Wires To Alternator Help

[MarkLinRacing]

Originally Posted by cre

You should see around 13.5v to 14.4v while the engine is running; Measure it at the battery and at the alt and reference ground at both the battery and the at the chassis. A low reading at the battery but an acceptable reading at the alternator indicates a bad battery wire or fusible link.

Mark, at least add a fusible link to that wire... VERY bad idea just running it straight... you problem may only be that you need to replace the 100A fusible link as it is, but if you want to keep the added wiring add a 100A fusible link to it.


And BTW, incase some of you haven't investigated it before, clicking on the "Next Page" link on TEWD pages (like the one I posted earlier) usually brings up a page with collector illustration with pin numbering that matches the diagram AND troubleshooting tips.

Yea with the wires there I'm seeing about 14.2V, without it I only see like 12V which to me indicated a wiring issue.

I know I should've checked for fuses.. but for some reason, I don't have any memory inspecting the 100A fuse. lol I should go do that.

[cre]

The fusible link seems to be the most common cause of voltage drop across the alt to battery line... more so than the barttery wire. This is more common in earlier MKIIIs as they use a fusible link wire as opposed to the sealed fusible link used in later models... fusible link wires are more prone to degradation over time.

BTW, you can switch the wire type out for a sealed link.

[cre]

I should add that if you use the battery's negative terminal for your ground and measure a proper voltage at the alternator's output lug but the voltage at the battery is very low you needn't bother with the other wiring on the alternator, just follow the wiring from the alternator's lug to the battery.

You can also to a voltage drop test (negative test lead to the alt's lug and positive test lead to the battery's positive terminal), the reading should be very low, more than half a volt and you need to track the drop using the same methodology until you find the cause; You can do this test across just the fusible link to see if the fusible link is the culprit, but you have to pull the section it's mounted in out of the fuse box housing so I usually test the drop across the whole thing first.

[MA70-3.0GT]

Basically then, if the alternator's throwing out any charge then it should be evident across a chassis earth & the lug when the engine's running? I'm getting 11.69 & dropping with higher revs both across earth/alt. lug & across battery terminals. Everything seems to check out continuity wise with my wiring but still no charge. I'm beginning to think reg/rec failure...


Oh, another thing I noticed was after a ten minute drive the other day the casing of the alt was quite hot (if I'd really pressed my hand on hard it would've hurt). To me that says the thing's working but the charge isn't getting past the reg/rec...

[cre]

I would just pull the alternator out and take to a parts store to have it tested... Here they all do it for free and it's easy to do. That's VERY low and below the ECU's minimum from what I've been told.

[btwilson86]

I 2nd that, get it tested. Some stores can test the regulator/diodes while it's on the car, so you literally just drive there.

[SuperSpartan]

I sometimes get that issue and am curious to how can i identify and replace the fusible link, cause all the signs point to that.