Jump to content
dmorales-bello

Perplexing "FUEL" light malfunction

Recommended Posts

Does the serial number correspond to the information on the website description?
Good idea. I'll check and post.

Sent from my SM-N950U using Tapatalk

Share this post


Link to post
Share on other sites

went to the JY today (yea no cover charge!) and found a 1991 Toyota, 4 door sedan, the tank sending unit was easy to get at so I pulled it and found the same style thermistor but it was inside a plastic holding tank (like 2 oz size). removed it and ran some test. It was pretty grody so I sprayed some electronics cleaner in it  but could not get the light to go out unless I sprayed the cleaner direction into the tiny holes. I used some fine wire to open them up but I think there is still junk inside that is causing issues with getting the fluid in and out.

I ended up opening two holes (top and bottom) to about 1/16" with a drill, now it works reliably. will post up the video in a few. I wanted to see if warm fluid (in my case water since I don't want to smell up the house with gas) would keep it from coming on so I used hot tap water, about 110f.

 

Edited by Dave WM
  • Like 1

Share this post


Link to post
Share on other sites

I was able to peel down a strip of the can to get a better look, while I was not able to focus the IR gun on the tiny thermistor (looks like the size of a 1/8 watt resistor) I was able to hear it hiss as I dunked it in the water. 

From what I can see it seemed to have a dark burned looking band in the middle. Further test show its resistance to be polarity sensitive at least with the DVM. It would range from 1.6k to 2k just by swapping leads. the VOM did not seem to notice it but being analog and the scale pretty small it may have moved a bit. the VOM showed something like 1.7k as did the VTVM. I suspect the solid state nature of the device may be a factor in this. I am not sure if I can salvage the thermistor with out destroying it, at this point the can is toast so I would have to if I wanted it in a uncompromised can. Not a big deal but would be fun to try.

another interesting observation was at 1st I was unable to get any resistance reading with the DVM, it would just toggle between moHms and koHms, not settling on a scale (auto ranging DVM) I did not have this issue with either of the fix range VOM or VTVM. After a few min (maybe when it had cooled down as I tested right after using it in the light circuit) I was able to get the 1.6-2k readings (depending on polarity) with the auto ranging DVM.

Edited by Dave WM

Share this post


Link to post
Share on other sites

some of the harvesting and transplanting operation. I pigtailed the remnants from the hot side of the can inserted one lead of the thermistor, crushed and then soldered. Removed the old filter material (copper weave I think) soaked in vinegar to remove the scale, then reassembled soldered up the other lead to the can. The OE can works much better as far as getting the fluid in and out of the can.

 

100_1999.JPG

100_2001.JPG

100_2004.JPG

100_2005.JPG

100_2006.JPG

I am going to clean and touch up that solder on the bottom. I thought I had the lead cleaned and tinned but it looks like it could be better.

Edited by Dave WM

Share this post


Link to post
Share on other sites

Maybe they are designed to drain and fill slowly so that the light does not go on and off as I described earlier, from gas sloshing around. 

 

The little gas pump/robot symbol light came on, were running out of gas!  Wait, it's off...  It's on again!  Nope...wait...

Share this post


Link to post
Share on other sites

some of the harvesting and transplanting operation. I pigtailed the remnants from the hot side of the can inserted one lead of the thermistor, crushed and then soldered. Removed the old filter material (copper weave I think) soaked in vinegar to remove the scale, then reassembled soldered up the other lead to the can. The OE can works much better as far as getting the fluid in and out of the can.
 
100_1999.thumb.JPG.562a45d02974499a12e5099c88487dc4.JPG
100_2001.thumb.JPG.87820a467c992b1eb7425c6c38e67c15.JPG
100_2004.thumb.JPG.04d1b5a98b09bc84af3263c7b64962f4.JPG
100_2005.thumb.JPG.a2eb0be5323217d9185b0bb9072c501a.JPG
100_2006.thumb.JPG.237c7843307c28f27093ead40dc4fbfe.JPG
I am going to clean and touch up that solder on the bottom. I thought I had the lead cleaned and tinned but it looks like it could be better.
Amazing, delicate work, Dave! So... does it work?

Sent from my SM-N950U using Tapatalk

Share this post


Link to post
Share on other sites

very well so far I will post up a video tomorrow demo of it working. Right now I am testing by letting is set in water for an extended period of time, monitoring the current (it seems to idle at about 30ma when submerged). One thing that is different is the fact that the donor had a rather elaborate plastic container (the before mentioned 2oz plastic container) This container was mounted on a wire just like the stock Datsun ( a stiff wire to the mount flange). I can only assume the OE Datsun was designed to operate with out said container, perhaps that has something to do with the hole size etc...

I did not notice any filter media on the plastic container, but then again I did not look at it too closely. The OE Datsun unit drained VERY quickly.

Edited by Dave WM

Share this post


Link to post
Share on other sites

Do you need two bulbs, more resistance, with that Toyota thermistor also?

image.png

Edited by Zed Head

Share this post


Link to post
Share on other sites

No offense to Dave, but is there more info here than for the ZCD thermistor?  I'm looking for that set of DIY parts that a person could put together on their own.

If he used just one bulb would he have the same problem that the ZCD sensor has?

Share this post


Link to post
Share on other sites

I checked all the available information on each one of the 5 bulbs I'm running the tests on. The number imprinted on the base of the bulbs does not coincide (with two exceptions) with the number assigned to it on the company's web site or on their sales receipt. However I think I was able to match them by cross referencing information and images. Remember that I assigned numbers 1 through 6 to the bulbs related to their measured cold resistance in descending order. "Glow" is subjective and refers to the perceived intensity of illumination when the erroneous signal is triggered by the Zcar Depot thermistor. Here's the full info on each bulb:

Bulb #______Volts______Watts_____Amps_____Resistance_____Glow_____#on base______#online___

1                     14               1.12            0.08             19.8                      +               756                    9428049

2                     14.4            1.44            0.1               12.7                      ++             813                    813

3                     14.4            1.728          0.12             11.5                      ++            1445                  274020

4                     14.4            1.872          0.35             11.4                      +++          1892                 274004

5                     14                2.8              0.2                 6.3                      ++++         363                   363

6  (OEM)        12                3.4                ?                   3.8                     +++++       NA                    NA

 

Bulb 6 has been ruled out since it illuminates very brightly when triggered.

Bulb 5 Illuminates more softly but is still barely visible in a dark cabin. Could work as a "monitor" of the system in working order (see previous posts).

Bulb 4 illuminates softly enough when triggered that it is not visible during daylight and very hard to see in the darkened cabin. If it brightens enough once the fuel level falls beneath the thermistor, then this bulb would be a reasonable and simple solution to the problem. I'll report on that once my tank is empty.

Bulbs 3, 2 and 1 have yet to be tested but they might illuminate too dimly to be effective as a low fuel warning once triggered by the thermistor even when the tank is empty.

Edited by dmorales-bello

Share this post


Link to post
Share on other sites
27 minutes ago, Zed Head said:

No offense to Dave, but is there more info here than for the ZCD thermistor?  I'm looking for that set of DIY parts that a person could put together on their own.

If he used just one bulb would he have the same problem that the ZCD sensor has?

That's an excellent question. It seems from all our musings and experiments that the thermistor has to be appropriately matched to a specific enough bulb for the system to work properly.

Share this post


Link to post
Share on other sites

more results,

yes the bulbs are GE47 (standard 6.3 volt used in most vintage electronics, series connection results in approx. same resistance as the bulb in the fuel indicator light.

late Saturday night experiment was disappointing. While the setup worked perfectly at 1st (out of water light comes on quickly 30s or so, in water light goes out within 1 second), continued testing showed that if left in the water for an extended period (in my case 45 min) the light was on. It was somewhere between 15 min and 45min when the light came on (I was not watching constantly).

while monitoring it I noticed the mA slowly going up, I incorrectly assumed it would stop at some point as it entered a steady state of water temp. Wrong. I left it at 15 min at about 60mA up from starting at 30ma. Came back at 45min and I was up to 190ma an bulbs lit.

Oddly I could not get the lights to go off even after blasting it with contact cleaner (very cold), Thinking I had destroyed the thermistor I considered an autopsy but decided to bag it for the night just in case I was missing something obvious. oh and the resistance was fixed think about 200 ohms but cant recall.

Next day everything is back to normal, hmmm, same working comes on out of water goes out in water. Thinking maybe I should test in fuel rather than water JIC it makes a diff (surface tension, cooling effect, etc...) so this time I use some fuel, works as expected, on out of gas, off in gas. left it go for at least 45 min, still off in gas, lift it up, goes on quickly, back in gas off again.

I also had this gas rigged up with a heat source to elevate the gas temp to upwards of 130f. Thinking it would not be uncommon for the gas in the tank to be  warm. No effect works fine.

Right now I am testing again with the intent to operate for hours with warm gas and see if it stays off.

I will post up the videos I on the testing later today after the long term test is complete. I think I will also try the test with just one light (the 6.3v) just to see how sensitive the choice of the bulb is (big change from 2 bulbs in series to a single bulb), after I complete the long term test that is.

 

 

 

Edited by Dave WM

Share this post


Link to post
Share on other sites
16 hours ago, dmorales-bello said:

That's an excellent question. It seems from all our musings and experiments that the thermistor has to be appropriately matched to a specific enough bulb for the system to work properly.

I will be addressing this specifically. IF my long term test are successful with the current testing using the 2 GE47 6.3v series bulbs, I will remove on bulb from the series (that's a drastic change) and see how the system works. I will be posting an interim video in a few mins to set the stage.

 

Edited by Dave WM

Share this post


Link to post
Share on other sites
17 hours ago, Zed Head said:

No offense to Dave, but is there more info here than for the ZCD thermistor?  I'm looking for that set of DIY parts that a person could put together on their own.

 

not really. but I will test the system to see just how sensitive the setup is. IF it turns out that a wide range of bulbs works then perhaps we can assume that maybe its not as critical as it may seem. in which case a simple resistance/physical size may be enough. I may end up just buying the specific thermisor referenced by some of the motorcycle guys to test as well. that will give us an exact part number to use. At this point I just want to see if I can replicate the prob Dr. Dave is having.

Edited by Dave WM

Share this post


Link to post
Share on other sites

What I am also wondering is the thermistors use in a circuit. Was the later model stuff (like the 91 Toyota) really just the same deal a simple bulb/battery/thermistor setup like the Datsun OR was it more complicated perhaps a latching relay or some transistor bias adjustment or such... anyway testing will continue.

I kinda like the idea of a latching relay, trigged on just like the bulb, but once on break the current flow to the thermistor, leave the light on until the ign key is turned off to reset the latch. This take the thermistor out of the high heat for an extended time as well after the latch is set.

for more reliable that the relay perhaps and SCR could be triggered by the thermistor. I like it since once triggered like the latching relay, it would stay on until the ign key was turned off.

Edited by Dave WM

Share this post


Link to post
Share on other sites

after about 1.5 hours (and no lite, about 30mA) I have shorted out one of the GE47's now my current is about 40mA, fuel temp about 118f, will monitor to see if things remain stable (lite off).

Share this post


Link to post
Share on other sites

Just finished testing. Results are in. works the same with one or two lights (in series). That is it stays off in gas (warmed to about 118f) but will come on within seconds of removal of the sensor from the gasoline. I had to cut the on time short for the single bulb as I did not want to overload the filament. Based on my test I can definitively say that it works with either one or two GE47 bulbs. Are they the same as the stock unit, no, but I feel the cover a broad enough range that its safe to say the circuit should work with a low amp 12v bulb. the GE47 is approx. 1 watt at 6v from what I can find.

The only other test I can think of is to try the setup in the car (I will set it up on the floor board and directly connect to the factory light). I will set that up later today and report back I have a video coming on the test I just reported on.

below is a few hours later. What I am not clear on is I tested it for well over 1 hr with 2 bulbs and then well over 1hr with a single bulb. The overall current was pretty much the same, I suppose due to the ratio of the bulb resistance to the thermistor resistance. The only diff was if I had allowed it to go on much longer on the single 6v bulb I suspect it would have burned out.

Another observation, when testing with water vs gasoline, the thermistor can dumped MUCH faster with gas vs water. I suspect a surface tension issue.

Las thing, I forgot the thermistor was in warm gas when I checked the resistance, about 1k I took it out sprayed out the warm gas cooled with the solvent it was over 2k, I suspect when it settles down to room temp (aprox 78f inside the house AC) it will return to the 1.7kish resistance.

 

Edited by Dave WM
  • Like 1

Share this post


Link to post
Share on other sites

So basically your summary is that the Toyota thermistor works great, but the ZCD part does not. And not only that, but the Toyota thermistor seems to work great* with two wildly different bulbs.

Did I get that right?   LOL

 

 

* Assuming you don't leave it on so long that you fry your 6V bulb by applying 12V to it.

Share this post


Link to post
Share on other sites
1 minute ago, Captain Obvious said:

So basically your summary is that the Toyota thermistor works great, but the ZCD part does not. And not only that, but the Toyota thermistor seems to work great* with two wildly different bulbs.

Did I get that right?   LOL

 

 

* Assuming you don't leave it on so long that you fry your 6V bulb by applying 12V to it.

in a nut shell..

:)

Tomorrows test will involve using the light bulb that is installed in the Z, which I presume is nothing special, same as all the other OE dash bulbs.

Edited by Dave WM

Share this post


Link to post
Share on other sites

Got it.

Dr. Dave, Did you drill out the holes in the ZCD version yet to see if getting more flow in there helps? I'm still not yet convinced this is a completely electrical issue.

If you're reluctant to make modifications to a unit that you still might want to return, you could possibly simulate larger holes by encouraging flow? Read... "Wave it around in a cup of liquid (to try to force fluid through the little holes) while monitoring the state of the lamp."

Share this post


Link to post
Share on other sites
25 minutes ago, Dave WM said:

 the light bulb that is installed in the Z, which I presume is nothing special, same as all the other OE dash bulbs.

Yup. Most of them should all be the same. The glove box might be the easiest to get to if you just want to pull a bulb. That or maybe the ashtray bulb?

Thought of something though... After all the years and PO's though, you should make sure you've got the right bulb. Original is Toshiba A12V3.4. There are other numbers that have been used over the years as replacements, but if you find that Toshiba bulb, you know you've got an original.

Edited by Captain Obvious

Share this post


Link to post
Share on other sites

That plastic piece just has to be for locating and protecting.  It's just slipped in after the thermistor is fed in to the can and the wire is soldered to the bottom.  Give it a tug.  It will probably slide right out and expose the thermistor. 

image.png

image.png

Share this post


Link to post
Share on other sites
Got it.
Dr. Dave, Did you drill out the holes in the ZCD version yet to see if getting more flow in there helps? I'm still not yet convinced this is a completely electrical issue.
If you're reluctant to make modifications to a unit that you still might want to return, you could possibly simulate larger holes by encouraging flow? Read... "Wave it around in a cup of liquid (to try to force fluid through the little holes) while monitoring the state of the lamp."
Yes, I did. I carefully enlarged the hole in the middle of the white plastic cap at the top with a fine Dremel burr, and enlarged the three holes in the bottom of the can with a 1/16 drill bit on the Dremel. I performed the "dunk" test in water before and after the mods and flow into and out of the can definitely improved.
That modded unit is in my gas tank now and unfortunately produced the same malfunction as before enlarging the holes. I'm testing the different bulbs on it as reported in my previous post.
I think the "trapped air bubble" theory for the malfunction can be discarded. At this point, with all the tests@Dave WM and I have run, the most probable cause is that the ZCD thermistors in both units I received are not adequate for this application.
Attached are pics of the enlarged holes.
20d2666c219c960ab9b5c993dad85274.jpg

Sent from my SM-N950U using Tapatalk

Share this post


Link to post
Share on other sites

what is interesting to note is the thermistor did exactly what Dr Dave had when I used water (just in case that got lost in all my post). I attribute this to poor fluid flow perhaps due to surface tension. If Dr. Dave wants to try it I will be happy to send him this one, I would like to test a bit more, but at this point the best test would be to install in a car that has a top loader (mine is a side loader). If it does not work in Dr Daves  car would assume he is driving around with 1/2 tank of water.

 If she weighs the same as a duck then she is a witch (a man of science) .

 

Edited by Dave WM
  • Like 1

Share this post


Link to post
Share on other sites

Create an account or sign in to comment

You need to be a member in order to leave a comment

Create an account

Sign up for a new account in our community. It's easy!

Register a new account

Sign in

Already have an account? Sign in here.

Sign In Now

×
×
  • Create New...

Important Information

By using this site, you agree to our Terms of Use. We have placed cookies on your device to help make this website better. You can adjust your cookie settings, otherwise we'll assume you're okay to continue.