Some folks have complained that their electric wipers, using the 90-96
Lumina APV motor with my kit, sweep too fast. Several years ago some of
the Canadians began to use the resistor used with Daylight Running Lights
up there as a ballast resistor to slow the motor.
The number of folks asking about slowing the motor has finally reached the
number necessary to generate a tuit for me. So, over the past couple of
weeks I've been investigating the question. I've now got a couple of ways
to simply reduce the sweep speed:
The only reasonable way I've found to reduce the speed is by reducing the
voltage supplied to the system. There are a couple of simple, inexpensive
ways to do that:
1. A simple 1 Ohm resistor inserted between the circuit breaker and
the lead to the wipers will reduce the motor's speed to what appears to me
to be a more reasonable speed. Without actually measuring the reduction,
I'd guess it to be about 25%-30%. I've gotten some metal cased resistors,
rated for 100 Watts dissipation and tried one on the work bench. Despite
its rating, it does get hot after extended use, even though it's only
dissipating about 2.5 Watts. I have not mounted it; screwing it to the
firewall would help significantly.
2. An even simple method, and potentially more versatile, is to use a
bridge rectifier as the "dropping resistor". Connecting the (-) terminal
of the bridge to the output of the CB, and the (+) terminal (diagonally
opposite the (-)) to the wipers yields about the same speed reduction as
the 1 Ohm resistor. If the wipers are connected to one of the ac terminals
(the two not marked (+) or (-)) the speed reduction is only about 15%.
Again, the bridge does get hot eventually so it should be screwed to the
firewall as a heat sink.
Either of those methods can be very easily implemented, and with only
slightly more difficulty, a selector switch could be added. A simple SPST
switch could be connected directly across the resistor to eliminate it
whenever desired. The bridge offers that simple solution or, a SPDT could
be used to select any two of the three speeds it offers (Lo, Med, Hi).
With a SPDT-CO switch, selection of any one of the 3 is feasible. I'll
provide details if anyone happens to need them.
There is a significant problem with either of these modifications: For
those few people who've wired their wipers to the ACC circuit instead of
the BATT, if the ignition is turned on with the wipers already in the Lo or
Med position, with the original switch in the HI position, the wiper motor
WILL NOT start in most cases. Instead it will draw a very high stall
current, potentially burning something out. The simple solution is to
always turn the wipers OFF before killing the engine. For those whose
wipers are connected so they MUST be returned to OFF (Parked), the problem
can't arise.
The parts are trivially inexpensive: $0.99 for either a 25A 400VDC (which
I recommend), or a 1 Ohm 100 Watt resistor, shipping from China included,
on eBay. Just search for "25 A Bridge" with "Lowest price with shipping"
sort option. If there's enough demand, I'll put together a kit, but it
hardly makes sense because I'll have to charge $5.00 or more to cover
handling, postage, etc.
What I have NOT done, since we haven't had much rain this summer, is
actually test the modifications with the wipers working on the windshield.
I hope someone in a rainy region will test it and let us all know if it's
satisfactory.
Give me a call or a note if you need more info.
Oh yeah, I've got the bridge setup running on the work bench tonight to see
just how hot the bridge is in the morning. That's easier than mounting it
on my GMC, where the wiring is routed so as to make the installation
difficult.
Ken H.
Lumina APV motor with my kit, sweep too fast. Several years ago some of
the Canadians began to use the resistor used with Daylight Running Lights
up there as a ballast resistor to slow the motor.
The number of folks asking about slowing the motor has finally reached the
number necessary to generate a tuit for me. So, over the past couple of
weeks I've been investigating the question. I've now got a couple of ways
to simply reduce the sweep speed:
The only reasonable way I've found to reduce the speed is by reducing the
voltage supplied to the system. There are a couple of simple, inexpensive
ways to do that:
1. A simple 1 Ohm resistor inserted between the circuit breaker and
the lead to the wipers will reduce the motor's speed to what appears to me
to be a more reasonable speed. Without actually measuring the reduction,
I'd guess it to be about 25%-30%. I've gotten some metal cased resistors,
rated for 100 Watts dissipation and tried one on the work bench. Despite
its rating, it does get hot after extended use, even though it's only
dissipating about 2.5 Watts. I have not mounted it; screwing it to the
firewall would help significantly.
2. An even simple method, and potentially more versatile, is to use a
bridge rectifier as the "dropping resistor". Connecting the (-) terminal
of the bridge to the output of the CB, and the (+) terminal (diagonally
opposite the (-)) to the wipers yields about the same speed reduction as
the 1 Ohm resistor. If the wipers are connected to one of the ac terminals
(the two not marked (+) or (-)) the speed reduction is only about 15%.
Again, the bridge does get hot eventually so it should be screwed to the
firewall as a heat sink.
Either of those methods can be very easily implemented, and with only
slightly more difficulty, a selector switch could be added. A simple SPST
switch could be connected directly across the resistor to eliminate it
whenever desired. The bridge offers that simple solution or, a SPDT could
be used to select any two of the three speeds it offers (Lo, Med, Hi).
With a SPDT-CO switch, selection of any one of the 3 is feasible. I'll
provide details if anyone happens to need them.
There is a significant problem with either of these modifications: For
those few people who've wired their wipers to the ACC circuit instead of
the BATT, if the ignition is turned on with the wipers already in the Lo or
Med position, with the original switch in the HI position, the wiper motor
WILL NOT start in most cases. Instead it will draw a very high stall
current, potentially burning something out. The simple solution is to
always turn the wipers OFF before killing the engine. For those whose
wipers are connected so they MUST be returned to OFF (Parked), the problem
can't arise.
The parts are trivially inexpensive: $0.99 for either a 25A 400VDC (which
I recommend), or a 1 Ohm 100 Watt resistor, shipping from China included,
on eBay. Just search for "25 A Bridge" with "Lowest price with shipping"
sort option. If there's enough demand, I'll put together a kit, but it
hardly makes sense because I'll have to charge $5.00 or more to cover
handling, postage, etc.
What I have NOT done, since we haven't had much rain this summer, is
actually test the modifications with the wipers working on the windshield.
I hope someone in a rainy region will test it and let us all know if it's
satisfactory.
Give me a call or a note if you need more info.
Oh yeah, I've got the bridge setup running on the work bench tonight to see
just how hot the bridge is in the morning. That's easier than mounting it
on my GMC, where the wiring is routed so as to make the installation
difficult.
Ken H.
