Newish Surflo pump problem - Battery Drain

[ianrjam]

When my pump switch is on but the pressure is up, the pump switches off until some water is used - OK so far. But if it is left on it drains battery power. When the pump is switched off, the lights get brighter and the battery recharges. I thought that when the pressure switch stopped the pump, no more 12v electricity would be used. Running down the battery has been bothering me for years. I've gradually checked/replaced parts and have now narrowed the problem down to this. Where is my electricity going?
78 Tradewind

[Inland RV Center, In]

Originally Posted by ianrjam

The battery discharging in my 78 Tradewind has been bothering me for years. I've gradually checked/replaced parts and have now narrowed the problem down to this. When my pump switch is on but the pressure is up, the pump switches off until some water is used - OK so far. But if it is left on it drains battery power. When I switch the pump off, the lights get brighter and the battery recharges. I thought that when the pressure switch stopped the pump, no more 12v electricity would be used. Where is my electricity going?

You could have some corrosion on the water pump pressure switch terminals, that you cannot see. Even so, the current drain could not be very high.

As a suggestion, place an "ammeter" in the battery line.

See what the static current drain is.

Then disconnect the 12 volt wire from the water pump pressure switch, and check the ammeter.

If there is no change, then your only problem, is you will have to keep on looking. You can use the same process, by disconnecting one fuse at a time in the Univolt. That would at least tell you what circuit is causing the battery drain.

Andy

[azflycaster]

When my pump switch is on (all day when camping) the switch on the control panel is on. It should be a very low draw, bit is your switch an original? This could be another place to look...

[RickDavis]

Normal pump operation is for the pump to shut off and not draw any power until it runs again. Mine stays turned on for months on end.
I think you need to measure the current flow in the lines under question and then start disconnecting stuff until the drain goes away.
These can be tough to find

[DKB_SATX]

Take this with a grain of salt because I don't have experience with the particular pump in question, it's pure theory... but if the pressure-cutoff switch has failed or has just ended up with a higher pressure point for operation than the pump can produce, and it's a positive-displacement pump, wouldn't the pump stop when it built up the maximum pressure it could attain, with the motor pushing against the pump until the pressure dropped and it could start pumping again?

It seems that this would kill the motor in fairly short order, and would also cause a power drain whenever the pump is switched on, whether or not it's able to actually pump water.

[ianrjam]

Thanks everybody. Sorry to take so long to get back on this but I don't see the Airstream over Winter and so work resumed in Spring. The problem seems to have been our old friend the Univolt. We took down the central ceiling panel and checked out all the wiring circuits for possible shorts, wetness, etc. and rewired the old system TV aerial (antenna). Once we were sure everything was OK, we disconnected the Univolt and the battery held its charge on the next trip. We have a British 240V to 12V equivalent unit with charger which cost about $110. Everything seems OK but the battery has probably suffered from the discharging and is unlikely to be as good as new. It's 4 yrs old.

The Tradewind has only one battery and the tow vehicle charge line seems to go to a second battery position in the fuse box. All the diagrams I've looked at seem to vary and show two batteries. Would it be better to reconnect it to the position my single battery is wired to? I don't seem to get a full charge when running with the fridge on 12V. That would mean taking the white wire below charge terminal 15 on the attached diagram to the position below the fuse on position 11 (moving it from 12). The Univolt connections at 18, 19 and 20 have been removed and there is nothing connected to terminals 12 and 14.