My windshield washer pump, front and rear, hasn't worked for quite a while. It was determined that the problem is at the BCM. I'm not replacing the BCM, so I'm looking for some guidance in wiring the pump directly to a momentary push button. I plan was to run a wire off the cigarette lighter (via piggyback fuse) to the positive side of the switch, run a wire from the negative side of the switch to the positive side of the motor and then ground the negative side of the motor.

Here are my questions: Which is the positive? How do I ensure that the front sprayer is the only one that operates?

 

Bump.

 

If you're disconnecting the pump completely and rewiring to a new dedicated switch then it couldn't possibly control the rear pump (I assume that there are separate pumps for the front and back).

Which ever terminal has continuity to ground is your ground. Any multimeter can check this.

 

It's the same pump for front and back, that's why I'm not sure how to go about it.

 

good news .. here's the diagram



bad news ... like so much on the MINI it is damn complicated

38 is the motor in question, and yes one motor drives both front and rear washers

39 and 40 are relays for front and rear respectively. Allegedly these control the direction the pump spins sending fluid front or back .... located behind driver kick panel ...

37 is the switch

14 the GCU

********************

it would be easier to just "remove" the existing pump .... buy one for a classic Mini ... http://www.minimania.com/part/GWW125...asher-Electric .. which has a simple +/- set of electric contacts. Run a button and a fuse and reroute the hoses ... done.



you could even go more old school and use the manual pump from an older Mini .... you just need longer hoses .... http://www.minimania.com/part/GWW102...-Midget---Mini

 

I've seen that diagram, but since I'm bypassing all that with my own wiring, it didn't really tell me much about the route I want to go with this. The only thing i got from it, and I'm assuming you're alluding to the same thing, is that there's no way to control the pump direction without the relays. Perhaps I can use simpler pump from another vehicle.

 

The relays just reverse the polarity that the pump sees. If you never reverse the polarity (by not using the relays) the pump will alway spin the the same direction and only send the fluid to the front.

 

how about a 6 pole, 3 position, center off switch ..... you just swap polarity with the two positions ....



in olden days I'd just go to radio shack for this ....

you could get the same result with two pushbuttons .... they should be two pole tho so the ground runs tru them ....

 

Let me just say that I have not look into the Mini front/back washer pump sharing. If this is true that only raise my appreciation of how advanced the design was for a car developed circa 1999. Designing for economy is much harder than specifying the fanciest parts and the most complicated contraptions that cost is no object.

I would be careful with the two push bottom suggestion for - idiot proof reasons. My favorite saying is you can try designing for idiot proof, but they can always make better idiots. What prevent someone pushing both buttons simultaneously?

To the OP, have you exhausted to properly troubleshoot the BCM without breaking the bank?

 

I would be careful with the two push bottom suggestion for - idiot proof reasons.

oh yes .... there are issues in both ideas. I kept the descriptions simple

I'd not install without some fuses .... and real electrical engineer could give us a good 'two push button' version that didn't blow things up!

 

I believe that is actually a double pole - double throw switch (DPDT) switch.

 

Believe me, I'd rather not have a random button to control the washer pump, it's, without a doubt, the BCM. I'm probably going to go with a single button that just activates the front washer and I should have time to tackle it this weekend.

 

On a Vette there is a place in Maryland that rebuilds the door/window modules but I don't know if there are places that do the Mini, but, below is an article on fixing the BCM and you will note that the wiper motor ground is mentioned.

https://gethypoxic.com/blogs/technic...r-bcm-bc1-unit

 

I've seen that article, however it falls outside the boundaries of my skill level. As far as vehicle maintenance/repairs is concerned, electronics is my achilles heel.

 

I just had my motor and bottle out and there was a + marked on one side of the clip for that connector. Easiest way to do it would be like setting up aux lights. Small wires into the cab for the switch, and a large (ish) wire from the battery through a relay to the motor, then from the motor to the ground. Test it before buttoning up, and just attach the hose to whichever side the water comes out.

James

 

Ahh, I didn't even look at the clip for a +/-, thanks for the heads up. As for power, I'm going to run a piggyback fuse off of the cig lighter.

 

Where did you find this wire diagram that is all in one page?

I finally have time to consult my crappy Bentley, and you are correct in every detail. The Bentley schematic spans 10 pages though the shared pump (front and back) spans two (not counting the switch contacts in the wiper control stalk). Yup. Our Mini is one of the most advanced earlier fly-by-wire modern cars.

There are many things aside from the GCM that fail can lead one to assume the fault lies in the GCM. To properly diagnose do require systematically eliminating all the suspects. Having a helper would greatly help as it will require having one activating the wiper spray while another person check/monitor at another spot.

It is really not that complicated if you have some fundamental grasp of basic electronics. I would start with fuses, and then relays. I have seen relay failure that is very difficult to verify. They often fail from age and can behave perfectly good when you probe them with a DMM.

 

I am 100% sure, without any inkling of a doubt that it's the BCM.

 

 

The euros do tend to over design. To change a $20 oil pan gasket on my 928 you had to have a special jig to hold the front end together as you had to drop the front end to get to the oil pan. Best analogy I heard was the Howitzers in WW2. German gun had like 35 moving parts and was an "engineering" masterpiece. The American gun had something like 12, it was a "maintenance" masterpiece. Guess which gun fired more shells on a consistent basis?

 

Assuming OP did indeed accurately diagnosed that the fault lie with the BCM, there is a very simple and safe way to work around the defective BCM outputs with just a simple center off momentary SPDT toggle switch. You can retain the share pump arrangement and you would not even have to mess with adding in new fuses.

The two outputs from the BCM in the above diagram are what is known as open collector driver. When active each (only one and never both) acts like a switch shorting the signal to ground to complete the current to energize one of the two relays, depends on if you choose to wash the front, or the rear.

What you need to do is to have the SPDT switch substitute these two outputs. The pole (typically the center contact) of the switch is wired to ground, and the two throws substitute the two outputs of the BCM. Of course you should severe the connections to the BCM.

This is just an idea so I caution that you double check and understand the schematic before proceeding.

 

With everything that I serviced on the Mini, it is complicated and hard is because the packaging into such small car and still have a huge interior volume. The complex washer arrangement is likewise due to the concessions made over two separate pumps and reservoirs.

 

I wish you lived closer! Like I stated previously, I'm a dumb @ss when it comes to this kind of thing. Your post sounds great, but it may as well be written in Chinese.

 

Don't tempt me. The fact is I can write in ..., though with some difficulty.

對不起. 你的迷小谷巴有麻煩.

Little Mini is 迷你小車

Cooper is 谷巴

Cooper is affectionately referred to as 小谷巴 - little Cooper.