Mr Sandman wrote:



Mr Sandman wrote:


I have an aircon unit that failed. Fault code 'PU' says the capacitor
charging circuit failed, this is confirmed by checking the voltage at the
three large electrolytic caps which show 43vdc, but oddly 85v ac. The
expected voltage at the capacitors should be 180-380vac.


** Gobbledgook.

Large electros acquire *DC voltage* after being charged.

What sort of multimeter / voltmeter are you using ??

An old moving coil one by any chance - many of the latter read double
voltage on the AC ranges compared to the DC ranges if mistakenly used for
DC.

Reverse the probes and the reading drops to zero.

---------

I am using a digital multimeter, a fairly decent one.


** Make and model - please !

Probing the caps
directly i get the voltages i mentioned.


** What about when you reverse the leads?

FYI:

There has got to be at least one DMM maker who uses a half wave rectifier directly coupled to the DC meter circuit - mimicking how an moving coil multi-meter does the same job.



.... Phil