OMC #175000 VRO Tank Float Switch Question

[Chaparralbob]

I have a 1990 70HP Evinrude. I purchased a replacement oil tank with float sensor.

With the tank completely empty (dry - still new), I get no warning beep. I ground the tan wire leading to the tank, and the buzzer works fine.

Is this sensor just a mechanical switch, or does it have electronics in it? If it has electronics in it, are the connections polarized?

I have read that some of these tanks are mechanical switches, and some have electronics. What I haven't found is what the 1990 70HP has.

Thanks,

Chaparralbob

 

[d.boat]

Re: OMC #175000 VRO Tank Float Switch Question

I have a 1990 70HP Evinrude. I purchased a replacement oil tank with float sensor.

With the tank completely empty (dry - still new), I get no warning beep. I ground the tan wire leading to the tank, and the buzzer works fine.

Is this sensor just a mechanical switch, or does it have electronics in it? If it has electronics in it, are the connections polarized?

I have read that some of these tanks are mechanical switches, and some have electronics. What I haven't found is what the 1990 70HP has.

Thanks,

Chaparralbob

I don't know if this will be of any help at all to you, but... are you sure you have the right tank/sender (1995 and earlier) for your warning system? I believe the electronics in the 1996 and later are different because of the System Check gauges.

Although the wires on the current edition of the pre-96 tanks are color coded tan and black I don't believe they're polarized. The reason I say that is that my original tank (from 1990) had a simple two strand black cord, not unlike lamp cord in appearance, not color coded. One black strand was connected by butt connector to the tan wire at the engine, the other directly to ground. My "new" tank has color coded wires, and although I connected tan to tan and black to ground, I don't believe it mattered because of the way the older one was.

If you're sure you have the right tank, as I recall, testing the sender is just what you did - hook it up, turn key on, and the alarm should sound intermittently every 20-40 seconds if the float is low enough. I can't remember if there's an actual multimeter type of test in the manual, but I would guess it's just an "open / closed" sort of thing tested with an ohm meter or 12 V DC.

 

[Chaparralbob]

Re: OMC #175000 VRO Tank Float Switch Question

Apparently the 1990 version of the tank sender has electronics in it. There is no direct connection to one of the little rails that the float rides on. The other rail is connected to what must be the ground lead.

Here goes....

When I connect the tank sensor, with the tank empty, I correctly got a beep every 20 or 30 seconds. I filled the tank, and the pulsing went away. But, I get a very low volume whine from the buzzer (piezo) whenever the tank is connected. The buzzer I have is off of an older V6 Johnson that a friend of mine had scrapped out. Without the tank sensor connected, shorting any of the tan wires to ground sounds the buzzer and the buzzer is quiet when the tan leads are not shorted to ground.

I put a voltmeter on the tan wire. Without the tank sensor connected, the tan wire is a close match to the battery voltage. With the tank sensor connected, the tan wire voltage drops to about 10 volts. This would make sense, as the tank sensor electronics must draw some kind of current.

Question is, what is the normal voltage on the tan wire to trigger an alarm? Since most all of the other sensors short the tan wire to ground, it seems like a 2 volt drop from the battery voltage shouldn't start up the buzzer.

Thanks for any help with this!

Chaparralbob

 

[d.boat]

Re: OMC #175000 VRO Tank Float Switch Question

I thought you weren't getting any alarm when the tank was empty .... did you change something? Because now it seems like it's working fine except for the low level buzzing you're hearing.

Did it not do that with the old tank that you replaced?

I don't know about the low level buzzing you're hearing. I'm surprised the tank sensor draws any current when it isn't "triggered", but I've never tested mine. Without claiming any real expertise, I'm thinking "low level voltage leak.... low level buzzer...hmmm) I wonder - do you have the old tank to compare this to? Maybe there's a defect.

 

[Chaparralbob]

Re: OMC #175000 VRO Tank Float Switch Question

Turns out that the tank sensor is polarized. When I reversed the wires, the sensor started working. Thank god some engineer put reverse polarity protection in it! I had cut of the some of the 12 feet of wire that came with it to shorten it. I assumed that it was just a mechanical switch, and not polarized (polarity sensitive). The factory end of the wire had a ring terminal on one lead that the instructions called out as ground (should have read them better!).

I measured a couple of things to figure out what is going on with the low level tone that the tank sensor causes. I measured the current draw of the tank sensor - it is very small - .0008 Amps or 0.8 milliamps. Apparently, this is enough current to sound the piezo buzzer at a low volume. This is not out of line with some of the ratings given for Radio Shack piezo buzzers. The original buzzer must require a much higher current to activate.

I think I have a scheme for fixing this - I'll let you know how it works out.

Thanks very much for your help with this!

Chaparralbob

 

[d.boat]

Re: OMC #175000 VRO Tank Float Switch Question

Interesting about the polarity. Like I said, my original tank had undistinguished wiring, but the replacement had tan and black like yours (so of course I wired them to tan and black!). I ASSUMED that the original wasn't because both strands of wire were black, but now that I think of it, one strand did have what looked like a factory ring connector for the ground... so it probably did have polarity. The "new" one (not new, just newer), was obvious becase it was color coded, tan to tan, black to ground.

Anyway, moot point since you figured that out, but I'm glad you clarified my erroneous ASSUMPTION.

I'll be interested in hearing your findings. If I have time and inclination I might see if my tank is drawing any current like yours. I still wonder if the current leak is a defect, or if it's the "old" buzzer you're using.

As for the buzzer, when you say you got an older buzzer - how old? the reason I ask is that my control box (where the buzzer is located) is from at least a 1982 engine (my previous engine).

My understanding was that any engine that uses the "big round red plug" is compatible with any control box that has the corresponding plug, no matter how old or new..... and that would lead me to think the alarm buzzers are all compatible too. The buzzer is sounded from the same wire coming through the main wiring harness from the Big Round Red Plug to the control box, no matter what the source (overheat, fuel restriction, no oil, low oil). The only difference among the different alarms being the intermittent or constant signal sent through that wire by the various sensors??

Did you actually transplant a buzzer from the old control box into yours, or was it the whole control box (with the Big Round Red Plug).

 

[Chaparralbob]

Re: OMC #175000 VRO Tank Float Switch Question

I don't think your assumption was wrong - I have read about some older tanks that had only a simple mechanical switch. It was my mistake to assume that they were all that way.

I got the buzzer as a single item, out of the control box. The old pontoon I have uses what they call a "concealed side mount" remote control, but the engine does use the "red plug" connector.

I really don't know anything about the V6 electrical system, but I'll be doing some research after I find the year of the engine the buzzer came from.

It does make sense for the tank sensor with electronics to draw some current. But, I do have the old sensor still, and I'll check it out when I can and let you know. The old tank sensor had the vinyl hose on it, and it was pretty stiff. I decided to replace it to avoid any oiling issues with a cracked oil line.

Again, thank you very much for your input! It is often valuable just to be able to talk to someone about a boating problem; it usually leads to a solution!

Chaparralbob

 

[d.boat]

Re: OMC #175000 VRO Tank Float Switch Question

this stuff is interesting to me. Having just recently obtained and refurbished a VRO/OMS system, I've been messing with it quite a bit. It's a pretty straight forward system, generally within my meager skills and tools, so I found it fun and interesting.