RJMcEachern

I have an 87 Trans Am GTA 5.7L Auto, gauges (no digital dash), I can't get the alternator to "turn on" and start charging. I have had the alternator tested by numerous auto electronics shops and they say it is good.

I have tested an ensured the following according to the 88 FSM (not sure if it's the same for 87):
1. Bat wire is good (0.9ohms)
2. The "S" wire is battery voltage at all times
3. The "F" wire is battery voltage with key on
4. The "L" wire is no voltage with key on

according to the 88 FSM the "F" and "L" wire work to turn on the alternator, I have determined the "L" wire is the issue and have traced it from the plug in to the bulkhead connector at the firewall (0.9ohms). There should be a 470ohm resistor in the cluster between C2 #12 and C1 #9 on the printed circuit board, but on my gauge cluster there is not one and it is evident there has never been one.



I need to know a couple of things:
1. is the 88 FSM wiring diagrams correct for an 87?
2. Why does my 87 gauge cluster not have the 470ohm resistor?
3. if I splice in a 470ohm resitor to a wire and attach the wire to the fuse panel at an ignition on 12v source then run the other end into the tan wire at C2 #12 BRN wire would this work and turn the alternator on?
4. if I do number 3 will I burn anything up?
5. Where is the bulb on an 87 gauge cluster for the battery charge light? is there one?

any help is greatly appreciated...I am at my wits end with this thing

RJMcEachern

NINÅ

RJMcEachern

Thanks NINA

I am awaiting the 87 FSM, and will report back. I have an option if I can't figure this out and that was what I was looking for.

RJMcEachern

abray1

I have had alternator problems with these cars ever since buying them. What finally made a difference was to find a local guy who rebuilds them instead of relying on autozone junk. I have him rebuild them with good parts to put out more juice especially at idle. This has proven the smartest move I have ever done. This and also to install a CS144 with the bracket adaptor. The CS144 is a better alternator. I also re-wire my battery and alternator wiring with #4 audio fine stranded wire from the alternator and #0 fine stranded from the battery which I put in the trunk. I also put a power distrubution block on the passenger fender where I get power for fans and I can also jump the car from the front or back. My lights are brighter also because of the upgrades.

RJMcEachern

My alternator was rebuilt twice now using a local service that is very trustworthy, I have used them for starters and alternators on everything from a 62 Corvair to a 2002 Corolla, with numerous other American manufacturers, and it has been tested by separate other auto electronics shops, all functional tests pass with no issues.

Thanks for the input, as stated earlier I am at my wits end so all feedback is much appreciated.

RJMcEachern

EDIT: still waiting on the FSM for 1987 Firebirds....hoping for tomorrow, but one never knows...

RJMcEachern

update:

my 87 FSM came in and the charging system diagram for the 87 Vin 8 is the same as the online 88 FSM pdf. So I am headed to Radio Crack to get a 5pk of 470ohm resistors... and solder them into the cluster...

on a different note while tuning I noticed my spark knock was up to 21 so I was looking around for noises and I noticed the water pump pulley was loose, turns out the shaft bearing is going out, replaced it and burped the system, now knock count down to 3 now @ 6degrees advance, going to burn a 8degree base timing map next...
will update soon...

RJMcEachern

RJMcEachern

so I took NINA's advice, some of the readings from the FSm and soldered in a 470ohm resistor, and wah-****ing-lah, charging at 13.6v on gauge and on DVOM...

Thanks everyone who chimed in on this post and other posts of mine with this issue... happy to have this major issue resolved

How do I marked this as solved in the title?

RJMcEachern