Nest 3rd gen learning Thermostat

[ConnorMcG]

Hi I've installed this thermostat, heating works using the USB cable, I have 11.94v coming out the t1 and t2 and at the base but when it's attached coming up with no power to the thermostat, cable is fine as there is 11.94v at the cable end, can anyone help me if it's a problem with the base or thermostat which are brand new, already had a faulty heatlink which I had to replace, I've tried reseting the hest link and thermostat, cant be a network problem as its working on the USB cable

thank you

[Frustratedddd]

This will be nothing with  your Network or reset, sounds like a component issue.

From the details you state I would say a faulty Base.

You say the base is brand new, where did you purchase, and did you purchase as ''Brand New''?

[Worzie]

Do you have a C wire connected?

[Frustratedddd]

Not in the UK he wouldn't!

Not your fault, as yet another issue on this forum where we don't know where the user comes from.

Come on Google, I have been asking for 4 years about this problem, get it sorted for heavens sake.

Make a section for USA and one for Europe. How hard would that be?

[ConnorMcG]

iam from UK so no we don't use c wire just 1.5 4 core at thermostat, they out the motorised vales under the bathtub...  but yeah it was from eBay but was brand new, having to replace the heat link I was never actually able to test the base, so it went over the 30day period so again I got to buy another thing, costing so much just ridiculous gotta be at the pin end that's the problem, can take apart and test try and fix myself but I think it's a joke I have to do this buying a brand new product 

[Frustratedddd]

OK, if purchased from ebay and saying Brand New there may be an issue!

You are getting 11.94v at the terminals at the base plate from the Heat Link you say, and that's correct.

That means the output from the T1 & T2 terminals at the Heat Link are correct, and getting to the base plate. That’s good.

I assume you can also see a usb voltage in the Tech screen on the stat, if connected by usb something like 3.6v?

This is what I would do to start with, remove the 4 screws at the rear of the base plate, and have a look to see if anything is blown. Look very close at the back of the PCB board to see if any components are blown. The usual one is top right as seen in the picture. Look close at the white plate and see if any blown marks on that, obviously if totally blown that will be easy to see.

Would you be OK with that? Got to start somewhere!

[ConnorMcG]

Hi yeah I've getting iver 3v on the use side, gotta be connection to the pin side, but yeah I will open it up and have a look, I am an Electrician by trade, I don't have a soldering kit for that size pcb, suppose I will invest in one as I need to fix the old heat link that the diode is blown in, I will send a photo once I get home 

[Frustratedddd]

Depends if damaged, I’m just starting at an easy option. 

Can’t image any damage if sold as brand new, but eBay, well who knows! 

[ConnorMcG]

I Have sorted the base out its now able to be powered wired up but the base is overheating now and inside the wall behind the thermostat is hot, getting sick of this product, the cable is suffient to handle 12v dc...

[Frustratedddd · Accepted solution]

What exactly was wrong with the base plate?

[ConnorMcG]

had no voltage going to the pin which connects to the thermostat

[Frustratedddd]

Why did that happen? Faulty part, damaged etc.?