old hitachis

[dannycool]

i am currently re-commissioning some old Hitachi cassettes unfortunately i don't have model numbers because the nameplates are faded,all i can make out is UZU-Q on the outdoors and the the date of manufacture is 1998.

So my problem is that they seem to be running permanently in heating, so i traced the problem back to the indoor board sending a 240v signal down number 2 on the interconnecting (which energises the 4 way valve solenoid) even when i switch the controller to cooling. Now we have fitted replacement controllers (the old slide type) and the exact same thing is happening on two systems.

My conclusion is that the pcb mounted relays are sticking, but is it more that a coincidence that it does this on two systems? As you can imagine i am hestitent about ordering two new boards until i am 100% about it .

I have little experience with hitachis and even less of ones this age, so am i missing something out or not doing something i should be.

Thanks in advance

Danny

[rude]

could it be a sensor thats telling them to run heating?

[superswill]

is the 4 way valve/coil working on change over? is the compressor contactor "stuck in"? are the interconecting cables crossed? (i had this a while age)

no answers really just a few ideas

[nike123]

You should check if low voltage (control) is present at coil of relay. If it is not, then relay is welded . If yes, than you have some control problem.