Need electrical help QUICK-- Luft air pump rheostat malfunction

[redfishsc]

I have a Luft pump that drives my DIY skimmer, and the other day I accidentally knocked over my collection jug that holds skimmate.

The luft sucked some of the skimmate up into it's housing. Maybe a tablespoon or 3.


I immediately unplugged it and rinsed it with denatured alcohol, flushing it out well.



It worked fine for a couple days, and now the rheostat is shot. It started out working fine, but if you backed it off to anything lower than 10, the pump would stop (the diaphram would still quiver, but not enough to produce air).


Well now the thing won't run at all- the rheostat won't adjust. I'm 100% sure it's the rheostat.



I always run this thing wide open anyhow, is there any way I could just splice the white wire (coming from the power source/outlet) to the blue wire (going from the rheostat to the motor coil)??

Would this run it at normal "wide open" or would it be overload?


Any help is much, much appreciated! I need to get something running on this skimmer SOON!

 

[redfishsc]

Anybody!?

 

[Mike31154]

Without a diagram or photo it's kind of risky to offer any advice here, but if you're that sure that the rheostat is finished, then you can try a shorting wire between/across the rheostat terminals. That should effectively take the rheostat out of the circuit. Should be able to do this without cutting or splicing any wires. Goes without saying that everything should be unplugged. A short piece of wire the appropriate size should do the trick.

Then off to an electronics supplier to source a new rheostat.

 

[redfishsc]

I spoke to Coralife on the phone, and they agreed to replace the pump for me (how cool is that!).

Unfortunatley it's out of stock for the next couple of weeks.


How would I know what kind of rheostat to get?


Also, if I jump the wires together, and it works when powered up, how would I know that everything is a-OK? Perhaps check the amperage going through it compared to the spec amps it should run at... right?

 

[Mike31154]

To replace the rheostat you'll need to know the value of the component. Only way to do that is by part number or by measuring the rheostat's total resistance. Likely not possible on such an inexpensive (I think) component, especially since it's already fried. Depending on the position of the rheostat control knob, it will add or remove resistance in the circuit to the pump motor/vibrator. When it's all the way down it is in effect a dead short, so the same idea as if you jumper the rheostat terminals together. If it works when powered up you should be able to tell from past experience regarding its air output. You say you always run it wide open, so jumpering the terminals will be just the same, since you've taken all the resistance out of the circuit by bypassing the rheostat.

How many terminals are on the rheostat, two or three and if three, are they all populated with a wire? It it's only two wires, you can cut them off and splice them together, that would be the same as jumpering across the two terminals. Either way, you're eliminating the faulty rheostat from the circuit allowing full voltage potential to be present at the motor/vibrator.

 

[redfishsc]

Mike, there are only two wires. The white wire that leads in from the plug goes into the rheo, and the blue wire goes from the rheo to the motor coils.


Could the jumpered version possibly going to send a higher voltage or amperage through the coils than the rheostat did at wide open?


sorry that I'm not all that electrically inclined. I know how to splice a wire and use a wire nut... and that getting shocked hurts quite nicely... but that's about it

 

[Mike31154]

<a href=showthread.php?s=&postid=15645648#post15645648 target=_blank>Originally posted</a> by redfishsc

Could the jumpered version possibly going to send a higher voltage or amperage through the coils than the rheostat did at wide open?

No, when the rheostat is turned fully down it should offer 0 resistance, which is the same as shorting the wires together, should be no problem. So you can do the wire splicing that you described in the first post. The coils in the pump will be rated to handle 120VAC from your home outlet.

 

[redfishsc]

Great!

I'll fiddle with this today at the shop. I appreciate the help!

Matt