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Old 07-24-2012, 05:15 PM   #1
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Troubleshooting the MicroMonitor

Well, after I installed the Horst Miracle probes I thought I was done with this issue, but while my black tank works perfectly (still) my gray tank is reading full all the time. Since I was assured my Horst probes were impossible to fail due to gunk in the tank I assumed I had a MicroMonitor problem.

Used the MicroMonitor trouble shooting guide (attached) and hit a wall. So I called Terry at KIB Enterprises (KIB Enterprises - Excellence in Electronics) and we went through all the steps to eliminate the MicroMonitor and its components one more time.

What was really interesting was the way the system lights the lights. I thought that the top probe would turn on the full light (all of them) and the 2/3 probe would light 3, etc. I knew the empty light is the "power available" indicator and not really in indication of what is going on in the tank.

So, for the techies out there:

The red wire from the control panel passes 8 volts DC when the tank selector is pressed to the resistor pack (a red plastic lump with 4 wires coming out of it called a K101 pigtail). If there is no current path to ground the OPAMPS in the monitor circuit board do not fire to turn on the 1/3, 2/3, FULL LEDs.

If the lowest probe (all things working perfectly - Yellow wire) has a path to ground the 8 volts is dropped across a 188K resistor dropping the line voltage from 8 to 6 volts. This drop fires one opamp turning on the 1/3 LED. As the water rises and the 2nd probe is covered, an additional 68K is added to the circuit dropping the line voltage to around 4 volts. This fires another opamp turning on the 2/3 LED. The full probe is a direct connection to ground and the voltage drops to 2 volts or less, lighting all the LEDs.

What is interesting is that if the 1/3 (or the 2/3 for that matter) probe gets contaminated with crud (gray tank soap, or grease), for instance the conductance of the crud on the probe and wall to the ground probe is added to the circuit reducing the voltage as if the probes above it were covered when they are fine.

(WARNING - DO NOT DO THIS TEST WITH THE FRESH TANK - different circuits)

Not that it matters, but you can actually determine which probe is actually "bad" by removing all the wires from the three probes on the right and connecting them one at a time to the ground probe. The lights should come one properly is the system is working as advertised.

The solution, since it is the probes in my case, now involves finding out if I can clean them without damaging my Horst Mircale probes. I have contacted (but not gotten an answer yet) the maker of the Horst probes to see if a Gallon of "Simple Green" dumped into the gray tank (and then fill it with water) will dissolve the crud without dissolving the probes.

If they do not get back to me, I am just going to give it a shot before I order a new set. (Film at Eleven...)
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Old 07-25-2012, 08:24 AM   #2
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Got a call back from Susie at Horst Probes.
She suggested washing the tank out with ... wait for it ....

1/2 cup of Calgon Liquid Water Softener and a not sudsing soap, then drive around for a while. I replied again about a more aggressive technique and will let you know what she says.
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Old 07-25-2012, 10:07 AM   #3
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Quote:
Originally Posted by herk7769
Got a call back from Susie at Horst Probes.
She suggested washing the tank out with ... wait for it ....

1/2 cup of Calgon Liquid Water Softener and a not sudsing soap, then drive around for a while. I replied again about a more aggressive technique and will let you know what she says.
She's checking with forest river forum for a solution for you.
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Old 07-31-2012, 04:32 PM   #4
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No dice. The ZEP purple degreaser stripped off some of the grease on the walls but not all of it. The resistance increased enough to turn off the FULL light but the 2/3 light and below are still on.

Next step is to pull and clean the probes and try to wash the walls with a long bottle brush. I will be ordering another set just in case they don't go in easily.
The OEM probes are not reusable. I hope the miracle probes are...

DW and I are going to have a long talk about oil and grease in the kitchen drain.
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Old 07-31-2012, 05:38 PM   #5
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DW and I are going to have a long talk about oil and grease in the kitchen drain.
And when that talk is over, Lou will say "Yes maam, I understand" and order another set of probes.

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Old 07-31-2012, 08:41 PM   #6
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And when that talk is over, Lou will say "Yes maam, I understand" and order another set of probes.

<sigh> Most likely.
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Old 08-05-2012, 10:42 AM   #7
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Lou, I have a Charleston and my three bottom lights come on, the top light blinks when the grey button is pushed. I replace the 4 sensors and the same thing. I remove the yellow, green and orange. Same thing three bottom are on and top blinks. From what you are saying the board is bad. Joe A.
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Old 08-05-2012, 04:28 PM   #8
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Lou, I have a Charleston and my three bottom lights come on, the top light blinks when the grey button is pushed. I replace the 4 sensors and the same thing. I remove the yellow, green and orange. Same thing three bottom are on and top blinks. From what you are saying the board is bad. Joe A.
Joe, From "FULL" (all 4 lights) - ONE 72 hour treatment with RV-Digest-It and no driving (the recommended way of "washing the tank walls") and I have increased the probe resistance when empty to only the 1/3 light being on. Resistance less than 188K Ohms.

I have NO idea what got dumped into the kitchen sink (I am thinking bacon grease, but she ain't sayin'), but RV-Digest-It is taking care of it. The gray tank is once again full with 8 oz of RV-Digest-It and will sit for another 72 hours before I dump it again. My hope is the last of the grease will be gone by then.
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Old 08-05-2012, 05:10 PM   #9
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I'm thinking I sure wouldn't approach her again with the bacon grease theory. You might have been an L/C but wife always is the ranking person at home. Your's in not to question why. LOL Been there, done that, have the Tee shirt.
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Old 08-05-2012, 05:30 PM   #10
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I'm thinking I sure wouldn't approach her again with the bacon grease theory. You might have been an L/C but wife always is the ranking person at home. Your's in not to question why. LOL Been there, done that, have the Tee shirt.
You are right, of course. But this is the first time my "normal routine" has caused a probe problem since the Horst Probes went in. Black tank is STILL perfect after 2 years.
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