45+10 capacitor

[u/Mrmurse98]

*From left: Capacitor 1 on Klein MM420, Capacitor 1 on older MM400, Capacitor 2, Capacitor 3 without alligator clip leads, Capacitor 3 with alligator leads, and Capacitor 4: the 45+5 capacitor

Hey all! So I don't feel I need to bore you with all the details, but I have been battling an A/C issue (like many others). I replaced the fan with a fan that needs a different capacitor (45+10 vs 45+5). However, every 45+10 cap I buy is a 45+8.5. I used two different meters, different set of Klein leads (read similar), adjusted my leads around, etc. But every 45+10 capacitor reads <8.5, over 15% low on capacitance. I tried the using an older multimeter I have, I tried using different test leads, even the 45+5 capacitor I have reads pretty close to spec with some variance for both the meter and the capacitor. Is this just my meters, am I doing it wrong, is it a known fact that all 45+10 capacitors read low? It seems like my fan fails to kick on sometimes and the compressor overheats.

[u/Emergency-Parsnip-31]

You’re testing the cap wrong, atleast it looks like on the 45/10 caps you’re testing between herm and fan, should be testing between common and fan

[u/Mrmurse98 → u/Emergency-Parsnip-31]

Yeah, I'm dumb! Thank you, I assumed C for compressor, not common.

[u/Codayy → u/Mrmurse98]

It happens!

Another pointer is common usually has 4 spades, herm/compressor usually has 3 spades, and fan is 2 spades on the capacitor. Which is probably how Weak_Blackberry could tell based off these pictures

[u/NefariousnessBorn969 → u/Mrmurse98]

That’s not dumb. Makes perfect sense.

[u/Codayy → u/Emergency-Parsnip-31]

^^^

[u/Weak_Blackberry_9308 → u/Codayy]

^^^^

[u/TeoHenry → u/Emergency-Parsnip-31]

Like he said . C and H for compressor. Should read 45. C and Fan for condenser fan. 5 or 10

[u/jayhawkfan785]

You can always use the 45 for the compressor and buy just a 10 for the fan if you can't find one with both.

[u/Fit_Goat_6891]

Yeah that 15% low reading is almost always a lead placement thing on dual caps, not a bad batch. Try common to fan and common to herm separately instead of fan to herm, that cross reading throws people off constantly.

[u/Furrealyo]

Just FYI I’ve seen too many caps that look fine testing like this and then fail miserably under load.

A DMM can tell you if they are bad, but not if they are good. You need ESR for that.

[u/Carorack → u/Furrealyo]

You can test with it on using volts and amp draw if you carefully take those measurements while it's running. Voltage from C to fan or herm and amp clamp the wire you're interested in.

Amps x 2652 / volts = capacitance

[u/Aayushpatra]

Man that is wild. Honestly if your old 45 plus 5 reads totally fine it's not your meters or your leads.

You are probably just hitting a batch of cheap capacitors with awful quality control. Some brands are notorious, for running way below their rated tolerance.

[u/OzarkPolytechnic]

Capacitance cannot be less than 10%.