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MG MG Y Type positive to negative BBS discussion at MG-Cars.info
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MG MG Y Type - positive to negative
| hello i,m thinking of changing my yb to negative earth has anyone any views on this and would anyone have details on how it,s done thanks john |
| jr dennis |
| John Is there any particular reason you want to do this? It is reasonably straightforward to do ... but you have to ask yourself why you might want to do this. Do not just do it because "everything else in the world is the other way round". One of the reasons often miscited for this being a "good thing to do" is that it makes the car less prone to rust. That is simply not true. Steel will rust at the same rate whether you pass current through it ... or not - at least as far as our lifetime goes. So, is there another reason - you want to fit a CD player, cell phone charger, nitros boost pump, bouncing suspension pump, electric windows, ghetto blasting sound system etc.? Otherwise, frankly I would bother. That said though, some people want to do this and I was looking through some old stuff the other day that was covering this so I may well dig it up again and put it in the Technical Centre so it is on file - for completion's sake if nothing else. If you need this sooner, let me know and I'll move it up my workload. Paul |
| Paul Barrow |
| John Here is a link to the article anyway - http://www.spritespot.com/Downloads/Positive%20to%20Negative%20Ground%20Conversion.pdf and I am in the process of getting permission for us to add it to our site. Paul |
| Paul Barrow |
| Providing there are no components which is polarity sensitive such as a radio or electronic ignition [ensure there are no suppression diodes fitted] etc, it is only a matter of reversing the battery connection and then touching the small stud field terminal of the dynamo with a +ve supply [it will spark]. I converted my YA and 105e Anglia many years ago and more recently my TF. More recently there has been some discussion regarding the ignition coil connections, but my cars have run for years with no degradation in performance. I stand corrected but as far as I understand the coil is not polarity sensitive at least my ones are not. |
| B Mellem |
| O! I nearly forgot, the ammeter connection must be reversed otherwise it will show a healthy discharge when the engine is started and the lighting load a charge. |
| B Mellem |
| I would also get a couple of signs saying "This vehicle is NEGATIVE ground" for the inside and outsite of the battery box. I seem to remember MOSS Motors carry these in their MGB Catalogue range so this can be made to look professional. This will also help any one working on the car who is used to expecting these cars to be POSITIVE ground - like I would for instance. Paul |
| Paul Barrow |
| paul and mr mellem thanks for your reply still can,t decide i am also thinking of fitting an alternator and remote servo i would appreciate your comments john |
| jr dennis |
| John You cannot fit an alternator without converting to Negative Ground, so that is a fairly easy one to cover. As to fitting a servo, my personal opinion (which others may feel free to contradict) but if your brakes are properly and regularly adjusted, your brake shoes in good condition, your fluid changed regularly, you drive within the design parameters of the manufacturer (and dont try to be silly with it) and bear in mind that other motorists and pedestrians have seen UFOs and space Aliens before they saw a Y Type, then the original braking system of the Y is more than adequate to stop you. In all of my years (is it 12 already) since I got my Y, it has never failed to stop me adequately and in a safe distance ... without a servo, and on cross-ply/bias ply tires. And yes I do drive it hard, and yes I do drive in the rain too. Like I say though - this is just my personal opinion. Paul |
| Paul Barrow |
| An excellent article on fitting an alternator can be found at http://ttypes.org/ttt2/ford-alternator-conversion-on-a-t-type. The principles and steps are easily mimiced on a Y Type. Paul |
| Paul Barrow |
| One thing to note if you change your Y or YB to negative earth is that the battery leads dont fit as the round posts (on the type of battery fitted) have different diameters. This is the main reason I did not bother to convert my YB as I had bought new leads for the positive earth system. |
| D MULLEN |
| If its any reassurance I have several times in the past thrashed my YA over the Alpes with a caravan on the tow bar, and never experienced brake fade although I always treated the descents with care especially the mountain passes. John you are the proud owner of a fine motor car! Bryan |
| B Mellem |
| Hi Paul, that link gets me a 404 error "not found on this server". |
| Remo Peter |
| Hi all,
Any hints about traps for young players would be appreciated. I am currently (no pun intended) rewiring my dash board. Because I have some polarity sensitive bits, I will be converting to negative ground. Which raises some questions for me. I have read Paul's addition (thanks Paul) to this site so that is my starting point. My YT's wiring diagram shows an "A" and a "B" terminal on the ammeter. Just which is he A and which is the B?. I can find no marking. I can of course check this with an external voltage source if need be. But is the petrol gauge polarity sensitive or not? That is really the only bit I can't sort in my mind, not knowing just what is in the gauge. Something you might all enjoy. Inspired by Anton P, I had made up the little bench to hold the dash during wiring it. (Actually having this done now by A N Other, as I am no longer able.) But in retrospect, it may be easier to wire the dash to the short loom that is then passed through the firewall, and make the connections in the engine compartment as needed, So next time, in my next incarnation I'll consider that. cheers all KGM |
| K G Mills |
| KGM You ask "My YT's wiring diagram shows an "A" and a "B" terminal on the ammeter. Just which is he A and which is the B?. I can find no marking. I can of course check this with an external voltage source if need be." Consider that the wiring diagram shows the back of the dash as if you were looking at it from the firewall ... so the A terminal will be on the same side as that shown on the wiring diagram when you flip it face down terminals up in the correct orientation for the needle. Paul |
| Paul Barrow |
| Hi Paul. Thanks for this. Once again you are a font of guidance. From my reading, the petrol gauge could be a bimetallic strip device, so no polarity effect, just Joule heating. Regards Kevin M |
| K G Mills |
| Kevin - Just had a look at a spare gauge set I have here and as per Paul, no markings but, looking at the back of the gauge in normal pos. earth situation the lh side terminal(looking at the back of the gauge) goes to battery power connected at the starter motor contactor, and the rh side terminal is connected to the voltage regulator- willy |
| William Revit |
| Hi William, thanks for the reply. it coincides with Paul's advice. regards Kevin M |
| K G Mills |
This thread was discussed between 30/10/2010 and 12/05/2025
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