is accurate, no time gain or loss.
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Traction Wedding Cars http://www.tractionweddingcars.co.uk/
11BL Legere (rhd), 11B Normale, 11B Cabriolet
Tue Sep 07, 2010 8:15 am Den Hewitt is offline View user's profile Send private message Visit poster's website
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