I think lots of folk are way over thinking some of this stuff, and also using relays more often than what's truly necessary. I was told I needed 3 more relays on my racer many years ago. Funny, everything worked just fine without them, but I ran the proper size wire, had excellent grounds on everything, and even used a stock GM/Chevy stater to fire a 14:1 BBC, hot or cold. I hurt 1 solenoid in over 400 p***es (cheap HD import). Redundancy is expensive. Simplicity is, well, simple. Most every electrical issue I've corrected on old stuff was more ground related than anything. More than relays and complicated systems, import junk is another cause of failure. Now they even recommend a relay on the brake light switch to the back of early master cylinders, the pressure types that "see" brake fluid. Seriously? How about scarfing up all the old ones at swap meets and s**** yards. The part quality is the issue and relay just delays the inevitable. My .02 1/2...
A relay si a electically acitvate switch. It is used for high current draw things like headlights to eliminate lots of current (amps) from having to flow through the mechanical switches. More current caused more heat. That is why older headlight switches have heat sinks on them. Even then, the wires/connecdtors on them show signs of heat damage over the years. My OT car uses relays for the headlights and has the battery in the trunk that uses a Ford type starter relay to send current up to the Gm starter solenoid. Works great in every way.
Correct to a point, but the headlight "heat sink" is simply the resistor used to control the dash lights.......the resistor does create heat, hence the ceramic disc, but it has nothing to do with the headlight current flow through the switch. I do agree that a headlight relay is desirable, and may be necessary, if your build use halogen or HID lamps (I know..not traditional..but effective if you actually want to see something). Ray
I think you may be misunderstanding MadElectrical's point about starter relay. Without a relay, it is true that the starter circuit would have to be wired from the battery through a switch and on to the starter motor windings terminal. That would require one hell of a switch and battery cables running to that switch and back to the starter. That would be heavy, ***bersome and dangerous. Typical automotive starter motors, depending on if they are 6v or 12v, can draw from 200 to 400 amps. So, most vehicles are wired with a realtively light duty ignition/starter switch to OPERATE the relay for the starter. GM starters have had the relay attached to them for several decades. It serves the dual purpose of making contact between the battery and the starter motor and simultaneaously engaging the starter drive with the flywheel teeth. It is 'triggered' by a much smaller current flow from the ign/start switch. Unlike GM, Ford and Mopars for many years used remote relays (not located at the starter motor itself) which served the same purpose of being a heavy duty switch between the battery and starter motor, but DID NOT directly engage the starter drive. The drive unit engaged because of a spiral spline on the starter motor armature shaft. When the starter motor began to spin the drive unit moved outward and engaged the flywheel teeth. When the engine started and revved a bit it 'spun' the starter drive away from the flywheel and back into the at rest position. The question raised in this thread regarding the use of Ford style relays on VW's for example, added a SECOND relay to the system to compenstate for the excessive voltage drop in the stock wiring that resulted in too low voltage to operate the original relay/solenoid. Relays for other parts, i.e. headlights, horn circuit, air conditioning etc., etc., serve the same purpose as the stater relay, only on a smaller scale (lower amp load......though still too much for simple dash switches). Ray
While I understand the drawing's circuit, I DO NOT understand WHY anyone would wire it that way! The relay is unnecessary. The starter motor has a relay attached to it. The "I" terminal, used in the drawing to trigger the starter mounted relay, is normally used to provide 12 volts (actually battery voltage) to the coil as the starter is cranking, as there is volatage drop when the starter is engaged.......and.....the coil is NORMALLY fed through a resistor wire........so when stater engaged, voltage through the resistor drops further and MAY affect coil function....soooooo....the engineers decide to feed the coil full battery voltage during startup to compensate for voltage drop...capeesh? WHY you are putting so much faith in this person's contrarian ideas is something I do not understand. Do you really think the factory engineers have been doing it all wrong for decades? Ray
Hnstray, the argument I've seen for this that makes (some) sense is for a trunk mounted battery. In that scenario it was recommended to have two power feeds from the battery, one which went to a ford solenoid (mounted in the trunk area) to feed the starter and a second one which is fused to charge the battery and supply power to the car. The reasoning behind this is that by doing that you don't have an un-fused high current conductor running the length of the car (except for the brief times when the ford solenoid is activated). Personally I put a mega fuse in the trunk on my car and just ran the one large conductor up to the starter and used the factory solenoid (mopar but similar arrangement to GM). I did manage to pop a fuse when I had the timing messed up and was way too far advanced.
're your post #38.........okay.....I can see the logic of that in the instance of a remote mounted battery........I didn't think of that......"***UMED" battery near starter. Aircraft use a "Master Switch", which is nothing more than a continuous duty relay, for exactly that reason. The battery feed can be shut off for any of several good reasons....no high amp cable through the fuselage from battery to starter or to other high amp loads when not wanted or needed.. Ray
The drawing seems to advocate using a relay to trip a relay; which doesn't make much logical sense. The OP seemed to be describing a relay to operate the stock solenoid trigger lead, which is, again, a relay to operate a relay. IF you have a problem with the stock setup, THEN is the time to consider your options. The first of which should be checking to make sure everything is up-to-snuff. This will eliminate having to listen to crackpots 99.9% of the time. Cosmo
Ok,I gather in my case a starter relay is not needed.At least I understand better what he was talking about.So the purple 14gauge wire activates the Solenoid,which I turns engages starter that has cable attached,right? And MadElectrical just enjoys thinking of places that might needs a relay...
Sounds like you have it right? Does it work when wired up properly? No, on the MAD deal. The relay option is good when a circuit pulls a lot of amperage that you do not want to run thru a switch that might not be capable of handling the load. The switch then only needs to handle the minor load to switch on the relay. Plus, you can locate the relay near the load. Hopefully, you are starting to get the theory.
Ok,I installed a chromed high output alternator on my 1960 Bel Air 235 motor.Used Madds setup.Getting 15volts everywhere I check. I Like the alternator. Is there a resistor that I can buy to step that voltage down to say 13volts?
dtwbcs>>>15volts>>>Is there a resistor that I can buy to step that voltage down to say 13volts?>>> 15 fine. Leave it alone. Jack E/NJ
Agreed. "12 volt" systems are 13.5 to as much as 16 volts, typically 13.5 to 14.5. Likewise, 24 volt aircraft systems are, in reality, more like 28 volt systems. Your house current, and appliances, can be marked 110 v. or 115v or 120v. All within the acceptable range that is delivered by the power company. Ray
Agreed -- I never saw how a Ford relay to a GM starter is going to help anything, merely add one more complication.
I just talked to Mark at MAD Enterprises yesterday. I asked him to explain the starter circuit mentioned in this thread. From what I gather, the remote starter solenoid solves some issues with older cars. -With the remote solenoid mounted near the battery, the battery cable is only hot between the battery and solenoid when driving. The rest of the battery is only hot during starting. This removes any chances of a shorted battery cable while driving. Something I have personally experienced. -In the GM system, the starter solenoid can become heat soaked and the resistance inside the solenoid can be high enough to stop the solenoid from working. Mark quoted a GM study that showed a temperature of 170 F can cause the resistance to increase by 25%. He said he did some experiments of his own and found that GM might have been conservative. This increased resistance happens in components and wires. -In conjunction with the above point. The power to engage the GM starter solenoid travels from the battery to the horn relay to the firewall connector to the ignition switch all in a 12 gauge wire. Then in a 14 gauge wire from the ignition switch to the firewall to the 'S' terminal on the starter. From Mark's explanation the voltage drop can be a couple of volts in a new system and can be much more in an old system with corrosion in any or all of the mentioned connection points. Transient current flow can be 40-50 amps at solenoid engagement!!! With the MAD system the 'S' terminal is jumped to the BAT terminal on the starter and will received full voltage during starting (through the 6 gauge battery cable). The remote start solenoid receives the power that was originally sent to the 'S' terminal, but it only has to operate the solenoid contacts. This current flow will be around 2 amps. -The remote solenoid post with the battery lead attached can also be used as a buss bar location for accessories. The GM junction block by the battery is much smaller and wiring would be neater than attaching to the battery post. -You can also make a switch to activate the starter from under hood as needed for maintenance. As mentioned in other posts, this seems redundant, but after talking to Mark I can ***ure you his methods are sound and he has more experience than I could ever imagine. If you can spare some time, I encourage you to call him. He is very knowledgeable and loves to talk about electrical systems. Make sure your phone is charged and you go to the bathroom. I spent an hour and ten minutes talking to him and he was still going strong. I think Mark said he has spent 50 years in the auto electric business and he seems to have worked with everyone in the hot world of California. He even mentioned talking at length with GM engineers concerning there electrical systems. His web site is full of electrical information and it IS WORTH READING. One note is that his prices on the site are not up to date. Mark has had issues with his hosting company. There is a story about that too. If you dare ask. Bryan
The gist of all this is that if you have a rod that starts ok when cool but has heat soak hot start problems adding a Ford solenoid to the circuit will eliminate the voltage drop thru the wiring from the battery thru the ign. switch ,neutral safety, (you do have one, don't you) & on to the starter solenoid. W/the ford solenoid this circuit only has to trip the ford solenoid which gets its juice from the battery post on the starter & delivers same to the starter switch terminal on the GM solenoid. Yes, it's a band aid but it works in most instances. I've worked on air cooled VWs since the late 60's & have installed many of these band aids. Much cheaper than a new starter & VW owners are renown for being close with a $!
gm hot soak can be fixed with a clean ground path. it's all resistance ie heat. fix the problem dont add more!
"I taught VW Service Schools in the late '60s and in cl*** we would measure the voltage drop on a ch***is on both these circuits.........." I'd say if the voltage drop is less than 0.2 volts or so when the circuit is under full load then there is not much to be gained. And, I'd check each circuit in pieces in case a bum connection or other local problem is causing the voltage drop.
I have had the Batt. in the Trunk on my Race Car since 68 to 75 with No Problems and in my Merc SBC since 73 no Problems I run 200 strand welding Cable from the Batt to the Starter & Ground until have a Problem I will leave it alone it works Very Good like a lot of Guys said before Grounds are the Biggist problems in Cars Just my 3.5 cents
It seems to me that the second solenoid only keeps the battery cable cool. Proper sized battery cables with good connections should be cool already. Them short chunks of welding leads make great jumper cables too.
I bought some stuff from Mark and, as a 1st timer rewiring my car, I learned a lot from him. I used a Rebel harness on my 64 Mercury, and upgraded to a GM alternator, plus installed headlight relays. Basic stuff for you experienced guys but all new to me. He does love to talk and I tried to soak it all in. Wiring project was a complete success. Walt
There is no advantage to doing it this way. All you have done is trigger the engine mounted solenoid from a separate solenoid, with the same size wire that would have come from the key or ****on. If the solenoid or starter was going to drag from heat, it probably still would. I believe the remote solenoid idea works to solve a GM hot-start problem because so much more battery power is transmitted to the starter (and the solenoid thru the buss bar) through the cable. (Which, as stated above is not hot (no juice) until remote solenoid is activated. The small trigger wire will activate the remote solenoid because it is mounted in a cooler place.
Did you look at the diagram closely? Please look at the Furd part. Suppose to be a joke for George Maine! And yes I do agree with what you said.
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