2G ECU - Alternator Issue

[ryan4269]

Ok. So long story short I’ve turbocharged my 1997 4g64, for the ECU side I bought a non-eprom 95-96 gst ecu from a local for cheap. (This is temporary, I will be upgrading to a 98 Black box and get into flashing.)

A week after the install (car was driven daily) the alternator began overcharging 16-18v and eventually died. I thought it was just a coincidence since the alternator was most likely due for a replacement.

After installing a new alt it seems to work good, 13.4-14v, however the brake and battery light are still on (but dim) which indicated bad alt from before. I ignored it and continued to drive daily for a week.

And now today.. a little over a week from when I replaced the alt, the battery and brake light shut off. I go for a drive and notice the voltage dropping, (no low battery indicator on the dash) and eventually it dies. Alternator isn’t doing anything.

Fuse is good, alt pigtail connector is good. My belief now is that the 95-96 ECU is the problem. My question is if there is anyone out there who’s experienced something like this before, other 4g64 turbos?

Does the 95-96 ecu work differently with the alternator than 97+? But why was the alt fine for a whole week?

Note: weather is getting colder, battery light didn’t come on? Exhaust is very close to alt, but could it really kill it that quick? No leaks from power steering, oil, etc

 

[99dsmer4g63]

All 2g ECUs control the alternator in the same way. Use a multimeter to verify your wiring is good from the alternator to the fuse box. 97 should have a alternator relay as well. Sounds like your having symptoms of a loose or bad wiring and or bad connection.

Verify you are receiving battery voltage on the alternator sensing wires in the 4 wire plug . Do the same with the 2- 4ga white wires on the alternator stud and both the fuse box locations where the fuse is located and make sure the bolts are tight on the alternator fuse.

The only thing the ecu does is use the fr terminal and the generator g terminal which are 2 of the 4 wires in the alternator plug. The other 2 are the sensing lines, one to the headlight circuit and the other is tied to your gauges for the battery light.

How long did you let the car see 16-18v?


-Daniel

 

[ryan4269]

All 2g ECUs control the alternator in the same way. Use a multimeter to verify your wiring is good from the alternator to the fuse box. 97 should have a alternator relay as well. Sounds like your having symptoms of a loose or bad wiring and or bad connection.

Verify you are receiving battery voltage on the alternator sensing wires in the 4 wire plug . Do the same with the 2- 4ga white wires on the alternator stud and both the fuse box locations where the fuse is located and make sure the bolts are tight on the alternator fuse.

The only thing the ecu does is use the fr terminal and the generator g terminal which are 2 of the 4 wires in the alternator plug. The other 2 are the sensing lines, one to the headlight circuit and the other is tied to your gauges for the battery light.

How long did you let the car see 16-18v?


-Daniel

Car saw 16-18v for a solid 5 before traffic came to a stop. After 30 seconds or so of idling at a stop the voltage returned to 12-13 and I thought it may have fixed itself.

However couple minutes after getting moving it came back, and I then had the chance to pull over and unplug the alt pigtail and get it home.

 

[chrysler kid]

Remanned alternators for these cars are shit

Bring it in to an auto parts store to have it bench tested

Make sure the nut to the power from the back of the alternator hasnt damaged the eyelet connection to the wire, the factory nut should have a washer on it. If it doesnt have a washer it can bend the eyelet and wire and crack the eyelet

 

[steve]

My 1G had the regulator die once, since there isn't a voltage gauge I didn't notice until my headlights blew out. I stopped right away and my red top battery was venting big time. Cooked it.

 

[ryan4269]

My 1G had the regulator die once, since there isn't a voltage gauge I didn't notice until my headlights blew out. I stopped right away and my red top battery was venting big time. Cooked it.

Mine too. Got the battery replaced under warranty and installed the new alt and battery at the same time.

Can you recommend a reputable supplier to order from? I am Canadian so I don’t have the same autopart stores, and the stores that I do have don’t carry any for these cars.

I’m assuming I just got a crap alternator

 

[Sirius1995]

check your grounds, this happened to me when I forgot to hook that ground on the new alternator, and I also cleaned other ground spots from the engine bay as well

 

[steve]

Can you recommend a reputable supplier to order from? I am Canadian so I don’t have the same autopart stores, and the stores that I do have don’t carry any for these cars.

I look locally for an automotive electric rebuilder and have them repair them.

If needed I search the Junk Yards for a clean pull and take that in to get bearings and brushes. Done that for a few cars now and those were still working when the cars left my hands.

The one that failed on me was a autoparts store rebuild I got when the original alternator brushes started arcing. I learned my lesson and took the original to a local business and I think it's still back in the car. Had them replace the regulator with an OEM part on the one that fried the battery and It's sitting spare on a shelf.

Checking the grounds is also a great suggestion. Make sure the bolts are clean that mount the alternator since they are the ground part to the block and through it to the battery.

 

[Mech Addict]

I,ve recently posted on similar symptoms. For me it was brake, battery, and coolant level. Like Steve said, no volt meter, so not sure about that piece. I think mine may have been due to lots of oil leaking on it. Check my latest build update for photo. I bought a new Remy alt, and will see how that does when everything is put back together. Others have pointed toward bad alternator in connection with this symptom.

 

[ryan4269]

check your grounds, this happened to me when I forgot to hook that ground on the new alternator, and I also cleaned other ground spots from the engine bay as well

ground on the alt? are you talking about the smaller stud? I thought it was just for cable management, I have that removed cause it hangs the wires in a hotspot.. I thought it was grounded to the block?

 

[steve]

ground on the alt? are you talking about the smaller stud? I thought it was just for cable management, I have that removed cause it hangs the wires in a hotspot.. I thought it was grounded to the block?

Checking the grounds is also a great suggestion. Make sure the bolts are clean that mount the alternator since they are the ground part to the block and through it to the battery.

That short stud is for cable management. The shortest ground path is through the alternator case, mounting bracket, engine block, starter ground cable, to the battery negative. You can add an additional ground cable there but if you do it needs to be firmly bolted before you add the cable management bundle for it to serve as the low resistance ground path.