Tanks Level Gages on older trailers

[perryg114]

Anyone messed around with the tank level gages on the old trailers say late 70's to early 80's models. I have a couple LED's out and would like to get them fixed. I am assuming that the tank monitor measures the resistance between the electrodes and ground and when the fluid level covers one of the electrodes an LED comes on. I am trying to figure out if it is a readout problem or a tank wiring problem.

Perry

[idroba]

I may be out to lunch on this but my experience with many 70's Airstream tank sensors is that no matter how much you fool around with them, they just don't work very well if at all. They give very general information when they do operate, such as the tank is more than 1/4 full and less than 1/2 full. I just never bothered with them after a while.

I know that is not the information you wanted on repair, it is just a general observation.

[perryg114]

I did some looking through manuals and found a 78 manual that had the led tank monitor as opposed to the analog ones on the older trailers. Checking is pretty easy. You pull the panel and short the ground pin to the sensor your checking. If the electronics are good then the led will light. If you find a bad one, it is either the opp amp chip or the led it self. To figure out which, jumper the a lit diode to the bad one and if both are lit then it is the opp amp chip. I have a bad channel on one opp amp chip and one bad led. You can also jumper at the tank to test wires just like you do on the back of the board.

Perry

[perryg114]

Ok I finally got my problems fixed. I replaced and opp amp chip with a new one and replaced one bad LED. I fixed a few loose solder joints as well. Well the board tested good shorting the ground pin (brown wire of each array) to one of the sensor wires. There will be the ground pin and 4 wires on each tank gage. Mine has three tanks. I still was showing the 3/4 full gage on the black and gray tanks as not working. I removed my newely installed access panel (a result of changing out the valves). I shorted the ground to the"full" sensor and the 3/4 full LED lit up. I intended to short to the 3/4 full sensor. I then put more water in the tank I was messing with and eventually the 3/4 LED lit up. The full led was lit prior to this. I thought at first a bad sensor but what happened was 32 years ago someone switched both the black and gray tank sensors for full and 3/4 full. I even looked at the plug where the tank sensors are plugged in and the had the pins crossed in the connector.This was a factory defect. I just swapped the two sensors on the control panel and everything works. All sensors work and light and unlight in the proper order. I now have more tank capacity because I was getting a full indication at 3/4 full. I looked like the 3/4 indicator was bad but it just wired wrong.


Perry

[idroba]

glad you were able to sort it out, and hope it continues to work for you.

[thomdial]

Perry,
I have a 79 Safari, and the gauges work fine.However, when I installed a new freshwater tank, it had one less electrode, so I have to extrapolate a little between 1/2 and full.

[perryg114]

Well I hope mine will last another 30 yrs. At least I know how to repair and trouble shoot it.

Perry

[Mixter]

Hey Perry- I've got the old analog control center in my '76. I found a couple of the LED styles for cheap, that have the LPG readout too. I believe them to be early 80's Excella panels. One has LPG and the other does not.

I bought them cheap, hoping that I could retro fit one into my remodel. That said, I was reviewing the project last night trying to make some sense of the existing wiring in the coach, and where they would possibly go on the Excella panel. I quickly realized that I have no idea how these probes work, and how the wiring works on these control panels.

Any chance you have a wiring diagram and more helpful info on this project?

As a backup plan, I have identified the See Level II as a possible complete replacement for the whole thing.... For now, I can visualize a complete replacement as a possibility if I can figure out the factory stuff...

Along that line of thought.... "SHOULD" I be using the See Level with the external, stick on tank indicators? I never even knew those existed. Not sure how they work. All along I have been planning on using the original probes. When I had my tanks out, I cleaned them, including the probes, and resealed them back in. I guess if I abort the original system, they are nice and sealed.....

Any help is appreciated!
Mic

[Zeppelinium]

More than you ever want to know about tank monitors:

http://www.airforums.com/forums/f443...tal-58532.html

and a more modern microprocessor based version:

http://www.airforums.com/forums/f443...or-113265.html

Zep

[perryg114]

You might be able to use the other boards but you are going to have to do some research. It sounds like Zep is the man on this. I think I have a shop manual from 1977 if there are schematics that you need from that era let me know. I don't have the schematic for my 81 model. My tank sensors have two wires at the bottom of the tank. I am assuming that one is a ground and the other is the empty tank sensor. There or 3 or 4 more senors going up the tank.

Perry

[Mixter]

Wow.... that's alot to digest... I have to admit, I'm trying to follow all that circuitry, but totally lost

I have a '76, with original gray and black tanks. I can't remember how many probes/ wires. I also replaced my original Fresh tank with one out of a '75 because the original was badly cracked and not usable. I know it has a different amount of probes/wires than the originals do.

Here is my Control Panel- it is different than all the ones on the posts.

I'm not sure I'm familiar enough with this stuff to try and retrofit, and the See Level II is sounding easier for me to understand.

Zep are you making yours for sale?

Anyone have experience with the See Level with the stick on sensors?