...now we remove C wire and replace with the new nest. A week later nest stop working...

Were you using the last Nest thermostat without a C wire? If so which model was it? I suspect the internal battery is not charging and has been depleted in one week.

When you did have the C wire, was it connected to the furnace control board C connection or another ground?

Do you also have an Rh connection? Do you have a voltmeter and can you measure the voltage between Rc and C, and also Rh and C?

I call another HVAC tech he come over do test find out if we jump RC and W write heat working fine so we replace another thermostat back to Nest again

So the weakest link is what? based on what you've done thus far?

Jumping RC and W is essentially what any "run" of the mill thermsostat will do to call for heat.

Did you call Google, the owner of the Nest? By and large the nest is mostly a sales gimmick. The warranty period is short, the trouble list with them is long... even if you get it to work with your system it won't be long until problems develop. These kinds of problems are often related to "heavy use" of your HVAC equipment.

If you live in a mild climate with little to no use, the nest may work for a time longer. Energy criminals that like to steal power from your HVAC, you can get away with it sometimes, other times you can not. (During heavy use as in running the equipment to heat or cool - it takes power to do that.)

I believe companies that offer the Nest are merely doing it to keep themselves busy with regular and often trouble calls. Before the nest, the thermostat could sit on the wall for 10 years or more with rarely a problem. Most companies are in this for $$. They want you to keep spending it, rather than offer you solutions that just work.

I service the Katy, Texas area.

@mike_home nest can take C wire but it can run without C wire. Before this problem, I was using nest without C wire for over 4 years until 3 months ago. Furness control board and everything grounded the HVAC guys test everything, we can't figure out why it runs for a week or two and blow out. This is why I come to the internet maybe someone experienced something similar.

Nest can take RC or RH not required to jump them 2. The test show I got 26.4V

@Austin Air Companie First I think I may get bad nest, then I go Echo Bee, but after 6 totals thermostats burn out it can't be them. It is my choice to choose nest my HVAC guys offer to put traditional thermostats since it works by just jumping W and RC wire.

So six thermostats have died so far? Sounds like a wiring issue caused by the first guy who came after the transformer episode.

Sounds like you need an electrician instead of an HVAC person.

@Austin Air Companie First I think I may get bad nest, then I go Echo Bee, but after 6 totals thermostats burn out it can't be them. It is my choice to choose nest my HVAC guys offer to put traditional thermostats since it works by just jumping W and RC wire.

Sure, you can choose whatever you want. You don't think I haven't had customer's who like to think they know better than me and want to pick something that could potentially damage their HVAC system? It doesn't matter to me... it's a guaranteed trouble call in the making. Maybe it's 6 months, 2 years, 3 years, 4 years? In this business we live for out of warranty trouble calls.

If someone offered to pay me money to install a nest and do it proper in terms of wiring and electrical requirements to minimize problems and they agree that the warranty of such product is limited to a small, small window of time (because of the nature of the nest). Then I would install it for them for money, not only the cost of the nest but labor and additional materials to do the job right.

BUT... due to the nature of the nest and how it operates it's not a matter of if it will fail, but when. In a high use climate (whether mostly cold or mostly hot doesn't matter) --- failures will come far quicker. Why? power stealing. You can't rob Peter to pay Paul. You can try, but the problems associated with such are well known at this point when it comes to the Nest.

So you had the nest before got it to last 4 years. The warranty ran out on that at two years (part only not labor). It should tell you something. If you want to ignore it, you can but that is not going to make it go away.

Just this last summer I replaced a nest to a traditional T-stat for a long time customer who has grown tired of repeated problems with his nest. Paying service calls for T-stat problems adds up. Cost of ownership is a thing.

If money is no object, sure go for it. Your choice, your money.

I service the Katy, Texas area.