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Old 10-16-2019, 10:02 AM   #1
thebonecollector
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Question Mechanical Electrical Engineer Expertise Interpretation Please

I consider myself mechanically inclined and have the curse of being able to repair/rebuild/diagnose and just flat out tear things apart to see how they work mindset. Same as a good number of people on here probably, BUT I have had this 1987ish Melex 3 wheel cart for about 10 years now and I cannot comprehend how this speed controlled, Potentiometer, contactor, solenoid microswitch, A2, S1, diode, resistor, series motor monster actually works. My brother and I have studied these many, many different versions of wiring diagrams from multiple sources and manufacturers and electrical specifications including the original Melex manual (and even talked to the guys in Poland at Melex on multiple occasions and still cannot clearly say that we comprehend how this machine operates. Can somebody....anybody please give me a schooling on how the system operates based upon this drawing that I spent hours cleaning up and coloring and studying so I might be able to understand the components and flow of electricity in this cart. I have the battery power, key switch, throttle (potentiometer) and mechanical operation parts down but how the current flows through switches that are not even technically being energized and a speed controller that absorbs excess energy that is fed by a solenoid and protected by a diode and capacitor that somehow tells a motor which way to turn is not clear. Based on the interpretation of this wiring schematic one thing that confuses me is how the Forward micro switch appears to be directly connected to the Reverse Sensing Device and as well how there is No Direct Negative Connection from the batteries to the motor. In my experience you need positive and negative connection to operate a DC motor. The speed controller and the F/R switch is the difference I know. BUT I do not understand the M+ M- A2 S2 S1 Microswitch Solenoid Speed Controller, diode basic functionality. Sorry for the long ramble but this thing is really getting the best of us and currently we are dealing with an upgraded (rebuilt) speed controller to 400 amp from stock 275 amp with new 400-1000AMP Solenoid and 4 smoked microswitches (waiting on 2 more to arrive) right now and just want someone with some expertise to help make us feel smarter than a 5th grader right about now..!
Attached Files
File Type: pdf Colored Electrical circuits.pdf (966.7 KB, 0 views)
File Type: pdf The Melex Bush Blind.pdf (103.0 KB, 0 views)
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Old 10-18-2019, 02:35 PM   #2
thebonecollector
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Default Re: Mechanical Electrical Engineer Expertise Interpretation Please

Again I am at the end of the rope of this one so I appreciate your information. In regard to the #3 response. This drawing that I have color coded to try and match the color of the wires on our cart is actually a schematic directly out of the Melex manual. I did not change or alter the drawing only cleaned it up and added the color. The GREEN wire was the wire for the reverse sensing device or back up beeper. I did remove the beeper itself and then just made it a direct connection basically to the smaller - post on the solenoid. You are exactly correct though. After we got the new microswitches installed on the F/R Switch and turned the Key switch ON nothing happened UNTIL we moved the Forward Reverse switch to FORWARD position and the Diode blew instantly. We have not done anything yet as it has been so frustrating with all of this we did not know what we damaged now. I have ordered two more microswitches not knowing if they were blown because we have our annual trip coming up next week that we have been doing for the last 30 years and I wanted to make sure I had replacement switches on the way. We have new diodes and pre-charged resistors as well. this will be the 4th set of microswitches on the F/R switch that we have had to replace. We are about at such a state of defeat to a point of giving up. We need the cart so I am hoping for the Hail Mary at this point. I am attaching a copy of the original drawing that came from Melex to show that we are basically connecting everything just as they have it on drawing. I am also attaching a drawing that we made where we think that the wires go based upon the Melex wiring diagram. I don't know if this will help or make things more confusing but I am throwing everything out there.
Attached Files
File Type: pdf Electrical Fig 11 1 7.pdf (212.7 KB, 0 views)
File Type: pdf Redrawing of Davids Hand Drawing.pdf (50.0 KB, 0 views)
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Old 10-18-2019, 04:42 PM   #3
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Default Mechanical Electrical Engineer Expertise Interpretation Please

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Old 10-18-2019, 06:51 PM   #4
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Default Re: Mechanical Electrical Engineer Expertise Interpretation Please

I posted this reply in the other thread since the info was relevant to the thread. I'll post it here as well, and continue the conversation here from this point.

Quote:
The GREEN wire was the wire for the reverse sensing device or back up beeper. I did remove the beeper itself and then just made it a direct connection basically to the smaller - post on the solenoid. You are exactly correct though. After we got the new microswitches installed on the F/R Switch and turned the Key switch ON nothing happened UNTIL we moved the Forward Reverse switch to FORWARD position and the Diode blew instantly.
Right, Jumping the green wire directly together removes the resistance from that circuit, which essentially makes it a direct short when the switch is actuated. I don't think this fried your diode, but I'll get to that in a second.
If the reverse buzzer did not work, or you just want to remove it, then you should remove the wire that supplies power to the reverse microswitch.

You mentioned you installed a new solenoid, so you had to remove the diode from the old solenoid, and install it on the new one correct? It's possible you installed the diode backwards which would have fried it as soon as the switches closed to send power to the solenoid. When you install the New Diode make sure the Band on the diode is Towards the Positive Side of the solenoid.
Second thing about the solenoid, What brand and model number solenoid did you install?
Some of the higher amp solenoids do have a polarity to the solenoid coil (small terminals) and that polarity has to be correct when you connect the positive and negative wires to the solenoid or else it will smoke the diode and possibly ruin the solenoid. Those solenoids will have + and - marked on the terminals, so double check that before connecting the wires to it.

In your second re-drawn diagram you are missing the wire from the Pot Box to the solenoid. The Key switch gives power to the F/R microswitch, the micro sends power to another micro switch inside the pot box, which I will call the "Throttle Microswitch". The throttle micro switch then sends power to the small positive terminal of the solenoid. This is designed so the solenoid does not engage until you have the Key On, F or R selected, and Press the throttle, so that you have three steps before the cart is able to move.
Double check the wiring for that circuit on your cart. Make sure it matches the Melex diagram.
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Old 10-19-2019, 10:08 AM   #5
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Default Re: Mechanical Electrical Engineer Expertise Interpretation Please

Thank you. We are getting somewhere and that is great. I am waiting on our last set of microswitches to try and get this to work for our trip next week. I want to make sure I understand the comment in your #3 from your first response. You say that in my drawing there is a switch on the RIGHT that seems to be drawing power from the B+ terminal at the solenoid via GREEN wire. I am attaching the same drawing that only has the GREEN wire colored. The micro switch that this is referencing is from the F/R switch control. It is however the switch on the LEFT and it did go to the back up beeper which I removed and wired direct to what I thought was the SMALL post on the solenoid and on the NEGATIVE side of the solenoid. Am I understanding the drawing correctly? I think that the LARGE TERMINALS on the solenoid are the Posts on the top labeled N and L standing for NEUTRAL AND LOAD. The positive Pack + cable is going direct to the N side of the TOP Post on the solenoid. The SMALL posts on the solenoid are on the bottom I am understanding and the NEGATIVE side of the small posts of the solenoid is the RIGHT side under the L Large post. Is this correct? How i see this circuit flowing is that the GREEN wire is coming from the NC side of the Forward Micro Switch and it went to the back up beeper and then to the negative side of the solenoid at the small post it then went from there to the SPEED CONTROLLER to the B- which is in fact the Pack Main NEGATIVE. This is the only GREEN wire that I have in my drawing. Is this how you are seeing this? When I removed that back up beeper I just took that wire and connected it direct to the negative side of the solenoid at the small post. I did that so that the reverse sensing circuit would still be there in the event that the controller required that circuit as part of its processing.
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File Type: jpg Reverse Sensing Circuit.jpg (120.2 KB, 0 views)
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Old 10-21-2019, 08:10 AM   #6
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Default Re: Mechanical Electrical Engineer Expertise Interpretation Please

Hang in there TBC someone will be along to help you
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Old 10-21-2019, 09:50 AM   #7
thebonecollector
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Default Re: Mechanical Electrical Engineer Expertise Interpretation Please

I have something backward to the solenoid because it blew the last two switches instantly when my brother put the forward reverse lever into FORWARD. Switches are not easy to find and we are on our 4th set and expensive. I am trying to relay information to my brother in another state. I don't even have the cart in front of me. The first time after he put the new solenoid in and rebuilt controller the cart worked but the direction was reversed. Forward went back and Backward went Forward. He then decided to switch the wires at the Solenoid rather than the motor. Both switches blew out. He replace them and we started trying to wire the cart by the Melex diagram. Next set of switches he installed after he used meter to test all of the components including the diode and resistor he turned key on, put the cart in Forward and when he stepped on the pedal it blew the diode I believe AND the two new microswitches. Next set of switches that he put in after waiting another week for delivery (yea been doing this for about a month now) he turned on the key and put the cart in Forward and SNAP!! blew that set of switches. Like I said we are on the last set of switches that he should get today in the mail. Come somebody provide some much needed help here. This is the last go before we get together in Missouri for our annual outting. Here are some more pictures and diagrams because obviously we can't get this thing back to rolling. I know I know he should have taken more pictures before. We thought that we had enough to cover the limited wires (we thought) and get this thing back together. We have had this thing for at least 10 years and have replaced everything now in the engine compartment including rebuilding the motor..potentiometer, wires, controller, solenoids. Only thing not replaced is the key switch.
Attached Images
File Type: jpg Collage for BGW.jpg (55.5 KB, 0 views)
File Type: jpg Carts Unlimited Solenoid.jpg (76.6 KB, 0 views)
File Type: jpg Collage for BGW page 1.jpg (77.8 KB, 0 views)
File Type: jpg Collage for BGW Page 2.jpg (59.4 KB, 0 views)
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Old 10-21-2019, 10:38 AM   #8
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Default Re: Mechanical Electrical Engineer Expertise Interpretation Please

Sorry, so many questions with nobody getting a chance to answer. Maybe this will help make it easier to answer.
Attached Files
File Type: pdf BGW Question about GREEN WIRE connections.pdf (589.5 KB, 0 views)

Last edited by thebonecollector; 10-21-2019 at 10:40 AM.. Reason: No attachment
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Old 10-21-2019, 10:56 AM   #9
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Default Re: Mechanical Electrical Engineer Expertise Interpretation Please

First, there is no green wire from your solenoid small post going to the FNR.

When You turn the Key switch ON, You have positive power (blue line) on micro-switch #15 and the Controller activation C on the Controller.

When the FNR is in either Forward or Reverse position, positive power goes from micro-switch #15 to the Pedal micro-switch #11.

When You press the pedal, the pedal micro-switch #11 completes the positive power to the Solenoid in order to activate it.

The negative power activation for the Solenoid is always present since it is directly connected to Controller B-.

The FNR micro-switch #14 is only used to activate the reverse buzzer and it can be removed.

You can either follow the wires connected to it and disconnect them at the source or just place electrical tape on the disconnected wires to prevent a short circuit.

The same applies to the reverse buzzer, either tape the wires or follow them and disconnect them for the source.
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Old 10-21-2019, 01:17 PM   #10
thebonecollector
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Default Re: Mechanical Electrical Engineer Expertise Interpretation Please

Wow...that is crazy. That micro switch 14's only purpose is to activate the reverse beeper?? that would have taken me a LONG time to diagnose that. What about the wire that is going from that microswitch 14 up to the LARGE post on the solenoid that is the same post where the Main RED + cable is connected from the battery? What is that circuit if I remove the microswitch won't it affect that or is it just getting the power through it to activate the reverse beeper?
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