Replaced wfco 8955 converter with power max pm4b-55-mba converter. I put the new PM in today and followed the testing directions. Step 1. With only shore power hooked up and all DC fuses pulled and battery disconnected (No load): voltage reads 14.74 on output side and no noise from converter. Directions say it should read 13.6 +/- .2Step 2. with fuses in and battery hooked up and shore power on: voltage reads 12.54 on output side and the converter starts humming. Nothing in rv is turned on. Voltage at batteries read 12.54. Directions say voltage should be the same or close. shut down all power at this time.Voltage at disconnected batteries read 12.48. first question is: the PM converter wires that hook to output side of fuse panel (DC side) are white and blue and both are 10 awg. I hooked blue wire to positive connector and white to negative. Is that correct? Not sure why at step 1 the voltage is reading 14.74 with zero load? And not sure why at step 2 the converter is humming with nothing on?I will be calling best converters in mourning. Any help, please.

Sounds normal to me. Although your battery does not seem to be getting any power. Did you check fuses?

Have you verified polarity to the battery?Open lead voltage sounds high, but that could be your meter. Do you have access to another meter to check?

AFAIK it should read 14.6ish when first turned on, then after 15 minutes it should drop to 13.6 unless the batteries need charging.If you have battery voltage at the converter "output" then the converter is not on at all (still getting the 120v input?) or there is an "open" in the path. Perhaps the new "lower portion" is not connected quite right the same way the old one was?The "noise" should be its fan, which is temperature triggered. It will come on more often when it is doing the 14.x voltage.

Since there is no color schedule of wires included with the installation instructions or the unit, we can't say if blue, white, green or pink are to be connected to which phase of the RV's distribution panel or battery.If you cant remember which wire is to be connected to which phase, testing for continuity to ground with those two wires would tell you the difference. One will have continuity, one will not.

Humming noise is not the fan. I can see the fan and it does not move. Humming sound is something else. Fan is free when I turn it by hand. The only difference in the lower portion of new and old is old has one red and one white wire for + and - to connect to output side, the new PM has one blue and one white wire. for checking polarity at batteries, are you talking about the converter supplying voltage/current to batteries to charge them. If so then no I have not.

new power max converter, problems | Good Sam Community

38 Replies

D_E_Bishop
Explorer
Oct 12, 2015
shane102, the unloaded circuit voltage is going to be higher than the loaded circuit voltage. Sounds normal to me.
shane102
Explorer
Oct 12, 2015
BFL13, why would it read 14.6ish when first turned on if the batteries are disconnected and no load of any kind.
enblethen
Nomad
Oct 12, 2015
Yes, at the batteries verify that the positive from the converter is going to the positive on the battery.
shane102
Explorer
Oct 12, 2015
Humming noise is not the fan. I can see the fan and it does not move. Humming sound is something else. Fan is free when I turn it by hand. The only difference in the lower portion of new and old is old has one red and one white wire for + and - to connect to output side, the new PM has one blue and one white wire.

for checking polarity at batteries, are you talking about the converter supplying voltage/current to batteries to charge them. If so then no I have not.
westend
Explorer
Oct 12, 2015
Since there is no color schedule of wires included with the installation instructions or the unit, we can't say if blue, white, green or pink are to be connected to which phase of the RV's distribution panel or battery.

If you cant remember which wire is to be connected to which phase, testing for continuity to ground with those two wires would tell you the difference. One will have continuity, one will not.
BFL13
Explorer II
Oct 12, 2015
AFAIK it should read 14.6ish when first turned on, then after 15 minutes it should drop to 13.6 unless the batteries need charging.

If you have battery voltage at the converter "output" then the converter is not on at all (still getting the 120v input?) or there is an "open" in the path. Perhaps the new "lower portion" is not connected quite right the same way the old one was?

The "noise" should be its fan, which is temperature triggered. It will come on more often when it is doing the 14.x voltage.
enblethen
Nomad
Oct 12, 2015
Have you verified polarity to the battery?
Open lead voltage sounds high, but that could be your meter. Do you have access to another meter to check?
time2roll
Nomad
Oct 12, 2015
Sounds normal to me. Although your battery does not seem to be getting any power. Did you check fuses?

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new power max converter, problems

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