Attention Electrical Gurus, Need help with windshield washer wiring Options

[bbrock]

Right after ordering a complete Car Magic kit to convert my windshield washer to electric, I read Sir Andy's excellent tech article on the conversion. The idea of pulling power for the washer pump off the intermittent wiper feed so the washer is activated by pulling back on the wiper lever was too elegant not to try.

I happened to have this nifty vintage VW style splitter I bought some time ago for not other reason than I thought it might come in handy for some future custom wiring project. It was just the ticket for splitting off of my intermittent washer relay to power the washer pump.



After hooking everything up, I pulled back on the wiper lever and HUZZAH! The washers squirted and the wipers ran for two sweeps and parked. Pretty slick! I couldn't understand how the intermittent wipers would work when the lever was pulled down to turn the intermittent wipers on. I pull down on the lever to test them and nothing. As soon as I unplug the washer pump, the intermittent wipers start running. I'm not sure how the intermittent relay works, but thinking the timer is from charging a capacitor which then "bump starts" the wipers to run a single cycle.

Is there is a reasonably simple way to isolate the pump so it allows the intermittent mechanism to run without activating the washer pump? Could be a fun project. Or should I just go back to the original plan of installing the Car Magic switch? I just like the idea of minimizing the wiring.

[Superhawk996]

Now that I've had some time to think about the LVD solution here are some thoughts.

I think the same overall goal of disconnecting the pump ground path from the intermittent relay could be achieved with a simple MOSFET transistor. The control input to the MOSFET gate would be the 12v input from Black/Brown stalk switch,

I can't tell from the specs for the proposed LDV if it can handle inductive loads or is just for resistive load like a light, LED, or battery.

Inductive loads (relays, motors) can generate voltage spikes that will damage electronic components when they are shut off abruptly. If a MOSFET were being used to switch the washer pump, I'd say that you would want to put a flyback diode in the circuit to protect the circuit.

Can't tell if the LVD proposed has internal flyback diodes. Maybe, maybe not depending on whether they designed it to handle inductive loads. You could easily add your own externally.

For $8 - can't go wrong even it it eventually dies from an inductive load. At that point you could switch to a MOSFET switch like this for around the same cost and is even smaller:

https://www.amazon.com/ANMBEST-High-Power-A...-spons&th=1

[bbrock]

Now that I've had some time to think about the LVD solution here are some thoughts.

I think the same overall goal of disconnecting the pump ground path from the intermittent relay could be achieved with a simple MOSFET transistor. The control input to the MOSFET gate would be the 12v input from Black/Brown stalk switch,

I can't tell from the specs for the proposed LDV if it can handle inductive loads or is just for resistive load like a light, LED, or battery.

Inductive loads (relays, motors) can generate voltage spikes that will damage electronic components when they are shut off abruptly. If a MOSFET were being used to switch the washer pump, I'd say that you would want to put a flyback diode in the circuit to protect the circuit.

Can't tell if the LVD proposed has internal flyback diodes. Maybe, maybe not depending on whether they designed it to handle inductive loads. You could easily add your own externally.

For $8 - can't go wrong even it it eventually dies from an inductive load. At that point you could switch to a MOSFET switch like this for around the same cost and is even smaller:

https://www.amazon.com/ANMBEST-High-Power-A...-spons&th=1

Don't think that one will work. It switches gnd but not vcc. I need the other way round. There is a question and couple reviews about it.

I looked at mosfet circuits but the potential for a plug-n-play solution for <$8 seemed a no brainer. I found a couple DIY circuits that look very similar to this module when built. They both used flyback diodes. Hoping this does the same. I think I spy at least 3 diodes in the pics on Amazon. Can't say for sure.

[Spoke]

Now that I've had some time to think about the LVD solution here are some thoughts.

I think the same overall goal of disconnecting the pump ground path from the intermittent relay could be achieved with a simple MOSFET transistor. The control input to the MOSFET gate would be the 12v input from Black/Brown stalk switch,

I can't tell from the specs for the proposed LDV if it can handle inductive loads or is just for resistive load like a light, LED, or battery.

Inductive loads (relays, motors) can generate voltage spikes that will damage electronic components when they are shut off abruptly. If a MOSFET were being used to switch the washer pump, I'd say that you would want to put a flyback diode in the circuit to protect the circuit.

Can't tell if the LVD proposed has internal flyback diodes. Maybe, maybe not depending on whether they designed it to handle inductive loads. You could easily add your own externally.

For $8 - can't go wrong even it it eventually dies from an inductive load. At that point you could switch to a MOSFET switch like this for around the same cost and is even smaller:

https://www.amazon.com/ANMBEST-High-Power-A...-spons&th=1

Don't think that one will work. It switches gnd but not vcc. I need the other way round. There is a question and couple reviews about it.

I looked at mosfet circuits but the potential for a plug-n-play solution for <$8 seemed a no brainer. I found a couple DIY circuits that look very similar to this module when built. They both used flyback diodes. Hoping this does the same. I think I spy at least 3 diodes in the pics on Amazon. Can't say for sure.

@bbrock

I think I agree with you about the switching. The intermittent relay only functions in the J position when S1 is open. Thus grounding pin S on the relay will disable it. This is why tapping the washer motor on S1 to ground disabled the relay.

Therefore it can be assumed that the input pin S on the relay has an internal pull-up circuit to activate it when the net connected to pin S is open circuited and pin S voltage will float upwards to some positive voltage. Is this the voltage you measured or was going to measure?

If pin S does float upwards then putting a FET input on pin S will likely turn on the washer when the intermittent relay is active (in J position).

[bbrock]

I think I agree with you about the switching. The intermittent relay only functions in the J position when S1 is open. Thus grounding pin S on the relay will disable it. This is why tapping the washer motor on S1 to ground disabled the relay.

Therefore it can be assumed that the input pin S on the relay has an internal pull-up circuit to activate it when the net connected to pin S is open circuited and pin S voltage will float upwards to some positive voltage. Is this the voltage you measured or was going to measure?

Yes, but the voltage readings are small. In the J position with the washer disconnected, I read ~4-11mV which cycles repeatedly. I didn't time the cycles but they seemed like they might be about what the wiper intervals are. Does that sound right?

If pin S does float upwards then putting a FET input on pin S will likely turn on the washer when the intermittent relay is active (in J position).

This sounds interesting except I don't want the washer to run in the J position. Washer should run only in P position and only the intermittent relay should run in J position.

I shouldn't have called this a "simple" circuit before. I should have called it a German circuit. Simple in design but complex in function. (IMG:style_emoticons/default/lol-2.gif)

[Spoke]

Yes, but the voltage readings are small. In the J position with the washer disconnected, I read ~4-11mV which cycles repeatedly. I didn't time the cycles but they seemed like they might be about what the wiper intervals are. Does that sound right?

I would think there would be more voltage deflection than a couple of millivolts. Assuming you had it on DC mode. I wonder what the AC mode would read. If this were a voltage ramp you might get different reading on AC mode.

This is good though because the FET circuit may not have enough resistance to ground to inhibit the intermittent relay and there's not enough voltage to turn the FET on.

[bbrock]

Yes, but the voltage readings are small. In the J position with the washer disconnected, I read ~4-11mV which cycles repeatedly. I didn't time the cycles but they seemed like they might be about what the wiper intervals are. Does that sound right?

I would think there would be more voltage deflection than a couple of millivolts. Assuming you had it on DC mode. I wonder what the AC mode would read. If this were a voltage ramp you might get different reading on AC mode.

This is good though because the FET circuit may not have enough resistance to ground to inhibit the intermittent relay and there's not enough voltage to turn the FET on.

Yeah, I just wrote those readings off as noise. I didn't think to measure AC. the relay is kind of a pain to get to with the charcoal canister in place, but next time I'm in there, I'll see if I can get some AC readings.