Dash sensor modules schematic

[Keyair]

Just checked. That is it.
I cut it out.
Some wires were disconnected anyway.

[WayneG]

That one should be the fluid sensor module.
here is a closeup of my dash schematic showing the wiring colors.

I guess crimping was Airstreams "cheap way out" to connect the dash components. I would have used connectors, and I did do that for my rebuild.

[Keyair]

Wayne,
Electronics are black magic to me, so how do you reverse engineer something like this, that is “Potted” in resin????

[WayneG]

Originally Posted by Keyair

Wayne,
Electronics are black magic to me, so how do you reverse engineer something like this, that is “Potted” in resin????

That is where it gets tricky. If it is a dead module then caution is not as critical.
The bulk of the epoxy can be gouged out and I have solvents that work to dissolve epoxy or I can use heat to help soften and chip away the remainder around the components.
All 3 of these procedures have a fair probability of wrecking the circuitry in a good module, that is why I would prefer to not like to play with one that works.
If lucky, there may be silk screening on the PCB board inside the module that hints at the component values, otherwise if the parts are not marked there will be a lot of guessing and measuring of component values and transistor specs.

I work (semi-retired) in a nuclear accelerator laboratory in a University where many of the things we work on are ancient and parts are no longer available, so we have to get creative to duplicate the functions.

[Keyair]

Ok. Pm me your address and I will send you this one!

[WayneG]

Originally Posted by Keyair

Ok. Pm me your address and I will send you this one!

PM sent

[Keyair]

Got it.
This module is bad I think.
Lights that are on on my dash include:
Water in fuel
Coolant level.
Washer fluid level.

I will get it in the mail to you ASAP!

[WayneG]

Originally Posted by Keyair

Got it.
This module is bad I think.
Lights that are on on my dash include:
Water in fuel
Coolant level.
Washer fluid level.

I will get it in the mail to you ASAP!

I will be looking for it and get it in the shop for reverse engineering.
BTW those are the same lights that come on on mine but intermittently.
I tried everything outside the module to cure it and nothing has worked so I think it must be a design flaw in the module. The Po on mine just taped over those dash lights, that is not my style.

[Keyair]

It’s going in the mail today.

[Keyair]

Mailed. Will be with you Friday.
Will pm you the tracking #.

FYI, the one wire with the connector on it in this pic was not connected to anything and the connector was not crimped on the other side, never had been, so my guess would be that’s the Water in Fuel feed! [emoji50]

[WayneG]

Yes, the gray wire is for the water in fuel sensor that is not installed in the gas engine version. I assume it could be used for some other sensor if needed.
When it gets here, I will bring it to work to start operating on it, see what makes it tick and clone it.

[Keyair]

Awesome!
I, for one would love to see photographs and a description of the process.

Will you just post the schematic or actually make them for others?

[WayneG]

Originally Posted by Keyair

Awesome!
I, for one would love to see photographs and a description of the process.

Will you just post the schematic or actually make them for others?

I will try and do both. I dont expect it to be too complicated or expensive to reproduce. I dont think I will see surface mount or exotic components or multi layer circuit boards, but this is 80's gear, sometimes there can be surprises.

[WayneG]

It just arrived. The wires look the same colors of mine, it looks like the potting cup is a bit larger than what they use on mine, I expect all the functions to be the same.
I will bring it to work Sunday or Monday for a closer look. I will also bring my camera for some photos

[Keyair]

Sweet!
As stated, I broke a section on the frame.
Next time I am over, I will try to locate the pressure module!
Could it be the unit I posted originally?

[WayneG]

To avoid filling up my attachment space I started a temp webpage for that:

http://theouterlimits.ws/projects/ai...sorModule.html

I only had a few hours to work on it today but it looks like it will be a easy disassembly.
I used a bandsaw to remove the plastic shell. I was happy to find the epoxy did not cover the bottom of the circuit board due to a air pocket.


I also found that this epoxy degrades and crystallizes at a very low temperature using a low heat torch, so scraping the epoxy off is easy, but it will be time consuming going around the components.

By the looks of the circuit board, there are at least 2 IC's on it, and they have similar connections, so I am guessing there are 2 sensor circuits on each IC.
There are 10 large round connections, I assume they are for the 10 wires.

Before I get much farther with epoxy removal, I am going to design a build a tester to simulate the operation in the MH. I will be out of town for a few days and I will start that later this week.

[Keyair]

Great stuff!

[WayneG]

A little more progress today from home. Since I am getting close to components that I dont want to burn, I am using hot water to remove the epoxy. It is slower, but it works.
I dip the board into water that is just below boiling point for 10 to 15 seconds, pull it out and start chipping epoxy.
They did not make it easy, the poured some granules, similar to fine aquarium gravel, on the circuit board. That makes it harder to chip out the epoxy from around the parts.
I worked on it for about 3 hours today and this is how far I got:


I am also working up a schematic and circuit board layout as shown here:


I found the IC's are TTL inverters that I think they are using in a oscillator circuit that is similar to other fluid sensors I found online. I need to get the rest of the components ID'd before I know for sure.

[Keyair]

Wow!
If there was a Nobel Prize for Airstream Electronics, I’d be voting for you!

[Keyair]

Home now, but still amazed at your update!
In addition...
I have some history in resins, GRP, and molding work.
Back in this time period, it was not unusual to use sawdust, wood chips, wool flock, gravel, pebbles, rags, and whatever else that was cheap and to hand, as a filler in resin, to save materials, and therefore $.
This has been replaced with micro spheres and dedicated fillers for resin.