Black/white wire in left side engine bay

[AarhusTr6]

Dear members/owners

Can anyone help me identify this black/white wire on the left side of engine bay?  Picture attached.  It has a round female end and is positive.

Ideas I have are brake oil after looking at the wiring diagram but I cant see any plugs for that anywhere.

Thanks

Richard

Edited November 3, 2018 by AarhusTr6

[john.r.davies]

This chart of "COMMONLY USED COLOUR CODES FOR BRITISH CAR WIRING"  from https://www.autoelectricsupplies.co.uk/cms/files/colour_code_for_vehicle_wiring_-_new_order_2.pdf says

"White/Black - Ignition coil contact breaker to distributor contact breaker; or distributor side of coil to voltage" 

Other sources agree, but if that is disconnected, how is your car running??

Has your DPO lashed uop some other connection?

JOhn

 

[AarhusTr6]

I am thinking PDWA wire?  But has someone plugged where the switch is?

Rich

[RobH]

The wiring schematic shows white/black being used for oil pressure and brake warning lamps - so perhaps that 4-way brake-pipe union should have a pressure switch instead of that plain bolt head, and this is the connection for it ?

( edit- I think you beat me to that Rich...)

Edited November 3, 2018 by RobH

[AarhusTr6]

Think I am on it.  . I got a box of bits with the car and it has what looks like a PDWA switch, but its a very differing connector than that on the wire.  I shorted the said B&W wire to ground and a lamp came on, on the dash so think I am onto something.  I believe it or not, really enjoy this stuff :-)

Rich

[ed_h]

The PDWA would normally have a switch Installed in it.  The switch has two male pins, but they are connected together internally.

Ed

[AarhusTr6]

Thanks Ed

So it seems I am missing the connector that goes on the wire, I cant find this listed anywhere, I guess I could improvise with two small female pins but would look ugly.

If I do put the PDWA switch back in, do I also need to bleed the brakes?

Rich

 

[Waldi]

Rich,

the pdwa consists of a small plunjer sealed with O-rings. One side sees front brake pressure, the other side rear brake pressure. If there is a large difference in pressure (for example as a leakage in a wheel cylinder, caliper or hose), the plunjer moves to the low pressure side. The plunjer is normally “in the middle”, since the front an rear brake system use the same pressure, although the systems are separated.

In the center of the plunjer is a groove, in which the switch lever sits. As the plunjer moves, the switch will be activated (connected to earth), and the warning light goes on. So you need to make sure the groove is centered before installing the switch. Refer to the wsm for a clear picture.

 

tou should not beed to bleed the brakes when you put back the switch.

Check if the switch is not leaking if the hole was previously closed/sealed by a bolt or similar, that could be the reason why the switch is not installed.

Waldi

Edited November 4, 2018 by Waldi

[AarhusTr6]

2 hours ago, Waldi said:

Rich,

the pdwa consists of a small plunjer sealed with O-rings. One side sees front brake pressure, the other side rear brake pressure. If there is a large difference in pressure (for example as a leakage in a wheel cylinder, caliper or hose), the plunjer moves to the low pressure side. The plunjer is normally “in the middle”, since the front an rear brake system use the same pressure, although the systems are separated.

In the center of the plunjer is a groove, in which the switch lever sits. As the plunjer moves, the switch will be activated (connected to earth), and the warning light goes on. So you need to make sure the groove is centered before installing the switch. Refer to the wsm for a clear picture.

 

tou should not beed to bleed the brakes when you put back the switch.

Check if the switch is not leaking if the hole was previously closed/sealed by a bolt or similar, that could be the reason why the switch is not installed.

Waldi

Thanks Waldi

The last bit I need is the connector which is out of stock, but think a spade connector across both pins works.

Rich

[foster461]

Any terminal that will fit on either or both pins will work. I was sure that wire should go to the oil pressure switch but looking at the wiring diagram for the 71 I see the brake warning lamp is also b/w for that year. If you ground it you should see a warning light on the dashboard.

 

Stan

[Chris59]

Be carefull, as explained by Waldi, if the "sensor" is no longer there, it certainly means that the "shuttle" is leaking : some shuttle are easy to rebuilt, as they are fitted with 2 o'rings (easily available), but the other model of shuttle, fitted with 2 small seals (very similar to brake or clutch  cylinder seals, but very small in diameter) seems to not be available.

So, you may need to find another pdwa unless you have access to a lathe : I'm on my way to make a small batch of shuttles in stainless steel, you may need to follow the same route.

 

 

 

[AarhusTr6]

25 minutes ago, Chris59 said:

Be carefull, as explained by Waldi, if the "sensor" is no longer there, it certainly means that the "shuttle" is leaking : some shuttle are easy to rebuilt, as they are fitted with 2 o'rings (easily available), but the other model of shuttle, fitted with 2 small seals (very similar to brake or clutch  cylinder seals, but very small in diameter) seems to not be available.

So, you may need to find another pdwa unless you have access to a lathe : I'm on my way to make a small batch of shuttles in stainless steel, you may need to follow the same route.

 

 

 

Thanks Chris and Waldi

Is there a quick and easy way to see if the shuttle is fitted or not?

Rich

 

[AarhusTr6]

45 minutes ago, foster461 said:

Any terminal that will fit on either or both pins will work. I was sure that wire should go to the oil pressure switch but looking at the wiring diagram for the 71 I see the brake warning lamp is also b/w for that year. If you ground it you should see a warning light on the dashboard.

 

Stan

Hi Stan, yes, I first had that idea too until checking wiring diagram where I can see its purple .  Wonder what happened to my anti-run`wire?

Rich

 

[foster461]

43 minutes ago, AarhusTr6 said:

Hi Stan, yes, I first had that idea too until checking wiring diagram where I can see its purple .  Wonder what happened to my anti-run`wire?

Rich

 

Rich, the anti-run on valve (mounted under the carbon canister) did not appear until 1973.

Stan

[Chris59]

1 hour ago, AarhusTr6 said:

Thanks Chris and Waldi

Is there a quick and easy way to see if the shuttle is fitted or not?

Rich

 

Remove the screw who replace the sensor, you will see if there is a shuttle in the pdwa (you should have one, or your car is seriously dangerous), but you need to take it out to know if it's the one who is fitted with o'rings or not.

[Waldi]

Rich, I installed new O- rings on my pdwa, think they came from Moss. Easy job.

If the shuttle is not installed, as Chris indicated, you no longer have a separated front and rear brake system. So worth to check.

Cheers,

Waldi

[AarhusTr6]

So like a rifle, open the breach and look inside... !   

Rich

[c.hydes]

Hi Chaps, just read through this topic, and am a bit worried about my `74 TR6 PI.

I don`t seem to have either the PDWA assembly/switch or a brake failure warning light. Having said that my car was a USA import and then rebuilt and converted to RHD, and then brought back to the `74 injection specification, so maybe the UK spec didn`t have them fitted. Can anyone shed any light and should I get one fitted? - Regards, Colin.

[brian -r]

I think that these items were not fitted to uk cars and as yours has been converted back from LHD possibly

UK spec parts were used.

Personally I would not worry about it or go to the expense of fitting them.

Just my opinion of course.

Cheers

Brian

 

[Waldi]

Colin,

I would not be concerned either, most classic cars to not have any brake failure warning indication; if you want to have an early warning of brake fluid loss, the float switch as used on modern cars provides a much better (and reliable) indication.

not sure if that would be an off the selve item.

Waldi

[c.hydes]

OK thanks Brian and Waldi, but does this mean that I don`t have a "dual braking" circuit ie a leak would lead to failure of the brakes on all 4 wheels?

 

Colin.

[stuart]

26 minutes ago, c.hydes said:

OK thanks Brian and Waldi, but does this mean that I don`t have a "dual braking" circuit ie a leak would lead to failure of the brakes on all 4 wheels?

 

Colin.

Not unless you had the PDWA unit fitted with no guts in it. I expect you have the normal separate circuit setup as per UK cars.

Stuart.

[c.hydes]

Hi Stuart thanks. I don`t have a PDWA assembly fitted at all as shown in the photo on Ed`s photo, just two copper pipes coming out of the master brake cylinder that go to "T-piece" copper connections. Sorry to be thick here, but does this mean I do have a dual braking system?

Colin. 

[stuart]

1 hour ago, c.hydes said:

Hi Stuart thanks. I don`t have a PDWA assembly fitted at all as shown in the photo on Ed`s photo, just two copper pipes coming out of the master brake cylinder that go to "T-piece" copper connections. Sorry to be thick here, but does this mean I do have a dual braking system?

Colin. 

Yes

Stuart.

[AarhusTr6]

Dear all

So went to summerhouse where car is stored and removed bolt from PDWA and looked inside to see if the shuttle thing was installed inside, but was shocked to see a small screw instead (see picture).  At this stage I thought 'phone a friend' before moving on..  I have tried uploading a picture but keep getting some -200 error - but the picture basically shows the inside from the top the PDWA with a small phillips screw jammed in.  No idea what Po was up to but have found a few surprises on this car...

Recommendations on next stage?

Rich

 

 

 

Edited November 18, 2018 by AarhusTr6