New replacement in-line heater (C3B54P0-3002AU0) inop.

if oy purchase new unit of same capacity it will come precharged. You do realize that you may have to replace A coils in air handler. How do you intend to vacuum lines and hold vacuum for 4 hours.. If you are talking window unit toss it and buy a new one.

There are many factors in these mini splits.
Was it working previously?
If it is a new install it could be a long line set, low on refrigerant
While in heating go outside and feel the bigger of the two coper lines that should be warm to the touch.
Force it into cooling and a good P.S.I.G. is 125 on the service port.
Last, did tke line set get kinked?
So if in cool you have 125 psig. In heat you have a warm line on the fat coper line at the outsid unit, no kinks and a short line set, Time to call a service technician out.

The heater core is warmed up by the engine coolant. Usually there are two main coolant lines from the radiator to the engine and return from the engine to the radiator. Also there are two other coolant lines that supply warm coolant to the heater core and return it to the water from the engine.. So yes it could be that your car needs a new coolant line or both if the existing ones are bent or plugged(this is rare. But possible).
You can visually inspect the plastic hoses that supply the heater core to see is they are bent. And if possible when the car is fully warmed up and the heater is on at max heating capacity. You can touch both hoses that go into the firewall to check if they are both hot. (Very hot. But bearable) if only one is hot. That means there is an obstruction (hose would be plugged or heater core itself could be plugged). If both hoses are hot. Then the issue could be at the vent diverters behind the dash.

could have air lock or heater core plugging up. heater cores should be back flushed.when car is hot touch one heater hose at a time both should be fairly hot if both hot then the problem is temp control.

Shut off power, Shut off water. Disconnect electrical and water connections. Drain and remove broken water heater. Put new water heater in, and reconnect water (usually with new flex lines and shut off valve), install and reconnect new safety valve, reconnect electrical. Fill and test for leaks, (release air and first batch of dirty water through bath tub spout so you don't plug faucets) if all is ok, turn on power, wait, take warm shower!

Btw, I’m available to help over the phone in case u need at https://www.6ya.com/expert/perry_14036f9bc71cde6a

an inline heater does not heat the water it only maintains the water temperature that is in the bath. try filling the bath with the required water temperature and see if the heater maintains that temperature. good luck

Try taking apart your Heater Core (old cars are attached to the firewall, new cars have thiers under the dashboard) and check for any mouse nests, inoperative door openers (openers usually run off of vaccume or small electric motor), obstructions of any kind, etc. most of the times these problems are resolved with something simple like a pen having fallen in and blocking the doors from opening. also, have your A/C checked to see if its full or leaking by a professional (unless you know how to do it yourself) your heater core could also be clogged so let the engine warm up and turn on the heat( yes i know it wont work) but if the core (looks like a small radiator) is cooler than the coolant temperature then it should be replaced. while your digging around down there it would probably be a good idea to check out your squirrell cage (blower motor for the heater core) and see if it spins when the power is turned on.
         Hope This Helps!
                                 Joe.

First thing I'd do is make sure your coolant level at radiator is up to proper level.Your auxiliary heat/cool unit should be in behind the right rear interior panel . (passenger side) If you remove that panel & check the hoses or lines going into it, they should be warm/hot to touch when heat on & engine warmed up to operating temperature. If not, it's most likely a problem with the electronic control, not allowing coolant flow to it, and I'm almost sure that the control cannot be fixed, but needs to be replaced. Triple check all your fuses for heater controls etc, but if everything else is working except the heat part, I'm guessing control at dash needs replacement.

sounds like the rheostat (aka rotary swithch) is opened (fried). can get new one on www.appliancefactoryparts.com for 8.19 + s/h. need to know how to solder though. otherwise you will be looking at having to buy new unit for $120+