Dash warning lights / trip meter reset

Hi all!

First a quick thank you to everyone for you help so far, I would be even further behind schedule without it!

Second: I’m replacing the dashboard on my '71 +2S 130 but have bought a dash off a later model which only has holes for 3 warning lights. I understand fron the wise seers on this forum that the lights for the brake failure and handbrake were combined in these models and was wondering if anyone knew how I might go about re-wiring to make this work?

Also a picture of the later dash in-situ would help for when I label up the new dash.

(I realise this is a form of blasphemy but I really don’t have any choice at this point, I can’t afford another dash and need to have the car put together and sold within the next 6 weeks!)

I’m also curious about the trip meter reset button - is this really just mounted randomly under the dash?! If so could someone send me a picture of this as well?

My eternal gratitude as always!

Tim

(I had posted this in the +2 section but not had any advice so I’m opening it up!)

(p.s. - if anyone is interested in a good condition +2S 130 with an excitingly rare cam cover please let me know!)

Tim:
I will try to help, but please note that due to the varieties of Plus 2 wiring that are in my book, I can’t be too specific to your car as not sure which variant you have. For reference, my car originally followed the Federal diagram, but I expect yours may be different if in UK. For reference, Federal diagram is labeled March 68 to March 69 in my book. Note just using this to explain the circuits; yours may be different.

Brake warning light in mine is actuated by the PDWV or “Pressure Differential Warning Valve”, a hydraulic valve plumbed to the dual circuit master cylinder which indicates failure of one of the dual brake hydraulic circuits. Your brake fail warning light, if in a single circuit brake system, may be triggered by a low brake fluid warning light connected to the cap of the single circuit master cylinder?

So, confirm first how your brake warning light is triggered.

In the diagrams I examined, the separate brake warning light and the hand brake warning light are triggered in a different manner, and must be changed to consistent electrical configuration prior to combining them.

The Handbrake switch is powered by a green “hot in run, fused”, and the warning light is grounded at the bulb holder with a black. The switch and warning lamp are connected with Green/Purple. So, the current flows through the switch first, then to the dash lamp, and to a ground located on the warning lamp holder.

The brake fail warning lamp is the opposite. The lamp is powered in the original wiring in my car by a Purple?Hot always, fused?. The PDWV or, I am assuming, the low fluid switch, is grounded when closed. The lamp and switch are connected by Brown-Purple. So, the current flows through the lamp first, then to the switch, and to a ground located on the switch.

So, second, confirm where your grounds in the two circuits are located; they will consistently be black even if the other colours vary in your particular car. Easy way is note if you have a black at the existing warning lamp or not, as you have dash out.

Third is to change the wiring such that both switches go to ground. This is the easiest way to make the switching consistent as you have available power at the dash area, and it is easy and safe to run an additional ground as required to the handbrake switch. In the dash, I wired both my handbrake and brake fail lamps to be powered by Green Hot in Run, Fused, as this way if the brake fail is triggered, the warning bulb will be extinguished when the key is shut off. In your case, it is just a green power wire to the single bulb holder.

It is essential that the single warning lamp is powered by Green, “Hot in Run, Fused” or White, “Hot in Run , Unfused” or else your handbrake warning will be on when the car is parked and drain the battery! I am betting this set-up did not meet the letter of the law in the US as the brake fail is available only when the car is switched on, hence the weird wiring variations.

Both connecting wires to the switches are now connected to the single warning light. This essentially creates a parallel switch circuit to the single warning lamp, so if either the handbrake is on, the brakes fail, or both happen at the same time, the warning bulb will light. The diagram I looked at for the single lamp set-up uses Black-White for wires from the lamp to the switches, but I would just use the existing wiring in your car now.

One further detail. My car has a simple push button switch, almost as an afterthought, located on the driver?s side panel below the dash and above the tunnel area. This switch is provided to test the brake fail warning lamp. It simply grounds the warning lamp, lighting it up. I do not see this in the single bulb circuit, and I don`t know if you have this feature on your car; I doubt it though. I guess it was required by US law. Anyway, I would not bother adding this feature in a single bulb set-up, as you simply pull on the handbrake to test the bulb.

HTH. Sorry for length and lack of specifics, but hopefully explanation will assist in figuring out the details.

Tim:

Not sure if you got the brake warning light sorted?

Anyway, for your second question regarding the odometer reset, I was looking over my dash today (it is out of the car right now). The odometer reset cable on mine mounts to the drivers side bracket that stabilizes the dash and also holds the door switch for the courtesy lights. The reset cable stem should emerge below the dash surround (crash pad) on the far outside where the dash mounts above the door opening. The cable is held in place with a chrome notched nut similar in shape to the ring around the ignition key, but I think any appropriate nut would work fine.

Glad you asked as I might have forgotten to install when I put the dash back in!

Note again mine is the type with four small gauges and the flat safety switches (not a Plus 2S), so your’s may be different.

HTH

Many thanks Stu!

I don’t suppose you have any pictures that would help with the trip reset?

Here is a couple of pics. Sorry for dreadful pic quality; just trying to sort out my phone camera, file formats for the list, and resolution issues when I post.

Cheers


That’s perfect, thanks again!

Love the wiring by the way, is that a new loom?

Glad the photo works. As I said, yours may be a bit different as the S model seems to have additional switches under the dash?

Yes, the wiring is all new. Due to all the wiring differences in the models, I decided to use a Premier Uni-Loom from Spyder. It worked out pretty well as I was able to easily modify it as required; it comes held together with twist ties. I also was able to add relays for all the accessories pretty easily, and use all modern connectors. Hope it all works when installed, but checks out on the bench OK.

Cheers!

Stu - double check the (old) switches. My dash is all installed now; but the LH window switch - il ne marche pas.

Keith

Thanks Keith, I will double check them prior to installing. I added four relays for the windows to lower the load on the switches and hopefully keep them working.

Cheers!

Hi Stu

Think U have all the info you need but have attached some pics 4 U as well. When I rebuilt my dash I took a number of pictures before I stripped it down. I have attached the two small plates that I called “bracket anchors” (don’t know if they have a official name just what I called them).

As u will realise us Brits drive on the wrong side of the road ! but I think the pictures should convey the idea OK.
when I put the two door switches back I fitted a small metal plate to link them and provide a sure earth between them rather than use a large tag.

Hope this helps best of luck

Bob