The Ford Barn

mcgarrett · 08-07-2025, 11:04 AM

A friend gifted me with a vintage Heathkit auto analyzer unit. It's in very nice shape and has all the test leads and accessories that came with it along with the instruction manual. My question is, can I use this tester for my 6 volt positive ground vehicles? I would appreciate some guidance from our more electrically gifted colleagues here on The Barn.
(I posted this on the Model A Forum and thought I'd post it here as well.)

petehoovie · 08-07-2025, 11:06 AM

Quote:

Originally Posted by mcgarrett

A friend gifted me with a vintage Heathkit auto analyzer unit. It's in very nice shape and has all the test leads and accessories that came with it along with the instruction manual. My question is, can I use this tester for my 6 volt positive ground vehicles? I would appreciate some guidance from our more electrically gifted colleagues here on The Barn.
(I posted this on the Model A Forum and thought I'd post it here as well.)

hueyhoolihan · 08-07-2025, 11:17 AM

here's a website that may be of some use. it's not as good as AI, but then again, what is, eh? ha

https://antiqueradios.com/forums/viewtopic.php?t=346216

51woodie · 08-07-2025, 01:31 PM

I have one of those "analyzers" as well as a timing light that I built +/- 60 years ago, from kits when Heathkit was in business. I use the analyzer on my 6 volt + ground Coupe, by connecting the leads in the correct polarity.
Point of interest, the timing light has induction pickup off the plug wire.

mcgarrett · 08-07-2025, 01:46 PM

Quote:

Originally Posted by 51woodie

I have one of those "analyzers" as well as a timing light that I built +/- 60 years ago, from kits when Heathkit was in business. I use the analyzer on my 6 volt + ground Coupe, by connecting the leads in the correct polarity.
Point of interest, the timing light has induction pickup off the plug wire.

51woodie,
That's good to know. Thanks for the feedback. The instruction manual makes no mention anywhere about using the analyzer on a positive ground vehicle, but perhaps they assumed the user would automatically know what to do. If I understand you correctly, you're saying to just change the polarity to correspond with a "positive" ground and all will be fine. I'd like to use it for various electrical tests but didn't want to make a mistake and fry something.

hueyhoolihan · 08-07-2025, 03:26 PM

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it's my understanding the most solid-state devices are polarity sensitive due to the use of diodes and that's because diodes are designed to permit the flow of current in only one direction.

recently, i've noticed that some solid state devices are advertised as polarity INsensitive. how they manage that...i have only a guess.

rotorwrench · 08-07-2025, 03:49 PM

Polarity sensitive items need to be connected in like polarity. Positive to positive and negative to negative. Which is power and which is ground is not part of the equation. Only the polarity is relevant. Connecting it the wrong polarity will likely damage it.

Ignition systems are affected by polarity in the way the primary coil is wired. A coil will function with the wrong polarity but the spark efficiency will just be somewhat less. This is why a positive ground system has to have the power connected to the negative side of the coil if so marked. The breaker points are connected to the positive side so in effect, it is properly connected in these systems. A lot of old coils were not marked as positive or negative in the Positive ground era. They were marked SW or IGN for power and DIS for the distributor breaker connection. This is why it's a good idea to have a polarity tester for the old pre 1956 Ford products.

As far as amps are concerned, the ampere meter will register as a discharge amp flow if connected backwards but it won't hurt the ammeter. On a meter that only shows one way then it may not show flow at all if backwards. A generator is not an alternator but both put out a DC voltage. The generator output is DC but the alternator has to be rectified from AC to DC.

mcgarrett · 08-07-2025, 04:21 PM

Rotorwrench,
I appreciate your helpful explanation. As previously stated, I'm electrically challenged to some degree although I do have a pretty good grasp of the basics. For my 6 volt, positive ground cars I would like to use this tester to check things such as coils, condensers, RPM, dwell, voltage, amperes, point resistance, etc. It has settings and instructions for testing all these functions and more. I just want to be sure I connect things correctly without creating a big fireball and smoking the unit.

08-07-2025, 11:17 AM	#3
hueyhoolihan Senior Member Join Date: Dec 2024 Location: central coast california Posts: 255	Re: OT: Question about auto electrical test device here's a website that may be of some use. it's not as good as AI, but then again, what is, eh? ha https://antiqueradios.com/forums/viewtopic.php?t=346216

08-07-2025, 01:31 PM	#4
51woodie Senior Member Join Date: Apr 2018 Location: Chelmsford, ON Canada Posts: 604	Re: OT: Question about auto electrical test device I have one of those "analyzers" as well as a timing light that I built +/- 60 years ago, from kits when Heathkit was in business. I use the analyzer on my 6 volt + ground Coupe, by connecting the leads in the correct polarity. Point of interest, the timing light has induction pickup off the plug wire.

08-07-2025, 03:26 PM	#6
hueyhoolihan Senior Member Join Date: Dec 2024 Location: central coast california Posts: 255	Re: OT: Question about auto electrical test device Sponsored Links (Register now to hide all advertisements) it's my understanding the most solid-state devices are polarity sensitive due to the use of diodes and that's because diodes are designed to permit the flow of current in only one direction. recently, i've noticed that some solid state devices are advertised as polarity INsensitive. how they manage that...i have only a guess.

08-07-2025, 03:49 PM	#7
rotorwrench Senior Member Join Date: Jun 2010 Location: San Antonio, Texas Posts: 17,410	Re: OT: Question about auto electrical test device Polarity sensitive items need to be connected in like polarity. Positive to positive and negative to negative. Which is power and which is ground is not part of the equation. Only the polarity is relevant. Connecting it the wrong polarity will likely damage it. Ignition systems are affected by polarity in the way the primary coil is wired. A coil will function with the wrong polarity but the spark efficiency will just be somewhat less. This is why a positive ground system has to have the power connected to the negative side of the coil if so marked. The breaker points are connected to the positive side so in effect, it is properly connected in these systems. A lot of old coils were not marked as positive or negative in the Positive ground era. They were marked SW or IGN for power and DIS for the distributor breaker connection. This is why it's a good idea to have a polarity tester for the old pre 1956 Ford products. As far as amps are concerned, the ampere meter will register as a discharge amp flow if connected backwards but it won't hurt the ammeter. On a meter that only shows one way then it may not show flow at all if backwards. A generator is not an alternator but both put out a DC voltage. The generator output is DC but the alternator has to be rectified from AC to DC.

08-07-2025, 04:21 PM	#8
mcgarrett Senior Member Join Date: Dec 2013 Location: Corsicana, Texas Posts: 1,306	Re: OT: Question about auto electrical test device Rotorwrench, I appreciate your helpful explanation. As previously stated, I'm electrically challenged to some degree although I do have a pretty good grasp of the basics. For my 6 volt, positive ground cars I would like to use this tester to check things such as coils, condensers, RPM, dwell, voltage, amperes, point resistance, etc. It has settings and instructions for testing all these functions and more. I just want to be sure I connect things correctly without creating a big fireball and smoking the unit.