I hate electrical problems! In September my alternator failed. Initially I thought it was related to my stereo, but subsequent testing shows it probably was not. Just to be sure I shipped my alternator to IR Performance to have the output bumped to 150A. When I got it back I put it on the shelf until I could get the stereo improvements done...ported enclosure, wiring upgrades, new cables, etc. A couple of weeks ago I finally re-installed the alternator and found that when I start the car the system voltage drops from 12.6vdc to around 8vdc. It wasn't doing this on the stock alternator, just the normal pull-down you see with a faulty alternator. All pulleys are stock size, same as before. I checked the alternator wiring and found it all good. I removed the alternator and took it to 2 O'Reilly Auto Parts stores for testing and both said it was defective, so i shipped it back to IR Performance. They tested it and said the output was fine. Don't understand why it failed at both O'Reilly's, but that's beside the point. My biggest question is, would having the instrument cluster removed cause this charging problem? I had the cluster out so I could install my gauge pod. Don't know if this cause my problem. Any ideas?

 

Does your battery check out ok?

 

Battery is fine. It's a new Optima D-34/78. Battry voltage reads good until I start the car, even with all accessories on.

 

I had an issue with the voltage dropping from 13 to 11 and it would go back to 13.

Turned out the positive terminal cable from the battery to the fuse box was loose. I was racking my brain as all of my alternator wiring prior to finding this appeared to be ok.

I would double check those connections.

 

start engine take a multimeter to alternator and ground and get a reading from there. If it's ok, and your battery is showing less, you got some wiring issues.

 

That's the first thing I did. Battery voltage is the same at the battery and the alternator. My battery is in the drivers side storage bin and I thought the cable might be a problem, even though it's 1/0 gauge.

 

I've seen lots of problems like this with battery relocations. Not knocking your skills, but many guys just simply don't do it right, miss some basics, etc.

First off, find out if you have an alternator shop in town that can give a GOOD diagnosis of the alternator. Even something as simple as a bad diode in the alternator will do all sorts of weird things.

Also, I don't know if you have anyone else nearby with an FD that you can buy lunch for and try swapping out alternators. It's crazy easy to remove the alternator, that would be worthwhile.

At the end of the day, if the main terminal on the alternator isn't putting out squat, that sounds like a problem with the alternator. Other possibilities is making sure the alternator itself is grounded well. It grounds through the case of the alternator to the engine block. Saw a car once with a fancy painted alternator case that didn't put out a charge. Cleaned all the paint off on the attachment points, got a good metal-metal connection, and there ya go.

lDale

 

No offense taken Dale. I welcome the input.

As for my battery relocation, it was done over a year ago and has worked fine. As I said, I used 1/0 cable fused at both ends. Used Copper Seal on all ground points.

Kind of leary about the alternator swap. Would hate to damage someones alternator.

The alternator in question was media blasted to clean it and was not painted. I also added a 4ga ground between the alternator mounting bolt and one of the strut mounting bolts on the drivers side. New 8ga ground on the engine to firewall too. Copper seal on all ground points. All ground points measure <1 ohm using a precision meter.

 

I guess the voltage is what's throwing me off. Normally, with no charging, you see battery voltage of ~12vdc. When you start the car the alternator should kick that up to ~14vdc. Mine measures 8vdc with the engine running. So the alternator or something is actually sucking the voltage down. Ignition coil maybe? That's gottta be some massive current to draw the voltage down that much, I'd expect to see some smoke or something. Bad diode in the alternator would result in less than normal charge, but it shouldn't draw down the battery voltage down that much. I'm gonna go back and recheck all my connections, my battery cut-out, all my grounds, pull the battery and have it load tested.

Keep the ideas coming!

 

Well, I finally found the problem...Last week I had the alternator and the Optima battery tested. The alternator was good, just as Igor (?) said. But I found out the battery had a cell that was bad. A word of warning...I bought the Optima on ebay less than a year ago. I took it to an Optima distributor for testing/warranty and the manufacture date was 2006. ****** ebayers! So I sprung for a new Optima and re-installed the alternator. Checked all connections and grounds...thought I had it fixed. Started the car and still only 12.2v.

I had the instrument cluster removed to install a triple dash pod for my boost and other gauges. I asked several people if this would affect charging and all said no. WRONG! Turns out the wire for the "S" lead on the alternator goes through the instrument cluster and with it removed their is no +12v ignition input to the alternator, hence the alternator does not charge. Plugged in the cluster and charge voltage went to 14.6 vdc. Nearly 2 months of dickin with this and in the end it was cranial-rectal inversion. At least it wasn't a total waste though, I did find the battery was marginal at best. Better here than on the side of the road in the middle of nowhere.

Now to finish the stereo and then take it over to Bens, where the real fun starts! (FMIC, '99 Spec turbos, lite flywheel, new clutch and aluminum radiator)