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.

[bbrock]

Well that escalated quickly (IMG:style_emoticons/default/blink.gif)
The new VDO pump came yesterday so this morning I went out to the garage just like last Saturday, thinking I'd spend 15 minutes tops swapping out the windscreen pumps and declare victory on this project. Two hours later I had this:





So what happened? (IMG:style_emoticons/default/confused24.gif) Well, when I installed the new pump, it wouldn't engage pulling back on the wiper lever. More curious, the flick wipe feature was being reluctant too. I pulled the pump and hooked it up to my power supply and couldn't get it to run. I knew it was unlikely both the URO and new pump were bad, so I did what anyone with half a brain would have done last week - hook it directly to the battery. Yep, fired right up. Grabbed the URO pump and did the same. Yep, works fine. Turns out my cheap power supply just wasn't pumping enough amps to get the pumps going. Could have saved $50 had I done that last weekend. However, the VDO pump is much quieter than the URO. The URO screams so loud, it made me jump a couple times when I used it while driving. So I'm not that upset I bought the VDO. Anyway, so what the hell?

I unhooked the pump and checked voltage on the end of the brwn/blk wire again. 12v when the lever was pulled. Hooked the pump back up. Less than 1v. Hmmm. (IMG:style_emoticons/default/idea.gif) I cut open the brwn/blk wire so I could bypass the diodes to rule them out. Same results. I cut the diodes out completely just to make sure they weren't draining power somehow. Nope, same thing. I had an idea of what might be happening but continued to troubleshoot everything in the fuel compartment before acting on my hunch. Ground was good. Everything was connected correctly and working fine as long as the pump wasn't connected. Okay, time to pull the wiper switch.

I swear I took a pic of the switch inside the wiper control assembly but apparently not. Anyway, it is easy to see and is part of the same mechanism that pushes the plunger on the valve for the pneumatic washer gizmo. When the switch is in zero position and the lever is pulled back, there should be zero resistant between the terminals that connect to the red/blk and brwn/blk wires on the harness. I was getting varying resistance values, but always resistance. Then on the harness side, I connected a very small gauge jumper between the same wires on the connector socket on the harness and turned on the key. Flick wipers ran. Now I connected the pump and tried again. The little jumper got hot as hell and I yanked it. So my hunch was correct. The switch in the wiper assembly isn't rated for the amperage needed to start those pumps. I figured I'd probably fried the switch but I have spares so wasn't worried. On close inspection, it made more sense. There was a spot of carbon on the contact of the switch. Apparently running the pump directly off that switch was causing it to spark and build up carbon until the resistance was too high to flow enough current. After cleaning off the contact with a little 1000 grit polishing paper and a spray with contact cleaner, I was consistently getting 0 ohms resistance with the lever pulled back.

The solution, of course, was to add a relay so I grabbed the relay that came with the Car Magic kit and set about designing the circuit. Where to get power and ground without running wires all over the place which is part of what I wanted to avoid? Everything I needed was right there in the intermittent relay socket which would make for a nice, compact install. Here's the fully functioning test circuit. Pretty, ain't it? (IMG:style_emoticons/default/biggrin.gif)



Let's fix up some connections to tidy things up. The relay coil still creates a path to ground, so I still needed the diodes to fully disconnect the brwn/blk wire for the intermittent function to work. Since the brwn/blk was now just switching on the relay, I went back to the 1N4001 diodes because they are smaller so easier to solder and shrink wrap. Then a couple pigtail connections to split power and ground off the intermittent relay. I also changed the wire from the relay to the pump to red/blk to reflect it is switched power. Here's the full spread of all the bits. This could easily be done up as a kit. I'm not doing it, but if anyone else wants to, please do.



After tidying things up with the new connectors, I gave everything another test to make sure all was working before putting the fuel compartment back together. Washers worked, flick wiper worked, intermittent wiper worked... and kept working. Intermittent wipers never turned off. WTF? That meant the brwn/blk wire wasn't grounded in positions 0-2 as it should be. As soon as I looked inside the car and saw the wiper switch assembly dangling on the harness, I knew what the deal was. You know that weird little copper tab on the wiper switch that gets lost and causes trouble? Yeah, that's where the brwn/blk wire connects to ground. Mystery solved. After putting the column switches back together, everything worked as it should. Only thing left was to button everything up. Here's what the final installation of the relay looks like. Very stealth and very factory looking. (IMG:style_emoticons/default/shades.gif)





I'll write up a how-to on this. Was it easier than installing the Car Magic kit? (IMG:style_emoticons/default/av-943.gif) Of course not. I like the install better though. Less drilling/molesting the car, less wire strung around, and everything is color matched to the factory scheme. It will also be a little cheaper and a LOT easier than the Car Magic kit for the next person. R&D can be a bitch. (IMG:style_emoticons/default/rolleyes.gif) Thanks to everyone for helping work through this project. It was really pretty fun.