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| | | | Joined: Jul 2014 Posts: 362 'Bolter | | 'Bolter Joined: Jul 2014 Posts: 362 | Hey guys. Got a '50 Chevy 3100. Have swapped to 12 volts using an alternator, DA plug, etc. All is good...
...Except the gas gauge. It worked fine on 6 volts- has a new tank and sending unit from previous owner. I bought a Runtz from Speedway, used a volt meter to find that the bottom wire is the hot wire, installed it per the instructions included, and the gas gauge doesn't come off E when the key is switched on/off.
It was at around half a tank before I did the conversion. I filled it up this morning. I took the battery out, took the Runtz off and hooked the gauge up like normal, and hooked my battery charger to the battery cables and set it to 6 volts . Gas gauge reads full. I confirmed via test light that the bottom wire on the gauge is hot when the key is on and the top wire is not, hooked the Runtz back up, and have tested different ground locations for the Runtz's little pigtail, and I'm getting nothing on 12 volts, needle isn't even thinking about moving.
Am I missing something? Do I have a bad Runtz?
I searched old posts and a few of you have said you never used a voltage reducer on your gas gauges with no ill effects. Every other source says you need to. I'd rather not ruin a functioning gauge. Sure would like to figure it out... | | | | | Joined: Sep 2001 Posts: 29,269 Bubba - Curmudgeon | | Bubba - Curmudgeon Joined: Sep 2001 Posts: 29,269 |
Which lead on the gauge did you attach the reducer to?
Does the "Runtz" reducer have labelled ends? It is a directional resistor (12v in at a specific terminal and 6v out at the other terminal).
| | | | | Joined: Jul 2014 Posts: 362 'Bolter | | 'Bolter Joined: Jul 2014 Posts: 362 | The Runtz is attached to the bottom post of the gauge, where the hot wire hooks up.
The Runtz is a little flat rectangular thing with a hole at one end and a stud at the other, so it's kind of a one way install- the hole goes over the gauge's post, and the wire goes on the Runtz's post. | | | | | Joined: Jul 2014 Posts: 362 'Bolter | | 'Bolter Joined: Jul 2014 Posts: 362 | Anybody know if there's a way to check the Runtz with a multi meter to tell if it's good or has been damaged somehow? | | | | | Joined: Feb 2002 Posts: 12,029 Cruising in the Passing Lane | | Cruising in the Passing Lane Joined: Feb 2002 Posts: 12,029 | it's a resistor, if it's shorted or open would be a problem, should read a resistance with the ohmmeter, not sure how much but some - likely less than 50 ohms
Bill | | | | | Joined: Mar 2002 Posts: 9,115 'Bolter | | 'Bolter Joined: Mar 2002 Posts: 9,115 | If I remember reading about them, the Runtz is a 3 terminal regulator, not a resistor. That means that the 12 v feed comes in one lead, there must be a ground connected and the output will be your 6 v. I would expect the 6v to appear correctly without any load attached. Your battery charger will not give you a correct 6v for testing, with no load. It will produce peaked sinusoid half wave forms that are much higher than 6 v. | | | | | Joined: Sep 2001 Posts: 29,269 Bubba - Curmudgeon | | Bubba - Curmudgeon Joined: Sep 2001 Posts: 29,269 | Not all Runtz-style solid-state diode-based reducers have 3 terminals. The one from Classic Parts does not and the one for $3.00 does not. All Runtz-resistors are one-way - if installed backwards they either do not work or they fry? The Classic Parts reducer (and many others) are cleverly made so that they can only be installed in the correct orientation. $3.00 - autowire.com $6.00 - Classic Parts (I have one that has been in use for 17 years. $17.99 - speedway motors | | | | | Joined: Feb 2002 Posts: 12,029 Cruising in the Passing Lane | | Cruising in the Passing Lane Joined: Feb 2002 Posts: 12,029 | huh, the $3.00 one is a diode .... all of'em are, why do folks call them "Runtz resistors" if they're "reducers"?? this is the voltage drop resistor I'm familiar with and use .... so yes, hooking those Runtz types up backwards could fry them Bill | | | | | Joined: Jul 2014 Posts: 362 'Bolter | | 'Bolter Joined: Jul 2014 Posts: 362 | | | | | | Joined: Mar 2002 Posts: 9,115 'Bolter | | 'Bolter Joined: Mar 2002 Posts: 9,115 | So that appears to be a three terminal regulator and they describe it as "transistorized".
The ones that are diodes will probably fry the gauge if hooked up backwards, not the diode.
the one that is a gold colour that Speedway sells for 17.99 is actually a resistor. You can buy that from Digi Key for 5.00 for quantities of one. | | | | | Joined: Mar 2002 Posts: 9,115 'Bolter | | 'Bolter Joined: Mar 2002 Posts: 9,115 | I have to comment on the Speedway comment about "Never Ever" use ceramic block reducers on gauges because of power surges. That makes absolutely no sense. However, if they can sell $5 resistors for 17.99 successfully, they know a whole lot more than me! | | | | | Joined: Mar 2002 Posts: 9,115 'Bolter | | 'Bolter Joined: Mar 2002 Posts: 9,115 | I couldn't resist looking it up. Here is where you can buy that same resistor. Resistor from Digi-Key Apparently they cost $4.29. | | | | | Joined: Jul 2014 Posts: 362 'Bolter | | 'Bolter Joined: Jul 2014 Posts: 362 | For anyone who cares, I contacted Speedway, and they sent me another Runtz reducer at no cost. I installed it today, and it seems to be working fine so far.
Last edited by EchoBravoSierra; 09/20/2014 11:47 PM.
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