Brake Circuit Voltage drop RHD 92’ rev2 import

[Ryano085]

Hey guys I'm chasing a slight voltage drop from the Brake SW, i have 13.5V at the brake pedal switch but appear to only have 11.5V at the Green w/White trace brake light plug (and this voltage is common among each of bulb holder).

I have no voltage differential between Battery ground and White w/Black trace wire for ground (this is also common among each holder).

So I'm happy with the grounds, according to the schematic (which im not sure is the right one for my vehicle -3SGE & 3SFE Electrical Wiring Diagram found in this forum) there is a plug between the switch and bulb holder under the front dash on the left hand side call ID1, a 4-pin plug. for the live of me i cannot find it has anyone. has anyone had any dealings in this area.

Thanks everyone

[jimi]

What year is your car? UK or import ? Which diagrams are you using ?

[Ryano085]

My apologies, 92 rev 2 import. Following the 3SGe wiring diagram

[jimi]

Yes but which copy ? What's the pdf title ? One of them has a section that shows where all the plugs/relays/junction box's etc are located

[jimi]

IIRC, most of the plugs/connectors for the wiring to the rear of the car are not behind the dash, they are lower down in the passengers side footwell, there's a removable panel (same side as the door) behind it there's a junction box and a bunch of plugs/connectors.
I'll see if I can find the pdf that shows all the locations.
Even drawings for a later model will help as the locations are pretty much the same in all MK2's, wire colours and plug numbers may well be different but the locations are usually the same.

[jimi]

Try this one LINKY It's the 1991 Electrical diagrams, but should be OK for yours. Look at page 29 of the pdf (page 28 going by the diagram numbers)

[Ryano085]

Yes but which copy ? What's the pdf title ? One of them has a section that shows where all the plugs/relays/junction box's etc are located

im using the diagram from :Home/Know Your 2/MK2/MK2 General Info/Info:- BGB's/3S-GE & 3S-FE Electrical Wiring Diagrams im referencing P42 on the PDF.

[Ryano085]

Try this one LINKY It's the 1991 Electrical diagrams, but should be OK for yours. Look at page 29 of the pdf (page 28 going by the diagram numbers)

i have also been referncing the locations via that schematic. thanks for your help.

[jimi]

Have you found the connector?
The wiring definitely runs up the passengers side the through to the engine bay. I traced the G/W brake light wire when I was helping Portgordon fit a high level brake light, theres some (poor) pics here https://mr2oc.co.uk/know-your-2/mk2/mk2 ... moval.html

[Ryano085]

Just to update, I may have been chasing ghosts, my PSU powering the loom was set to 13.5V but my meter read it as 13V. I measured the Voltage at the fuse holder at about 12.5V and measured again at the plug going to the rear brake loom showing 12V. I finally measured the bulb holders at just over 11.7V.

It’s not ideal but I guess old wiring (well in my case) just naturally has a bit more voltage drop then one might expect.

[jimi]

What was the rating of the PSU ? i.e. output current ? Is it a regulated PSU ? If it's low output then with a load on it may well be just voltage drop your seeing.
What does your meter read if measure the output with nothing connected to it (i.e. no load)