Fuel gauge fried

[RedBay]

I installed my rebuilt fuel gauge today , but it did not work , still stuck on empty so I switched the sender cables but nothing , so I disconnected the voltage reducer as I read that some dont use it

and now it moved up to full but only for a few seconds , some smoke and back down to empty, so what did I do wrong ?  

Edited December 5, 2015 by RedBay

[ptwothree]

You runnin' 6 or 12 volts?

[RedBay]

12 volts.

[ptwothree]

I'm not an expert on these 2 wire systems, but, I can tell you that the terminal marked "10" needs to have 6 volts at it when the ignition key is in the on position.

 

Running 12 volts thru this gauge might not be a good thing. If you have a shop manual  the gauge, a power source, a sender, or a variable resistor, this could be bench tested before actual installation.

 

These gauges have a lot of stuff in them that the later 1 wire gauge don't have....so more stuff to go wrong.  I like your wiring harness, looks nice.

 

Btw,  the book says if you reverse the #1 an 2 wire the gauge will read differently but will not damage the gauge.

 

What you need is a 2 wire expert to help out....I'd like to know the how's an why's of these things too...and I don't even own one!

 

GL....

[RedBay]

Ok , I got the impression that a few guys here  do not use  the 12 to 6 volt reducer for the gas gauge even though they have converted to 12 volt and the  gauge did not get damaged so that’s why I bypassed the voltage reducer just to see if it was going to give any readings, but doing so I clearly damage my fuel gauge , I have two voltage reducers and both of them give me zero volt outgoing , so today I went to Radio shack to get a new 7805, 12 to 5 volt reducer .

It would be nice if any of you guys running 12 volt to your fuel gauge could confirm that, thank you.

Edited December 5, 2015 by RedBay

[RedBay]

I found this and it looks like it should be possible to at least for a short time connect 12 volt to the fuel gauge 

http://p15-d24.com/topic/38274-running-6-volt-gas-gauge-on-12-volts/?hl=volt

[dpollo]

Sure, it is possible to run the gauge on 12 volts but when you double the voltage, current through the same resistance goes up  approximately  4 times.

This may shorten the life of the gauge and the sender   I recall that there is also a condenser on the back of the 48's fuel gauge

maybe that is what went up in smoke.

I have found that a light bulb about the size and wattage as a dash light or marker light makes a viable and cheap resistance tp limit the current in the gauge circuit.  wire it between the ignition switch and the gauge.   It  can be a 12 volt bulb and will glow about half brightness.  This works well on 49 and up, but I cannot be sure about 39-48

[T120]

Sure, it is possible to run the gauge on 12 volts but when you double the voltage, current through the same resistance goes up  approximately  4 times.

 

I believe it is more correct to say the current is doubled and the power is 4 times...

Edited December 6, 2015 by Ralph D25cpe

[ptwothree]

so today I went to Radio shack to get a new 7805, 12 to 5 volt reducer .

It would be nice if any of you guys running 12 volt to your fuel gauge could confirm that, thank you.

Ok...6 volt gauges were designed to operate at 6 volts.  Gauges are voltage sensitive as far as accuracy is concerned.  Along comes 12 volt systems and now there is enough voltage headroom to make these things more accurate.  This is done with a voltage regulator that knocks a variable 12 volts down to a constant 5 volts.  

 

So now the gauge has 5 volts to it on one side and a variable resistor, the tank sender, on the other.  Now all the gauge has to do is figure out the diff between the constant applied voltage to the incoming resistance from the tank.  

 

I just replaced a non working regulator in my  60's car that controlled both the fuel and temp gauges with a 7805 solid state regulator mounted to a small heat sink.  Solved the problem and both gauges work as they should.

 

Your gauge has a pair of heated and a pair of non heated "blades" that, I think, because the book is not clear on this, regulate voltage to make the gauge see an average of 6 volts.  

 

It sounds like you are going to need another gauge that is known to work and 6 volts to run it.

 

Note for the Menses out there...this explanation of regulators vs. 6 and 12 volts is not intended as a Collage course in Electronics...Only to get a working gas gauge working again.

[Andydodge]

I have run my car on 12 volts since 1973 when I hot-rodded it, the fuel guage is the stock, original 1940 Dodge guage with a 12volt resistor wired into its power source, the guage has worked since, although I'd have to say that its not the most accurate instrument around but generally reads correctly full, empty and in between..........dunno if this helps.............andyd

[RedBay]

Thanks guys , I am sure it was the gauge and not the condenser that went up in smoke , you can see the melt down in the photo, I have another gauge, it does not work either so I have to send it for a checkup. not to Bobs this time as it took 10 weeks and $250 before I could install it .

[RedBay]

Hi guys , just installed my fuel gauge , repaired by Instrument service Inc. Machesney Park IL, but I have a problem , after one minute the gauge shows 3/4 and everything is fine but after 2 minutes gauge drops to empty.

I installed a new sender but same story , so I wrote to the repair shop and this is there answer

 

"Our techs said you should have a 10 to 73 ohm sending unit for your vehicle.  We are not familiar with the voltage regulator (7805) that you are using.  The one we use is different. Thanks, Lori Instrument Services, Inc.

 

I have two sending units and both are 30 ohms ? is 10 to 73 ohms for 1949 and up ?

[RedBay]

another answer from the repair company

 

 

" Our techs checked the meter that was in the gauge when we received it.  It was a 10-73 ohm meter.  We put a new meter in it that was also a 10-73 ohm meter.  We have a voltage regulator that we use.  They are $80.00.  Thanks, Lori Instrument Services, Inc.

[Plymouthy Adams]

if your speaking in regard to what is stock and proper for your Plymouth....30 ohms across the two terminals is correct..but when wired, each leg splits the 30 ohms to ground which is the wiper (float arm)...deal with a company that is familiar with the thermo style gauge and you may be well ahead of the game for time, effort and money.

[RedBay]

another answer from the same company

 

"The meter that was in your gauge was tested and read 10-73 ohms, so that is what was put in.  If you use a sending that is the same ohms the gauge should work for you. However if you are on a 12v system, you will still need the correct voltage regulator.  If you have any other questions, you may call us.  Thanks, Lori Instrument Services, Inc.

 

only me that believe that they made a mistake installing/converting my gauge to  10-73 ohms ? and that they  now are blaming me for sending them a 1948 10-73 ohms gauge ?

[RedBay]

if your speaking in regard to what is stock and proper for your Plymouth....30 ohms across the two terminals is correct..but when wired, each leg splits the 30 ohms to ground which is the wiper (float arm)...deal with a company that is familiar with the thermo style gauge and you may be well ahead of the game for time, effort and money.

but the repair guys are now telling me that my fuel gauge after repair now is a 10-73 gauge !! my sending units are both 30 ohms . and they are asking me to buy another sending unit that is 10-73 , but is that any such sending units on the market for a 1948 plymouth ?

[Plymouthy Adams]

it is this simple...the very company has modified your car's gauge to operate outside the parameters that are stock...in doing so and not telling you in advance would in my opinion put you in line for a refund as they sold you an item/repair not compatible with your car nor did it seem they informed you prior to said repair that you would need to also upgrade/change your sender.  You can discuss this here all day but in truth, you need to exact either a refund or compatible sender from the company that you have already spent good money with that who's product is of no use to you at this time.

[Seaside Pete]

I installed my rebuilt fuel gauge today , but it did not work , still stuck on empty so I switched the sender cables but nothing , so I disconnected the voltage reducer as I read that some dont use it

and now it moved up to full but only for a few seconds , some smoke and back down to empty, so what did I do wrong ?  

 

 

 

Although I have covered this subject before, I notice in your last picture that the live feed on your gauge goes to the center nut/terminal, whereas mine goes to the bottom left nut/terminal so which one is correct? this may be your problem or indeed my problem. When I purchased my new tank and sender from tanks inc they listed a single pole sender not a 2 pole sender with a 10 - 73 resistance. After contacting them to check if this was correct they confirmed yes a 10 - 73 is correct for all mopars of this age. I have a 47 P15. I have attached a pic of the back of my gauge and although you cannot see it clearly the live feed goes to the bottom left nut, I am though going to use a 12v to 6v converter that will handle up to 10 amps.

 

Any advice would be helpful.

 

Pete

 

 

 

[RedBay]

 

photo of my gauge showes 1 upper left 2 upper right connects to tank unit,  ignition to center, -1948 2 pol 30 ohms 1949- 1 pol 73 ohms  

Edited March 2, 2016 by RedBay

[RedBay]

it is this simple...the very company has modified your car's gauge to operate outside the parameters that are stock...in doing so and not telling you in advance would in my opinion put you in line for a refund as they sold you an item/repair not compatible with your car nor did it seem they informed you prior to said repair that you would need to also upgrade/change your sender.  You can discuss this here all day but in truth, you need to exact either a refund or compatible sender from the company that you have already spent good money with that who's product is of no use to you at this time.

stay away from these clowns,  Instrument service Inc. Machesney Park IL, they are not responding 

[Dodgeb4ya]

As shown above 6 Volt feed is to the lower left with the radio supressor installed.

Needs to be hooked up right.

Edited March 4, 2016 by Dodgeb4ya

[Seaside Pete]

Ah! it would appear there are 2 types then mine is like Dodgeb4ya whereas RedBay's does not have the bottom left connector. At least I know my gauge is connected right.

 

Thanks for the pics DodgeB

 

Pete

[RedBay]

recieved another answer from Instrument Service Inc.

 

 

"Good Morning:

According to our repair manuals for the gauge and sender, the correct ohms and sender are 10-73 ohms.  The gauge was hooked up to our 6v reducer prior to shipping back and it worked properly. If you would like to discuss this further, please call us at 800-558-2674. The emails that you have received have been sent by Lori(Office Manager) and John(Manufacturing Manager).  Thanks, Lori Instrument Services, Inc. "

[Plymouthy Adams]

they are going on a very late 49 first series or the second series 49 forward..not for your thermo sensitive gauge..

[Dodgeb4ya]

Ah! it would appear there are 2 types then mine is like Dodgeb4ya whereas RedBay's does not have the bottom left connector. At least I know my gauge is connected right.

 

Thanks for the pics DodgeB

 

Pete

I think his condenser assembly has been modified. That black shiny wire to ground is new.