Reed Style Fuel Level Sender

[plateaucal]

I think what he is trying to say is either take a class in Electrical Engineering 201 (first circuits class) or go to Ace hardware and pick up three foot wooden dowel for $2.50.

[plateaucal]

All jesting aside, the late model fuel gauge is a completely different animal from the early one. As with all late model Patrol's the accountants took over. The late model gauge uses a bi-metallic arm wrapped by a thermo-electric wire. The heating of the wire varies according to the current which is controlled by the resistance of the fuel sender. The bi-mettalic fuel indicating arm then bends according to the current induced heating. The gauge regulator purpose appears to be related to the innate voltage (thus current) variability of the alternator. The regulator opens and closes in order to maintain a consistent level of current to the bi-metallic arm, thus prevent the fuel gauge from constantly following voltage. The temperature gauge is regulated as well.

Having seen an early fuel gauge (which is now in L60Boerne's possession), it is truly a different and more complex mechanism. I do remember that incorporates some kind of coil, or solenoid like structure. The delicate nature of the beast precluded further investigation.

It seems that someone needs to measure the resistance of this new part compared to an OEM part, across it's range. If it is not right on the simple addition of another resistor may be necessary (either in series or parrallel). Now, it's been 40 years since EE201 for me, but I could probably pull it off. However, there is a man on this board that appears to have the knowledge. His name is Robert Moore.

[zed]

As with all late model Patrol's the accountants took over.

Why must the decisions of the engineers be blamed on accountants. I know of at least 100 accountants and I’d bet my Patrol none know how to use a multimeter.

Keith

[plateaucal]

As with all late model Patrol's the accountants took over.

Why must the decisions of the engineers be blamed on accountants. I know of at least 100 accountants and I’d bet my Patrol none know how to use a multimeter.

Keith

They all drive German cars so you may have something there. However, there was some serious cheapening going on in final iteration of the Patrol. Engineers are like cops; they do what they are told.

[L60Boerne]

Thank you JW for allowing me a test run on a unit. In the back of my mind I recall RiverPatrol saying that gauge clusters with voltage regulators (66.5 yr model and later) will not work with my older style wiring. That is all I know and that may only apply to the connections but it may also apply to the voltage regulator in terms of the signal?

Hopefully someone will chime in soon on this. Regardless , you did a good job having these made.

Santa's Sleigh is back in King Kong Craig's shop today, though he has moved on, getting fully serviced ahead of the our wild bull hunt this weekend. The bad news is that I got interested too late to get a jerry can holder in time for mounting it so we will need to carry the extra fuel in the receiver mounted cargo basket.

I will have some great pictures I would like to upload but I need to re=learn how to do that with my current phone.

Patrolloing in Alpine soon,
L60Boerne

[Johnny Roadkill]

It seems that someone needs to measure the resistance of this new part compared to an OEM part, across it's range. If it is not right on the simple addition of another resistor may be necessary (either in series or parrallel). .

Yes, that. If the resistance is the same it doesn't matter if the gauge uses a bimetallic strip, a coil or a wet stick.

Adding a simple resistor is unlikely to yield a good result...in series it will work only if the original sender characteristic has the same 90 ohm span but lower resistance at the empty and full endpoints, in parallel it will produce a non-linearity in the characteristic which would be a total fluke if it worked right.

Sorry if that's vague...me, vague ? just making clear the known and unknown elements so I wouldn't be misinterpreted.

Cheers,
D

[Esteban]

In 2014 member moore_rb measured the resistance of both type of senders. In the posts there are also comments and math done by faux40 in case someone wants to review.

http://www.60patrol.com/forum/viewtopic ... bc63eddb14

These are the readings by Robert:
Ok, here's what the ohm meter came up with for the senders:

The newer style (the top one in the photo farther up the page) reads 100 ohms at "Full" and about 20 ohms at "empty"

The older style sender (bottom) reads 90 ohms at Full, and 10 ohms at Empty.

The pictures he refers are gone They were from Photobucket

[plateaucal]

The new one is 10 -100. Close enough eh? Usually people want to know when they are near empty. When you are full you usually know it. I'll explain later it gets complicated.

[Johnny Roadkill]

These are the readings by Robert:
Ok, here's what the ohm meter came up with for the senders:

The newer style (the top one in the photo farther up the page) reads 100 ohms at "Full" and about 20 ohms at "empty"

The older style sender (bottom) reads 90 ohms at Full, and 10 ohms at Empty.

mmm...data - thanks Esteban and Robert ...now we can actually work this out...and the good news is that after throwing some numbers into this, simple resistor modifications will probably work ok, despite what I said earlier the non-linearity issue is pretty insignificant...I'll wear that one.

New style gauge with the aftermarket sender - will read full when the tank is full, and will read empty with ~10% fuel left. Only other issue is whether the gauge will be electrically or mechanically damaged when the actual fuel level is empty and the sender is at 10 ohms...could use a 10 ohm resistor in series to fix that issue but then the gauge will read full at ~90% fuel in the tank and the gauge needle will try to push beyond the full mark with more than ~90% fuel in the tank...to fix that add an 1100 ohm resistor (or combination of 100 ohm + 1000 ohm in series) in parallel across the combined sender and 10 ohm resistor and that should work pretty well (100 ohms full, 19.64 ohms empty).

Old style gauge with aftermarket sender - will read empty when the tank is empty, and full at ~90% fuel in the tank. Adding a ~900 ohm (910 is a standard value) resistor in parallel with the sender would probably work pretty well there (90.10 ohms full, 9.89 ohms empty with 910 ohm resistor in parallel).

These values should be more than close enough given the OEM sender and gauge characteristics probably have significant variations from unit to unit.

Cheers,
D

[plateaucal]

Okay, dun deal. After re-thinking this thing. The purpose of the strange little voltage regulator on the newer models may be to prevent the needle from pegging out. Because I forgot to mention the regulator is nearly identical to the gauge in that it used a bimetallic arm wrapped by a thermoelectric wire to open and close the contacts. I rebuilt mine, but it was like brain surgery.... as I remember.