Wiring Woes

[vping]

So the B is running but I have some wiring issues. I checked out all of the electrics when I got the car and with the exception of the Reverse light being on all the time, everthing worked. I assume a stuck switch. Hazzards, signals, heater...even the interior and trunk lights - all worked.

The motor and trans were pulled, old trans removed and an OD joined up with original motor. Back in the car and here is where I am at.

All lights are on but Signals don't work & reverse lights do not come on. The strange thing is that when you put it in any gear, 'cept reverse, the RH front & rear signal come on. There also is no power from the yellow wire coming from the Washer stalk so it is not sending power to the OD.

 

[piman]

Hello vping,

sounds like a couple of crossed wires. I would check carefully all the connections you have remade after re-installation of the power unit.

After that it is out with the meter and start tracing.

Alec

 

[Kimberly]

Make yourself a couple of enlarged copies of the wiring diagram, one for reference and one to mark off sections as you have checked the wiring with a meter. Don't forget to check the ground connections. Clean each connection as you check it and use dielectric grease to prevent future corrosion.

 

[vping]

Started doing that yesterday and as simple as the wiring diagrams are I'm still stumped. There are only four wires coming from the trans.

Green - ?
Yellow - I Assume OD
Light Green with either white or yellow line - ?
Green with Brown or Pink - ?

Not sure what part of the trans these come from. Any guesses?

 

[Adam58]

Hi Vince,

I have a copy of Rick Astley's "MGB Electrical Systems." It's awesome! According to that reference, those wires are as follows:

Green - Reverse light SW(and MANY other things)

Yellow - I Assume OD - YES (one side of the OD lockout switch on the trans.)

Light Green with either white or yellow line - G/W = RH flasher (Are you sure it's coming from the tranny as this may explain what you are seeing!) LG/W = Seatbelt sensor. I don't see a reference to G/Y or LG/Y.

Green with Brown or Pink - Other side of reverse light SW

Yellow s/b hot from the column SW when it's ON as you suggested. It goes to the OD lockout SW on the trans. There is a Yellow/Purple wire (maybe loose, rather than in the loom) in series between the the OD lockout and the OD solenoid. (The other side of the solenoid is internally grounded)

Good luck! If all else fails, but the book - you won't be sorry!

Adam

 

[vping]

I will be looking into this book. Right now I am looking at Haynes and a color copy of the Bentley.

I pretty sure. If you look at the pic, you can see where they go into the loom and then down towards the trans. Ah but maybe it connects somewhere near the bellhousing and then onto another harness and onward to the RH Flasher.

G from "trans area" I connected to green in harness. Makes sense?

LG/W - There is not a matching wire coming from the harness. In fact I do not see any LG wires.

G/B - There is not a matching wire coming from the harness although if you look at the bottom of the photo, you will see a solo connector with a Green/Brown wire. The stripe on the G/B coming from the "trans area" is lighter which is why I refered to it as "pink. Could these go together? The wire I refer to as G/B is the left most wire with arrow.

Y from trans I can connect to yellow in the main harness. I suppose the Yellow from the harness is coming from the stalk. If I pull the stalk towards the rear it should then be "hot" when the test light is applied. If not, there is one potential problem.

I have one extra wire coming from the harness. It is a Yellow with Orange stripe. Not sure what this should connect to.

Am I making sense in describing this?

 

[vping]

To add to my last post I ask this.
Are all 1974 Stalks alike? The car did not originally have OD. Do I need to take the stalk from the donar car? Are Midget & B wiper stalks the same?

 

[vping]

So I did some research and found some pics from the Donor car.

Yellow to yellow - OD
Green to green
Light green/White to Yellow/Red - Reverse switch.
Green/Brown to Green Brown

Whether or not this makes sense should I try it?

 

[68Sprite]

I agree with Adam, Rick Astleys book is a must have for any MGB owner. Also you can get laminated wiring diagrams from Prospero's Garage https://www.slash5.com they are alot bigger and in color.

 

[Wray]

All 70's MGBs had the OD switch on the wiper stalk whether the car was fitted with OD or not.

 

[vping]

OK I'm doing better. All wires from the Trans harness are connected based on what I can see from the original pics of this car and the donor car. This I believe to be correct.

Yellow to yellow - OD
Green to green
Light green/White to Yellow/Red - Reverse switch.
Green/Brown to Green Brown

The brake lights come on when I depress the pedal.
The hazzards work.
The lights don't come on anymore when I put it in gear.

The reverse lights do not come on. On all the time before.
The signals do not come on. Worked before

<u>Wires still not connected are:</u>

Under hood.
1 White/Black in the main harness where other harnesses merge. Pictured in previous post.

Under console
1 White/Black which I beleive is for a rear def.
2 Brown/Purple - in a double connector and which should be for the Seatbelt lamp & buzzer. Disconnected for a reason DPO.
2 Green - in a double connector.
2 Purple/Green - in a double connector.

I need to know where these go and I should be done with the wiring.

This all started becuase we had it up on jacks and while it was running and in 3rd we engaged the OD but the RPMS did not drop. IIFC during our initial testing, when the switch is pulled back, and using a test light, the yellow is not hot so I need to figure out why I do not have power to this as well.

 

[Kimberly]

I will be looking into this book. Right now I am looking at Haynes and a color copy of the Bentley.

I pretty sure. If you look at the pic, you can see where they go into the loom and then down towards the trans. Ah but maybe it connects somewhere near the bellhousing and then onto another harness and onward to the RH Flasher.

G from "trans area" I connected to green in harness. Makes sense?

LG/W - There is not a matching wire coming from the harness. In fact I do not see any LG wires.

G/B - There is not a matching wire coming from the harness although if you look at the bottom of the photo, you will see a solo connector with a Green/Brown wire. The stripe on the G/B coming from the "trans area" is lighter which is why I refered to it as "pink. Could these go together? The wire I refer to as G/B is the left most wire with arrow.

Y from trans I can connect to yellow in the main harness. I suppose the Yellow from the harness is coming from the stalk. If I pull the stalk towards the rear it should then be "hot" when the test light is applied. If not, there is one potential problem.

I have one extra wire coming from the harness. It is a Yellow with Orange stripe. Not sure what this should connect to.

Am I making sense in describing this?

Don't use the Haynes diagrams. Haynes combines too many years into one diagram and some of them have errors. Make yourself a couple of enlarged copies of the correct diagram from Dan Masters' site, https://www.advanceautowire.com click on stock schematics. I made myself a copy on four sheets of 8.5x11" paper and taped the pages together. The size of the diagram is about 15x20".
Look at the diagram, you will notice that yellow wires do not connect to green wires. Look at the components and see what color the wires are that are connect to them.
Before condemning the stalk switch, did you test the input (white wire) and output (yellow wire) of the switch.

For everyone else that has a copy of the diagrams from Advance Auto Wire. Dan made corrections to the file about two weeks ago.

 

[vping]

Kim,
Thanks. I've been using the 1973-1974 3NB067 diagram but I just noticed that there is a 1973-1974 5NB056 diagram as well and they are way different. I did not test the input of the switch. Just the output which was not hot.

 

[Kimberly]

OK I'm doing better. All wires from the Trans harness are connected based on what I can see from the original pics of this car and the donor car. This I believe to be correct.

Yellow to yellow - OD
Green to green
Light green/White to Yellow/Red - Reverse switch.
Green/Brown to Green Brown

The brake lights come on when I depress the pedal.
The hazzards work.
The lights don't come on anymore when I put it in gear.

The reverse lights do not come on. On all the time before.
The signals do not come on. Worked before

<u>Wires still not connected are:</u>

Under hood.
1 White/Black in the main harness where other harnesses merge. Pictured in previous post.

Under console
1 White/Black which I beleive is for a rear def.
2 Brown/Purple - in a double connector and which should be for the Seatbelt lamp & buzzer. Disconnected for a reason DPO.
2 Green - in a double connector.
2 Purple/Green - in a double connector.

I need to know where these go and I should be done with the wiring.

This all started becuase we had it up on jacks and while it was running and in 3rd we engaged the OD but the RPMS did not drop. IIFC during our initial testing, when the switch is pulled back, and using a test light, the yellow is not hot so I need to figure out why I do not have power to this as well.

Have you looked at the wiring diagram? The reverse switch does not have a yellow wire going to it. The reverse switch has a solid green wire connected to it and a green/brown wire from the bulbs connected to it. Don't guess what the wires are for. Look to see where the wires originate and use a meter to test for power. Having the wiring connected wrong to the overdrive can ruin it.

 

[vping]

Yes I have and still and not sure which I should be looking at. There are two switches on the 4 speed and I am not sure whch is which. How many switches were on the OD I cannot remember. The 4 speed has a light green/brown? wire and a solid green wire hooked to a small switch. The larger switch - more forward had Green/brown and green. The green join somewhere in this mini harness and go up the firawall towards the main harness. The OD has the same wiring with the addition of the Yellow.
I was only hooking up wires based on the photos of how they were hooked up before I took it apart.

Here is the before pics. Old rusty is the donor with the OD wire. The other is the 4 speed minus OD wire. You can clearly see how they were run.

 

[Kimberly]

With the wires disconnected from the two switches on the transmission, set your multimeter to measure continuity. With the transmission in reverse gear one switch should have continuity and the other shouldn't. The one with continuity is the reverse light switch. Now put the transmission in fourth gear and check the continuity of the two switches. The one that has continuity should be the transmission interlock switch.

Now look at the wiring diagram to see what color wires are connected to the reverse light switch and use a meter to confirm they are connected properly. Does your car, not the donor car, have the seatbelt interlock system?

 

[vping]

Can't I do a continuity test up on top and not have to get under the car? There is no way for my hands to fit up into the tunnell and disconnect the switch on hte left side of the trans.

 

[vping]

Oh and to answer the 2nd question I think I do have the interlock system. There are (to my best rememberance) 3 switches on the Transmission. Maybe lets define those so we can speak the same language.

If you are standing over the transmission looking down at it and both the transmisison and youself are pointing forward, there is a little switch on the left side of the upper part of the trans pointing sideways left. I think this is the Reverse switch and has a Light green wire and a dark green wire. About 6" forward but down a little is a large switch which is the OD Isolation switch? It has a green/brown wire and a geren wire. Lastly there is a third switch which if I remember correctly is similar to the 2nd switch but this has the Yellow wire attached so I assume this is the Interlock switch.

If I am wrong on any of this please let me know. I want to familiarize myself with the switch names and then I can start to determine where they go. To the best of my knowledge the Trans wiring is correct because I never took the wiring off of it while transferring it from car to car.