93 ATX misses badly with electrical load

[jasonb75]

My 93 ATX runs perfectly with everything off, but as soon as I turn on the lights and HVAC system, the car begins to miss badly. If I'm idling it will miss bad enough to sometimes die. I figured maybe a ground problem, so I replaced the ground from the engine to the battery with 4 guage wire, and replaced the ground from the battery to the chassis with 8 gauge wire. I also went ahead and replaced the battery just in case.

Does anyone else have any ideas what this problem might be? Makes it kinda hard to drive at night and its my daily driver. Thanks in advance for everyones help.

 

[hawkeye18]

Sounds like a bad alternator bogging down and taking the engine with it under load.

I think you can disable the alternator by unplugging the connector from it. Then start the engine and turn the lights on.

Since I'm not sure whether disconnecting the plug will totally disable it, a sure-fire way is to simply remove the belt. Don't worry; your engine will run just fine without coolant for the minute or so it'll take you to do the test. Once you fire the engine up, turn the lights and HVAC on. Does the engine still bog and sputter? If no, simply replace the alternator (a 20 minute job, 10 if you've done it before - I can do it in 5 lol). If it does still bog, hook the belt back up and take it to an AAP or AZ and have them run a battery check (their checker will place a load on it just like your lights do) and it should tell you what's wrong.

I don't think it's the battery.

 

[SHOZ123]

Voltmeters are wonderful devices for checking alternators and batteries.

 

[hawkeye18]

Voltmeters are wonderful devices for checking alternators and batteries.

AAP has a nice hand-held battery tester unit with clamps and a switchable 400A load. I think it cost about $40 and it has been invaluable for troubleshooting charging system woes on the SHO (which are probably the most common by far), as it tests batteries in and out of the car, the starter, and the alternator all in one.

 

[zach44102]

im not a genius by no means but have you changed your wires any time soon... wen i bought my sho when he put the wires on he did them in the wrong order so i had them firing in wrong order and had similar problems.

 

[Bob Gervais]

Voltmeters are wonderful devices for checking alternators and batteries.

This is the simplest route. Check voltage at the battery with the car running, then put on the accessories and check the voltage again.