If a cold water hose would blow out, would it look like a blue spark.

The water in the radiator must be hot. The hot water must flow through the heater hose to and through the heater core and back to the cooling system. Blockage in the hoses or an inoperative valve will prevent the heating. You might try loosening the return hose to verify that the water is flowing into the heater core and back out. Try this before everything gets too hot or disconnect the input and output hoses and blow compressed air through the system to be sure there are no obstructions. All switches and levers must be set to heat, and all valves open to permit hot water flow. Good luck. Hope this helps a little.

clair you may have a cold water problem, it may have filled with hot water and gone through wash cycle but as it got to rince it only fills with cold water ,the buzzing may be the cold water solenoid staying open and if there is no water passing through it will make a buzzing noise,
1.check the cold water valve # is on . it's what the blue /cold hose is connected to, also in some hoses there is a filter ,it's possible it could be blocked but unlikely.
2. check the cold water hose has not bend in half from the wall valve to the washing machine,this will stop the water flowing.
3. or it's possible you could have a faulty cold water solenoid valve.**
cold water pipe on wall> water valve# > blue cold water hose > * *cold water solenoid valve on machine.

Is this machine new? If not it is the controller, some of them use a temp sensor for the water mixing. Some of them can have bad connections at the control board.

When you released the cold end, it probably blew out some residue. Remove both hose from the engine and blow it out both ways with a water hose or air compressor. Add water each time, with air. Do this several times. I blow them into a box to see what comes out and when it stops coming out. This helps. Next would be replacing the heater core..All day job for me. I've done it. You have to remove the entire dash board and plenum.

Replace the thermostat.

You heater core is probably clogged up with contaminates! If the water is not flowing through the core for the fan to blow the heat off the core you will not get heat!

Possibly the heater core is 90% blocked. open enough to draw hot water in, (hose feels hot) but not enough volume to provide heat from very cold air, 10% hot water gets cold quick, coming from core..
Flush heater core in reverse direction - cold side in hot side out..

Just a theory..

Hi. Have your car aircon evaporator cleaned. Check also the drain hose. All water should go out of the car through the drain hose. There might be something clogging up the hose that is why water will run out the floor and that causes also the aircon to work intermittently.

Have a good one!

Makes a big difference. Cold water valve is is normally marked blue or simply cold water. connected to cold water tap. Hot water marked with red colour or simply hot and connected to hot water tap.(Red hose - Hot water. Blue hose- cold water.).

Thermostat may be sticking closed somewhat and overheating. What is a ----cold seal hose??