dailo

Im on my 4th alternator now for my 1991. (2 from powermaster, 2 from motorcity reman)

Not sure why they keep going, but im using the 160amp.

Previously my charging cable would only allow 13V to reach the battery, have replaced the charging cable and fusible link with new ones attached directly to the battery.

I cant find the jump start junction block since my car was converted to right hand drive, and the blower motor is where the battery used to be. This is why I had to wire the new charging cable to the battery directly. Hope this wont cause any problems, I did in fact leave the original cable in there, i figured double cables wouldnt hurt.

The problem is the ECM (computer scan) is seeing voltage at 1 -1.5 volts lower than what the battery is getting from the alternator.

I checked the three wires from the plug in the alternator and the larger cable reads close to battery voltage whilst the two smaller ones read 1 -1.5 volts lower.

Could something be causing the ECM to think voltage is low, thus requesting the alternator to put out more voltage?

I once read that the start enable relay could have a voltage drop across it, is anyone familiar with this?

Im stumped and I dont want to keep burning alternators all help is much appreciated!

Cheers!

rodj

ECM has no control over Alt output
CS 130 alt is self regulating.
The wire to the S terminal in the 3 wire connector @ Alt senses Batt Volts and Alt adjusts output accordingly.

oldalaskaman

any chance of you posting some pictures of that right hand drive? both inside the car and the engine compartment? I've never seen a vette. converted, thanks, bob

dailo

Sure Bob, will do that in the morning.

What would cause the S terminal or the F or L to read lower than battery voltage? say one or two volts lower?

Im unable to trace where these wires go so any tips is much appreciated!

Thanks!

oldalaskaman

The absolute best advice i can give would be for you to post this in the scan and tune section of this forum. those guys are good with this type of issue.

bill mcdonald

there is a junction block on the drivers side, behind the fender, right in line with the hood latch base going down vertically. I dont know if yours would still be there, or moved to the passenger side to mirror what has been changed. I dont know of any "jump start block" on these cars.

In what time period did you go through these alternators?
I had a similar issue. I would kill the battery with the bad alternator. get a new alternator that would last about 3 days. the battery would end up with dead cells but still say 12v and put a giant load on the alt. Although I would see 18v sometimes measuring at the battery.
Lots of guys say when your alt dies to put the battery on a charger before starting it with the new alt, as it would kill the alt right away.

engle1147

If the car was an aftermarket conversion it may make it much tougher to figure out/chase whats' going on.

Still running the stock HEI ignition coil?

I've seen a few people do distributor work and leave the secondary coil ground bar out of the distributor by accident and it usually smokes the alternator in no time flat.

Ground bar: http://shop.advanceautoparts.com/web...S_667381327___

dailo

I had a distributor issue and had the distributor replaced with a new one from DUI.

It came as a complete assembly so I was unaware of the need for a secondary ground bar.

I'll have to take apart the side vent to see if the wires are still there.

I guess the only thing I need to see now is why the wires that are attached to the alternator are showing less voltage than battery

Replaced the first powermaster in March, which had been running for 8 months.
Second replacement was three weeks ago
Third replacement was yesterday.

Measured voltage while the car was running at operating temp, and alternator is putting out 14.2 at idle, battery is brand new, and the alternator is burning hot to touch.

Cheers

SunCr

Only ECM Memory is hot from the battery.

ECM ignition is via the ignition switch and that's usually the voltage drop (though remember that everything else is using this voltage too, so you have to account for that load). Anyway drop the steering column to access the switch and measure voltage on both sides (red wires); ie, the in and the out (key has to be in the Run position or you can manipulate the switch into that position. If it's lower on the output, you can cleanup the contacts with some Electrical Contact Cleaner which usually gets some of the drop back - the rest is System load. ECM operating range is about 9 to 14.5 volts and it's going to pulse the injectors based on average voltage; ie, the lower the volts, the longer the pulse width, but absent some driveability issue, there's nothing to worry about.

dailo

Is the ignition switch the same thing as the start enable relay?

Will give it a go and see..

Thanks