28 replies to this topic

[Ethel]

If there are only 2 wires coming out of the motor then it's single speed, unless one has been cut or broken off.

[mccand]

I am now even thinking that if I do need a new switch and a new motor, then I may as well get a 2-speed switch, and then it would just be a matter of running a blue-green wire from the 2-speed switch to the open spot on my motor plug harness to actually have 2-speed capability?

(If I'm gonna do all the work, may as well get an upgrade out of it!)

[Ethel]

not sure where you did your continuity checks. If the switch is ok (test it unplugged to avoid confusion) then in the off position the terminals for red/green & brown/green will be connected and in the on position red/green connects to green. The remaining terminal should be isolated in each case.

A quick "how it works" may help:

When you turn the wipers on the, green, ign live is connected to the red/green which supplies the motor windings. When you turn the wipers off current flows from the green live at the motor connector block, via the park switch, down the brown/green to the wiper switch on the dash and back up the red/green to the motor. It stops running when the park switch opens, breaking the contact with the ignition live and making contact with earth to drain any residual current from the motor windings.

It could be useful to test continuity around the parked motor with the ignition off. The green should be isolated and there should be continuity between the red/brown and earth.

I don't think you'll find a suitable twinspeed switch to replace the one you have. It could be entertaining working out a circuit though - maybe use the original as a fast slow changeover and put an on/off/wash&wipe in place of the washer pump or on the column?

[SolarB]

I fitted a two speed wiper motor to my '72 car. Use a headlight switch (these are double throw) but replace the front of the switch with the front off the original wiper switch.

Bingo! Two speeds and originality in the cabin.

[mccand]

Isn't this what I would need?
http://www.minimania...4/InvDetail.cfm
And is it true that all I would need to do is run one wire from the switch to the motor as I described above?

As for how I measured the continuity, I checked at both the wiper motor harness and the switch. With the switch off, it is not connecting the red / green to brown/green like it should. I do think the switch is shot.

My problem now is trying to figure out why, when the park switch is engaged, the fuse is blowing. I will run the test you suggest & let you know the outcome. Thank you for the layman's terms of how it works. This is helpful. Somehow in the operation of the park switch opening the circuit, it is apparently shorting a +12V to ground.

Ethel, for your suggestion, I take it you mean do this with the harness plugged into the motor, correct? And when you say green should be isolated, you mean isolated from earth, correct? (and I will to it all with the park switch engaged, and the ignition off; otherwise fuse will blow.)

Thanks! (And SolarB- clever!)

[mccand]

Well, I'll tell you what I've found, and I hope you can help me interpret.

First of all, I confirmed that my switch is NOT connecting red/green to brown/green in the off position. It leaves them open.

Now, as for the continuity with the ignition off (and battery disconnected), I determined that:

With the harness PLUGGED INTO THE MOTOR, park switch in the PARKED or UNPARKED, and whether the dash switch is ON or OFF, the following is true:
1) The green wire (measured at the dash switch) has continuity to ground (bad I think).
2) The brown/green has continuity to ground.

AND

With the harness UNPLUGGED FROM THE MOTOR, (and independent of park switch position since unplugged),
A) With Dash switch ON,

1) The green wire has continuity to ground (as measured both at the dash and at the motor plug

2) The Brown/Green wire has NO continuity to ground.

B) With Dash switch OFF,

1) The green wire has continuity to ground

2) The Brown/Green wire ALSO has continuity to ground.

Lastly, the only time the fuse blows is when the ignition is on, and the park switch is in "park" position. This is certainly true when the dash switch is off, and I do not know if it is true or not when the dash switch is on, since it moves out of the way fast enough that I don't think the fuse has enough time to blow. (what is true is that if the wipers are on, they work, so either the fuse does not have excessive current when the dash switch is on & it is passing through the park position, or it *does* but it passes through so briefly that it does not have enough time to blow.)

So what does all this mean? Well, for one, my switch is not working properly (but in a way it is a good thing, b/c if it were working properly, the wipers would go home the minute I turned them off rather than stay where they are, and the fuse would promptly blow once it got "home").

Secondly, I *think* that the fact that the green wire has continuity to ground at all times is bad. (?) I am not sure of this, and I am not sure what to do about it. Do I run a new green wire from the switch to the motor? (I did check, and it has continuity to ground in both locations, indicating to me that maybe the green wire has a short to ground between the switch and the motor plug). The flaw in my mind with this argument is that if this were the case, wouldn't the fuse blow at all times, as I understand (and measured) that the green wire gets +12V the moment the ignition is turned on(?)

HELP!!!

[SolarB]

Isn't this what I would need?
http://www.minimania...4/InvDetail.cfm

$54.95!!!!

I think this is what you need. Linky Still expensive though.

[GraemeC]

Just to get things straight in my head:
You have a rocker switch mounted in the centre switch panel
It has blade type connectors on the rear - are the connecting wires on individual female blades or a multiplug?
You have Green, Red/Green and Brown/Green wires on the rear of the switch - any more? Any un-used terminals?

[mccand]

Just to get things straight in my head:
You have a rocker switch mounted in the centre switch panel
It has blade type connectors on the rear - are the connecting wires on individual female blades or a multiplug?
You have Green, Red/Green and Brown/Green wires on the rear of the switch - any more? Any un-used terminals?

Yes, rocker switch in center switch panel, blade-type connectors, individual female blades, green, red/green, and brown / green wires in the rear, no more, no unused terminals.

Looks like this:

<http://www.gbcarpart...rSwitch13H6343>

Any thoughts on the continuity of the green to ground?! (as measured both at the rear of the dash switch, and at the plug that goes to the motor, whether the plug to the motor is plugged in or not..?

My thoughts are that if the green wire *does* go from the dash switch to the motor plug directly (a big if-- I don't know this to be true), and both ends have a short to ground, then that means the green wire must be shorted to ground somewhere in-between..? But what I cannot explain (if this is true) is why the fuse would not blow instantly no matter what if the plug at the motor harness is plugged in. So I think my thinking is flawed, but would really appreciate any thoughts!

Cheers,

-Greg

[mccand]

I was thinking about this last night as I was trying to sleep... I don't know about this grounded green wire business... but what I *do* know is that when the park switch (which is new in my car) is doing its thing and shorting the motor windings to ground through the brn/grn wire, the fuse is blowing. So is it fair to assume that the motor windings have some sort of internal short of +12V, and when the park switch grounds the motor, the fuse blows?

This tells me that I need a new motor, and I already know I need a new switch. And I could take this opportunity to get a 2-speed switch, and run the extra wire from there to the motor for an upgrade.

This does not explain my green wire continuity to ground issue, but the reality is that issue is not causing my fuse to blow for some reason.

Any counter-arguments to my line of reasoning above? (not cheap, so I'd like some confirmation if at all possible!!)

Cheers!

[GraemeC]

I think the Green having a reading to ground may be a red herring at this stage as if it were a problem your fuse should blow constantly.

Have you check the continuity between the terminals of the switch when the switch is disconnected - just to map out its internals and ensure the wires are plugged into the right places?
With the switch off you should have two terminals connected and one independant. With the switch on you should have a different pair of terminals and one independant.

I don't think the motor is shorting to 12V as this would be an unusual fault. Plus the park switcc doesn't ground the motor, it simply connects the Brown/Green to ground (the motor will always be ground).
It is more likely that the Brown/Green is being fed with 12V and the park switch is then connecting this to ground.

[Ethel]

Good finds on the switches The problem with using a headlight switch (I think) is that it switches sides and mainbeam on together whereas your wipers should be either one or two speeds. Can't see how it would park either - but sometimes you can mix 'n match the bits to get different effects.

Back to the original topic...

The wiper supply is ignition dependent so, with the ignition and wipers switched off the green wire should be isolated from everything. But note there are other ignition dependent components that can provide a ground - chiefly the alternator.


gnd_____Alt'r ___
+ve____ign sw__l___wipe sw_/ __park sw_/ __
--------------------- L______________________l



Graeme makes sense, if you have individual spades on the dash switch that seems the most likely spot for confusion. However the park switch does switch to earth - by doing so it grounds both sides of the motor windings so it stops dead, otherwise the residual current (the motor is also a resistor: with a potential difference across it) could turn the motor enough to reconnect the contacts in the park switch.

Park
Wipe
+ve

Your dash switch should be as above - connecting either the top or bottom pair when flicked.

[mccand]

I get it!!! Jeez, I am slow. The final clue was the description of the switch immediately above (Ethel). THANK YOU! My switch is fine, it was just wired incorrectly, and I was measuring at the terminals where the wires were, never really considering that the wires might have been in the wring spot. After all this, I *believe* (strongly believe) that my problem is that the green wire was in the middle (in the picture that Ethel drew above). So the motor did not get the signal to park when off, and when it happened to be in the "park" spot, it would short (when off). Of course, I am figuring this out after I already burned out my last fuse (of about 20!).

Believe it or not, while I am clearly not an electrical engineer, I just finished installing a stereo (may be blasphemous for some). I have the head unit under the heater, and used the speaker pods in front and 6 x 9's under rear seat from custom consoles, and a big amp in the trunk (to be mounted to the rear seat back). Was working great last night (first time), but of course I can't play with it tonight because it's the same damned fuse! Argh!

But I will sleep well, confident that that small wiring issue was the whole problem. (well, I sure hope so!). Thanks so much for your help. I really made this harder than it should have been; I should have considered more carefully the switch wire locations!

[mccand]

Confirmed- the wiring to the back of the switch was the problem. It actually parks and stops when I shut off the wipers, and it doesn't blow a fuse. I like to think that I averted a more difficult diagnosis by replacing the brn/grn wire, (which did have some exposed copper), and that the new park switch I bought to try to solve this was good preventative maintenance... Anywho, at least I didn't shell out for a new motor or switch. Thanks, all. Time to play with the stereo!