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| Alternator Wiring | Rating: 
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| Posted: 03-16-2016 12:26 am |
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1st Post |
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Screenplay Member
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I'm cleaning up the wiring harness in the engine bay on 18341 and have a question about the three wires going to the alternator - original Lucas alternator and original wiring. There are two large gauge brown wires and one smaller brown and yellow wire that connect to the alternator. The smaller wire goes through the loom and to the pin block. One of the large brown wires also goes through the loom tape and to the battery junction. The second large brown wire sits outside the loom and and I cannot remember where it goes. The wiring diagram shows it goes to ground. Is that correct? I just don't remember it that way. Even when you think you've taken every picture you'll need, it always comes up one or two short! Thanks, Clinton
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| Posted: 03-16-2016 06:53 am |
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2nd Post |
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Jensen Healey Super Moderator 
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The ground wires are black. Brown wires are always hot. The diagram shows only one brown wire at the alternator. I'll look at the car tomorrow. Kurt
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| Posted: 03-16-2016 10:05 pm |
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3rd Post |
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Jim Ketcham Member
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Both brown wires go to the same place, the battery via the harness connector. As for why, it is a simple way of doubling the current carrying capacity between the alternator and battery.
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| Posted: 03-18-2016 02:07 am |
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4th Post |
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Screenplay Member
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Thanks for the help. After reading that the brown wires are hot, and that it goes back to the battery, I remembered that the wire met the battery positive at the starter. I'm wondering if the second wire was an afterthought as it does not appear in the wiring diagram. Would it not function, albeit less efficiently, with only the one wire as shown in the diagram?
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| Posted: 03-18-2016 01:35 pm |
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5th Post |
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Jim Ketcham Member
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I don't recall a TSB for the wire, so I would guess it was a running change. Since it cost money to add it, I would venture that it was determined that the single wire did not have adequate capacity which would cause it to get hot and be a potential fire hazard. You could replace the single with a larger wire if running two wires bothers you.
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| Posted: 03-18-2016 04:32 pm |
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6th Post |
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Tom Bradley Member
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One of the brown wires on mine came loose at one time and the alternator stopped working until I plugged it back in. So it seems to be necessary. I think the reason for the second wire is the connectors rather than the wires themselves. The resistance of even a fairly clean connector of the type on these alternators is much higher than that of the short length of wire between the alternator and the battery. When I first bought my car, it had an older, non-Lucas alternator. I had to get it rebuilt every year or two until I got smart and replaced it. So I think the guys at Jensen knew they had a reliability problem.
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| Posted: 03-18-2016 05:07 pm |
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7th Post |
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Screenplay Member
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Thank you -and good to know. I have no reason to replace or change anything regarding wiring, especially as it is not my strong suit. I only want to be certain that everything is as it should be to operate reliably. It helps immensely when the wires in your car match the Jensen diagram; all it takes is one aberration to throw me off, as I rely on that road map. Fortunately this car tracks the wiring diagram well. It is quite unlike my #19451 which follows no schematic known to man (not even the GT). I've posted questions in the past, with pics, to no avail. I've seen pictures online of late JHs with the same wires, so there is some confirmation that it is original, but I have found nothing published. Regarding the connectors themselves, I have always been very proactive about cleaning for a good contact. Are there any thoughts about dialectic grease? I've heard people swear by it - is it applied directly on the contact surface, or around the connection? I always though it was considered an insulator.
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| Posted: 03-18-2016 06:32 pm |
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8th Post |
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Tom Bradley Member
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Dielectric grease IS an insulator. What it does is keep out air and moisture to keep the metal connectors from rusting or corroding. Personally, I do not use it, but my car only drives in the San Diego area nowadays, which is a pretty benign environment. If you want to use dielectric grease, you can pretty much spread it all over: it should not interfere with the electrical connection. The nice thing about these slide-on connector is that they do a good job of pushing any contaminants out of the way, as long as they are tight. If they slide on too easily, you can tighten it up by gently squeezing the connector on the wires with a pair of pliers so the gap between the prongs and the flat section is closer together. If the connection is clean, tight and covered with dielectric grease, it should last pretty much forever no matter what the environment. Just be sure when pulling the wires off the alternator that you pull on the connector, not the wires. Copper is not that strong and you could easily end up with a frayed or broken connection.
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| Posted: 03-18-2016 10:34 pm |
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9th Post |
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Jensen Healey Super Moderator
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Hi Clinton, I finally looked and the "other" fat wire is actually black. It goes to a ground screw on the chassis.
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| Posted: 03-19-2016 11:12 am |
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10th Post |
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gmgiltd Member
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Wiring for the Lucas alternators should be as below unless Jensen in their wisdom have concocted some variation on the theme - this diagram is for the ACR alternators. The later Lucas A127 alternator is a direct replacement and is rated at 75amps, available in the UK for about £50. It's a worthwhile upgrade especially on a GT http://1.bp.blogspot.com/-6DSQglK3HfI/UK3dxzUmaOI/AAAAAAAABcI/SdgnwZ29I1I/s1600/altconn.png Gordon
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