1988 345... The adventure begins!

[Roby466]

I’m wondering about this module... even found a website where they make replacement so maybe I have to check the wire to the sending unit before it goes in that module

[PeterH-350LE]

Originally Posted by Roby466

I’m wondering about this module... even found a website where they make replacement so maybe I have to check the wire to the sending unit before it goes in that moduleAttachment 379096

I would go to the tank and identify the sending unit wire and measure at that point. To the best of my knowledge, its a direct connection from sending unit to gauge, without any module. If you get a good reading at the tank, run a direct temp wire to the gauge.

[Roby466]

Good point, thanks Peter! I will need to find a good gauge though... I’ll see if opening mine may allow for an easy repair but it is questionable with a fallen needle now...

[bkahler]

Originally Posted by PeterH-Airstreamer

I would go to the tank and identify the sending unit wire and measure at that point. To the best of my knowledge, its a direct connection from sending unit to gauge, without any module. If you get a good reading at the tank, run a direct temp wire to the gauge.

Yep, should be a direct run from the sending unit all the way to the "signal" connection on the gauge. As Peter says you should be able to measure resistance of between 0-90 ohms between the signal wire and ground when the signal wire is disconnected from the gauge.

Let me check my stock of gauges, I might have a fuel gauge in there somewhere.

Brad

[PeterH-350LE]

Originally Posted by bkahler

Yep, should be a direct run from the sending unit all the way to the "signal" connection on the gauge. As Peter says you should be able to measure resistance of between 0-90 ohms between the signal wire and ground when the signal wire is disconnected from the gauge.

Let me check my stock of gauges, I might have a fuel gauge in there somewhere.

Brad

Brad, unless you are a teleflex gauge hoarder, your fuel gauge is now in my multi fuel gauge collection.

[Roby466]

Thanks! Let me know if one of you has one for sale. I did cut mine open and put the needle back on and tested with bulbs (1.2W and 21W so 120ohms and 12ohms) and the gauge appears to work for now. One that hasn’t been cut open and is calibrated would be great though . I will go back to the 345 later this week with my multimeter and headlamp and figure out what happened there with that live 12V signal wire. I wonder if a plug didn’t get put back wrong when they did the radiator job.

[Smartstream]

During some of the work on the 345 which is a 1987, I pumped the tank fuel into drums. My gauge always read full with a little needle bounce on occasion. I used the electric pump at the tank and so had the ignition on. I had pumped about 45 gal before the needle moved off full. It seemed to function normally from that point to empty. It seems the biggest problem is the sending unit simply isn't matched to the tank.

[Paul J Mauro]

so funny my fuel gauge has always been sloppy but for 34 years I watch it sit on full and then suddenly drop to half tank.just so far down on my list we live with it.

[bkahler]

Originally Posted by PeterH-Airstreamer

Brad, unless you are a teleflex gauge hoarder, your fuel gauge is now in my multi fuel gauge collection.

I guess if the shoe fits......

[Magnet18]

My fuel gauge works and I intend to replace it soon, if you want it
(bought all new gauges just haven't installed yet)

It is a different visual style though, not sure if it's original

[Roby466]

Great! Thanks!!

[Magnet18]

Here's a pic, doesn't match the telefelexes I don't think

[Roby466]

Brad, if you’re interested in selling one of those they match mine very good. Check your PMs. Thanks!
David

[Roby466]

Did you guys see this guy’s page? He has a module for the fluid levels as per my owner’s manual...
I find it hard to explain why my signal wire to the fuel gauge level has 12 v so while the gauge should have direct connection to the sender, I wonder if this module has a tap in for the low fuel light and may be defective and sending 12v down the signal wire. I’ll see if I can locate it and bypass. Maybe it will stop that 12v signal.


https://theouterlimits.ws/projects/a...sorModule.html

[Magnet18]

Originally Posted by Roby466

Did you guys see this guy’s page? He has a module for the fluid levels as per my owner’s manual...
I find it hard to explain why my signal wire to the fuel gauge level has 12 v so while the gauge should have direct connection to the sender, I wonder if this module has a tap in for the low fuel light and may be defective and sending 12v down the signal wire. I’ll see if I can locate it and bypass. Maybe it will stop that 12v signal.


https://theouterlimits.ws/projects/a...sorModule.html

Yea, that was airforums user WayneG
He made a couple batches of those and sold them on here, not sure if someone like Brad stocked up on spares

OSH park keeps design files, if Wayne elected to make them public they could be found on the site and another batch of circuit boards could be made. From that and his schematics he left on his site, another batch of the boards could be made.

[bkahler]

Originally Posted by Magnet18

Yea, that was airforums user WayneG
He made a couple batches of those and sold them on here, not sure if someone like Brad stocked up on spares

Hmm, second time in a week that I've been called a hoarder! Is it that obvious?

OSH park keeps design files, if Wayne elected to make them public they could be found on the site and another batch of circuit boards could be made. From that and his schematics he left on his site, another batch of the boards could be made.

I don't believe Wayne ever got around to making the second batch. I only received one from him and it's not in my hands anymore.

[PeterH-350LE]

Originally Posted by Roby466

Did you guys see this guy’s page? He has a module for the fluid levels as per my owner’s manual...
I find it hard to explain why my signal wire to the fuel gauge level has 12 v so while the gauge should have direct connection to the sender, I wonder if this module has a tap in for the low fuel light and may be defective and sending 12v down the signal wire. I’ll see if I can locate it and bypass. Maybe it will stop that 12v signal.


https://theouterlimits.ws/projects/a...sorModule.html

David, interesting stuff and so regretful that we lost WayneG. A brilliant guy, indeed! I had no idea that there was a fluid sensor module under the dash.

Not related to your 12v issue, but when I took possession of my 350, some morons wired 12v to the sensor wire thinking it was the internal fuel pump. It fried the sending unit and all I can figure is that the lack of oxygen kept it from blowing up.

So, if you have 12v on the sensor wire, there is a good chance it fried your sending unit and you have to drop the tank. Since you most likely do not have the intank fuel pump, it should be very easy to locate the 2 wires for the sending unit. One should be black, the other purple or brown.

[Roby466]

Thanks Peter... that could very well be related... Hopefully the same thing did not happen and the wiring issue resides in the dashboard (I will remain hopeful for now until I have the chance to get there again and look back there).
I'll report back once I have investigated further. Dropping the tank can't be too much fun I suppose

[Air345Fly]

You don't have to drop the tank, you can cut a hole in the floor
above the fuel level sending unit. That is what I did when I
replaced all of the 34 year old gas line.

You have to cut through the plywood and the aluminum under
floor. I used one of those vibrating saws so as to avoid cutting
too deep. That left a nice square hole. The top of the gas
tank is about 2 inched below the floor so there is little risk
in cutting into the tank.

To put it back, I glued and tacked the cutout aluminum
underfloor to the plywood cutout. I screwed a larger
aluminum sheet on top of the piece of plywood and dropped
it back in the hole. I screwed the aluminum top sheet
around the edge to the floor to hold it down. That
should be good to prevent fumes from coming up.

[Roby466]

Nice! I should look under my bed, maybe someone has been there before and the hole may already be there .

The hole idea makes it much easier as working from the inside is more enjoyable during the winter months...