Windshield Wipers worked fine. Then suddenly didn't. Reading indicates Switch tends to be a suspect. But something odd going on. Looking at Diagram and should be getting power at Light green Wire at the switch connector with car switched on. Only I'm not. I'm getting power on a Green and Black wire and nothing on the Light Green. Keep in mind this is the connector, not switch side. Getting weird readings at the fuse too. Fuse #6 should have 12 V with car switched to On/Acc. Except I'm getting nothing there on my Multimeter. Except the Fans are working which also run off fuse #6. (And I know this is good because of extensive work I did on the fans not long ago).

I've checked Grounds and cleaned them all up and new fuse #6 and cleaned and closed the prongs on #6.

Vexed.....

I'm kind of thinking the Motor maybe has a fault, but that wouldn't explain the pre-switch weirdness. Ideas?

 

So one mystery solved? There's an 8 pin connector and only 7 of the pins are used (at least on the diagram). S57 Diagram says the LG wire carries power and does not reference a Green with Black tracer wire (GB). In my case, the green carries nothing and the unreferenced Green/Black carries the voltage. Since the Wipers were working and the Green/Black is carrying voltage I have to assume that this is how it should be.

 

So as part of this I read that it is possible that the motor could be rusted up. So I was in there and thought I would test it. I tried all the contacts but nothing made the motor turn so I thought it might have packed up. Anyway, disassembled it and tried to test but couldn't figure out where to apply power and negative to test it. Found this useful picture from an MGB forum:



Saved here for posterity. So if you apply power to the red or yellow and negative to the blue the motor should turn. Quick and easy way to test the motor.

Still haven't fixed the Wipers... But looking like it must be the switch.

 

So I've figured out the mystery of the the Light Green with Black tracer wire. This is for the washer. Which is working.

I have pulled the switch and it works properly. I tested all the wires for continuity and they are all good. I then tested the switch's positions for continuity and they all work too.

Mystery seems to be why I am not getting power at fuse 6 and hence to the green wire, which I am now dead certain isn't getting any power. Now, I got thrown and am thrown by the fact that the climate control blower runs off the same fuse 6. With car ignition in ACC position, fan works on defrost. Last I drove it, it worked fine while driving as well. But there is definitely no power to fuse 6. What is before that? Load relay?

Any ideas?

 

Update. Tested the power to the load relay. Going in there. Far as I can see there is nothing between the Load Relay and Fuse #6. So I think this has to be the load relay. Gotta test it.

 

Thins it is the load relay gone bad. Can make it do anything on test. Does anyone know what the p/n is for this? It has a 30/51, 87, 86 and 85.

 

I've tested the load relay and it is bad. This relay is a Lucas SRB402. It is 12V 20A. It is frequently being replaced today with a 12v 20/30 amp SRB502.

I have on hand a VW Relay with the same pins, well not quite the same it is 30, 87,86 and 85. Diagram looks the same, But it is 12v 40A. Anyone think it will work?

 

It should be fine. The "30/51" designation is a bit arcane; most relays today simply say "30". You could also use one with 30/85/86/87/87A pins.....with the "87A" pin simply left unused.

However......

On your VW relay check that it doesn't have a diode...which should show in the diagram. Most don't, some do.

Cheers
DD

 

Damn @Doug that was a hell of a catch!! The VW relay does have a diode, at least that is what I think is on the diagram. Smaller rectangle below the larger rectangle with the diagonal line? What's the significance of the diode?

Also, do you know of a generic replacement for this Lucas Relay? Like something I can pick up at the auto parts store?

It seems the Lucas SRB520 has superceded the earlier SRB402. This page lists equivalents, but all I have found are European. The Durite would be great at 4.00 pounds except Durite doesn't seem to exist in USA. I've located a Volvo Penta but it is $22.00.

 

The symbol for a diode looks like an arrowhead. It's a one-way valve, so to speak....allowing current flow in just direction

I think what you've described is a resistor symbol. What effect it has depends on what branch of the circuit it is on. I doubt that any harm would come from trying it.

You can use a generic "Bosch style" or "Ice Cube" relay from any local auto parts store. They're ubiquitous; used for a million different things

For example:

https://www.summitracing.com/parts/b...9150?rrec=true

Cheers
DD

 

A whiie back, I was installing relays. Just getting the hang of how they worked . I found a "kit" . to install driving lights. Goo d deal at the local parts place. Works great.

Or Google "Buelhler". High grade units. My son uses them on sale with his accessory E Fan kits.

My Jaguar ahs a couple. on the cowl.

Carl

 

Thanks for original post!! My #6 fuse showed no juice so pulled the ignition protection relay and tested. No go..until I banged it on the table a couple times. Then seemed to work 😂

But I had a couple spares from a recent junkyard strip of an 87 and one of those tested good without banging

Now I have power at #6 and ensured power at motor plug hi/low terminals. Woo hoo!

Just gotta clean up motor and reinstall and now I can drive in the rain..which ironically I try to never do..but now I can at least clean my windshield

Also since this load relay drives #5 too my rear window defrost wires should work. Will let you know 6-7 monyhs from now

Randy