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Posted By Discussion Topic: Positive ground logic? -- page: 1 2     Jeepbut 01-28-2017 @ 7:19 PM reply profile send p.m. Member Posts: 76 Joined: Jan 2017 What is the theory or purpose of positive ground? what is different in the system to make it positive ground? Old Henry 01-28-2017 @ 9:40 PM reply profile send p.m. Senior Posts: 738 Joined: Apr 2010 Don't know why early cars were positive ground but most electrical components in the car don't care, they'll work fine either way. The only three that I can think of that matter is the vibrator in a stock radio that will only work with positive ground, the battery gauge reads backwards if switched to negative ground, and the generator has to be re-polarized if switched to negative ground. When I first got my car back on the road after sitting 31 years I knew nothing about positive ground. So, when I installed a new battery, I hooked it up negative ground like my modern cars were. Everything worked fine except the battery gauge read backwards. It wasn't until I got the engine rebuilt after 10,000 miles that the rebuilder said, "You know you have your battery installed backwards? Bet your battery gauge reads backwards." After the rebuild all I had to do was re-polarize the generator to positive ground and everything worked fine. wmsteed 01-29-2017 @ 11:19 AM reply profile send p.m. Senior Posts: 613 Joined: Oct 2009 The early electrical systems were generally positive ground. As I recall Thomas Edison advocated for DC whereas George Westinghouse advocated for AC power. There was a third player in the early power game, Tesla who was an advocate of DC power. Generally the big difference between the two systems is that DC has good power over a short distance, however, it needs constant boosting via coils/transformers. DC power requires larger wire for transmission, whereas AC power can be transmitted over greater distances with smaller wire and less boosting. Surprisingly the phone systems are all DC power which is hot all of the time. The phone is turned off/on by breaking the ground, (positive). Many of the circuits that are employed in automotive uses are controlled by breaking the ground. interior lights are the most common, the switch actually controls the ground. Electricity is some very strange stuff, almost like smoke and mirrors. When I was in the US Army I was in Fire Control, ie; the systems that controlled the direction/elevation of anti aircraft weapons up to huge 155/120mm canons. These huge weapons were operated by 28v DC over hydraulic motor systems. I guess the difference in positive, negative ground could be summed up that when negative is used as a ground, breaking that connection permanently disconnects that circuit, whereas alternating current using positive as the ground is not totally disconnected.. Bill 36 5 win delx cpe len47merc 01-29-2017 @ 12:37 PM reply profile send p.m. Senior Posts: 1165 Joined: Oct 2013 Jeepbut - your question has been asked many times on this Forum. I recalled an earlier, compelling response on this posted by TomO that gave me the best insight for further reading that may help you. All credit to Tom - I cut and paste his words here: "Ford, Chrysler, Cadillac, Oldsmobile, Pontiac, Nash, Hudson, Frazer, and Studebaker were all positive ground at some time in the 30s. Cadillac changed to NEG ground in 1946, but the Ford, Chrysler, Nash, Studebaker and Packard all stayed with the POS ground system. Nearly all of the cars in the late 20's and 30's were POS ground, so Ford was not in the minority. Most 6 volt cars were POS ground until they changed over to 12 volts. Packard stayed at POS ground even after the change. I have heard that it had to do with how current flowed in the system. Some engineers believed that because current flowed from POS to NEG, that POS ground was more effective. Others thought because electron flow is from NEG to POS, that NEG ground was more effective. In practice, it makes little difference which side id grounded. Tom" Do a search for 'positive ground' for 'All' history on all Forums and you'll find much more on this including the Edison/Ford relationship that may have also contributed to the positive ground design. Steve 51f1 01-29-2017 @ 2:23 PM reply profile send p.m. Senior Posts: 573 Joined: Oct 2009 This is what I recall about positive grounds: In the old days, some cars had positive grounds to help minimize corrosion. Automotive wiring was insulated with cloth and, usually, with some type of paint like varnish added for extra protection. Of course, the cloth based insulation absorbed moisture which allowed the electricity to “leak” through the insulation to ground. Electrical leakage promoted the formation of corrosion on the metal car body and frame. Some people thought that, when the ground was positive, the corrosion was reduced, so they used positive grounds. Of course, people working on cars during the early days were not well educated and did not have the research to back them up, and, in my opinion, they were probably wrong. Later, in automotive history, and, with the advent of the transistor, the electronics industry standardized on the negative ground. When electronics proliferated, the ground was switched to negative to match the electronics industry standard. At the same time, the insulation on the wiring was improved. Richard TomO 01-30-2017 @ 7:40 AM reply profile send p.m. Senior Posts: 7250 Joined: Oct 2009 POS grounding also had to do with metal transfer on the electrodes of the spark plugs and the points. Read the Ford Shop Theory Manual for a good explanation of the thoughts back in the day. I had never heard the leaky wire corrosion theory before. It sound like it may have come from England where the wires in a Lucas system leak smoke. Tom MG 01-30-2017 @ 10:40 AM reply profile send p.m. Senior Posts: 1254 Joined: Nov 2009 wmsteed said: "Tesla who was an advocate of DC power." - Tesla was certainly NOT an advocate of DC power. Tesla teamed up with Westinghouse to promote AC. Tesla is best known for his contributions to the design of the modern alternating current (AC) electricity supply system. "The War of Currents (sometimes called, War of the Currents or Battle of Currents) was a series of events surrounding the introduction of competing electric power transmission systems in the late 1880s and early 1890s including commercial competition, a debate over electrical safety, and a media/propaganda campaign that grew out of it, with the main players being the direct current (DC) based Edison Electric Light Company and the alternating current (AC) based Westinghouse Electric Company." Jeepbut 01-31-2017 @ 7:08 PM reply profile send p.m. Member Posts: 76 Joined: Jan 2017 This has been interesting. Thanks to all. engine 02-04-2017 @ 9:16 AM reply profile send p.m. New Member Posts: 103 Joined: Dec 2012 I have a 1968 Triumph motorcycle and it has a positive ground system as well. It is a English bike 51f1 02-08-2017 @ 5:25 PM reply profile send p.m. Senior Posts: 573 Joined: Oct 2009 (Thomas) Edison was an advocate for DC power. (Nikola) Tesla was an advocate for AC power. If Edison had prevailed, we'd have a DC power plant on every corner as DC cannot be practically transmitted over long distances. Tesla should get more credit. Long distance transmission requires high voltages to overcome resistance losses. There is no practical way to increase DC to the voltages that would make long distance DC transmission economical and then lower it to a more useful (and safe) working voltage. Transformers only work with AC; therefore, AC can be easily transformed up for transmission and down for the user. Edison gets way too much credit in my opinion. Edison was a tinkerer, not a scientist. Tesla was an engineer. They did name a car after him. What did they name after Edison? Richard This message was edited by 51f1 on 2-8-17 @ 5:27 PM

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