Replace idiot lights with LED - No work

So I'm working on replacing the stock instrument cluster in my car with all Autometer gauges and LED idiot lights.

So going from this

To this

I've got all the gauges working but the oil pressure, brake light and alternator lights do not work.

These are the lights that I bought and I am wondering if I need to put in a resistor inline?

https://smile.amazon.com/gp/product/B071YTXV4R/ref=ppx_yo_dt_b_asin_title_o07_s00?ie=UTF8&psc=1

Any thoughts?

In reply to GPz11 (Forum Supporter) :

I assume you have checked the polarity of the diodes?

Try hooking one straight to 12v like a battery and see if it works. You also might have them hooked up backwards, LEDs are sensitive to polarity, incandescent bulbs are not.

Some gauge lights work in 'reverse', ala the alternator light. Power comes from the cluster, to the light, then to the alt field wire. If the alt is working, it will supply 12v to the field wire, and therefore you've got 12V on both side of the alt light and the light is out. In many cases you also need this voltage into the field wire for the alt to work at all. 

The oil pressure and brake may be similar where you've got "power" at the dash and the light comes on when the sensor goes to ground, rather than the lights being grounded at the dash and coming on when the sensor goes to 12V. 

If that makes any sense at all. 

I've plugged them direct to a battery and they do light up.

I'll try to reverse the polarity and see if that works.

I don't think that you are going to get a LED in place of an incandescent lamp to work for the charging lamp.

Unless you rewire.

"If the alt is working, it will supply 12v to the field wire, and therefore you've got 12V on both side of the alt light and the light is out."

Yep, that's how many alt WLs worked back in the day. Sounds like it wouldn't work, but that is exactly how they were wired for many years (US stuff anyway).

Meanwhile GPz, if worse comes to worse, you may want to look into specialty replacement warning light LEDs that are made for your specific application.

noddaz said:

I don't think that you are going to get a LED in place of an incandescent lamp to work for the charging lamp.

Unless you rewire.

I have an LED in my Torino.  It was plug-and-play and works fine.  However, at idle it flickers on and off due to the way LEDs work and isn't noticable with an incandescent due to they way they work.

Ok, I was comparing the set up on the original cluster vs how we wired up the new one.

We wired up the grounds together when we needed the powers together and the ground controls the circuits

So we’ve got some rewiring to do.

As others have said you need to check to see if the check engine light  or warning lights come on by grounding at the sensor / ecu or not.  NA8 based Locost 7, I used an LED as a check engine light / warning light etc.  To get it to operate normally, I had to utilize an relay.  The ECU and oil pressure switch were wired in line with the ground wire of the relay.  constant 12 v to the relay and the LED on the load side of the relay.  Once the ECU or the oil pressure switch ground the the relay closes allowing the LED to come on.  Before I did this, I had issues of LED partially coming on and flickering when it shouldn't.  Not the same issue you are seeing, but something to consider.  If you have both switches that are NO and NC going to the same LED, you can wire two different relays in parrallel to the LED.

I have used a LED for my alternator (vw) as well as a few warning lights, they work just fine. As said before, polarity matters so use your wiring diagrams to figure that out.

Got to play a bit today on it. Haven't fired it up yet but at least the lights come on like they should with the key on.

The brake light is on but is dim for some reason.