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.

[Spoke]

Sounds like the intermittent relay needs a couple of volts to engage. If 2 diodes work then fantastic. The 1N4001 may be ok to use as the motor may not draw that much current. Also as you get higher current diodes the diode needs more current to get the same voltage drop so a larger diode may not work well.

You are correct about Schottky diodes; they have much lower ON voltage and not well suited for your application.

[bbrock]

Sounds like the intermittent relay needs a couple of volts to engage. If 2 diodes work then fantastic. The 1N4001 may be ok to use as the motor may not draw that much current. Also as you get higher current diodes the diode needs more current to get the same voltage drop so a larger diode may not work well.

You are correct about Schottky diodes; they have much lower ON voltage and not well suited for your application.

@Spoke

Oh right. I guess the "groan" I heard with only one diode was relay chatter and as long as the relay gets enough voltage to latch, it will be fine. I was worried about under voltage on the wiper motor and had forgotten about the relay. I confirmed that 3 diodes still work but seems to not be necessary.

I measured 4.4 amps draw on the washer motor which was higher than I expected, but in line with what I could find for similar washer pumps online. I noticed the 1N4001s were warm after running intermittent for a few minutes, which is what prompted rechecking the specs. I'm thinking these BY880-50 diodes might be a good way to go. Same "ON" voltage but rated for 8A, or would 5A diodes like the BY550-100 be a better choice?