ECU houses the voltage regulator for 420a...?

[kergilman]

After a new alternator installation from Autozone, Battery light comes on and I flip my Apexi TT to display voltage @ 16v! Battery failed seconds later.

I tow it to a repair station at the next freeway exit and this guy is telling me my ECU might be bad...

I assumed the voltage regulator was on the alternator I replaced...but this guy is saying the voltage regulator for the 420a layout was placed in the ECU.

Can someone please verify if there any truth to this because I cannot find any information to support it and my Haynes manual is on the other side of town @ my buddies shop where I work on it.

 

[VelocitàPaola]

True, the voltage regulator is inside the ECU. If it makes you feel any better, you can get a standalone regulator from an '88 Dodge Omni for $20 rather than replace your ECU.

 

[kergilman]

Right on, thanks Paul.

So I was able to drive the poor thing home with the Apexi TT signal ground disconnected from my ECU pin 10 signal ground, which allowed the system to charge... That might throw a monkey wrench into the mix -- If I had a dirty connection to my signal ground from the TT harness, and then installed a new alt, maybe the ECU was seeing a difference in reference ground compared to chassi ground forcing the volt regulator to overcharge because it was seeing the wrong reference to true chassi ground? We also cleaned the ECU chassi ground connection for the hell of it...

If I were to have a bad regulator in the ECU, and instead of replacing the ECU installed the external one, wouldn't I then be seeing the CEL...?

And if I were to replace the ECU, shouldn't they be pretty common in the local junkyards?

 

[VelocitàPaola]

If I were to have a bad regulator in the ECU, and instead of replacing the ECU installed the external one, wouldn't I then be seeing the CEL...?

And if I were to replace the ECU, shouldn't they be pretty common in the local junkyards?

I don't know about the CEL actually... I'm fairly certain you wouldn't see a CEL as those are usually reserved for emissions related problems, and flashing CEL's are dire engine problems. The charging system has its own "CEL" so to speak: the battery light. For that, you might be out of luck as the ECU controls the battery light. Of course you could always remove the bulb from that light...

I wouldn't be so sure about ECU's being common in the junkyards. All the junkyards around here, at least, remove the ECU's before being put in the yards because they know they can be sold for a higher price. Plus, there were significant differences in the pinouts of the ECU's from year to year for 2GNT's, so you'll need to make sure you find a '99 ECU made for whatever transmission you have.

It shouldn't be an impossible task, I'm just saying it's not as easy as swinging by a junkyard and picking one up. If you post a WTB here or on 2GNT, I'm sure you'll find one in short order. Alternatively, you can buy a remanufactured ECU from Satan for about $250.

 

[kergilman]

I don't know about the CEL actually... I'm fairly certain you wouldn't see a CEL as those are usually reserved for emissions related problems, and flashing CEL's are dire engine problems. The charging system has its own "CEL" so to speak: the battery light. For that, you might be out of luck as the ECU controls the battery light. Of course you could always remove the bulb from that light...

I wouldn't be so sure about ECU's being common in the junkyards. All the junkyards around here, at least, remove the ECU's before being put in the yards because they know they can be sold for a higher price. Plus, there were significant differences in the pinouts of the ECU's from year to year for 2GNT's, so you'll need to make sure you find a '99 ECU made for whatever transmission you have.

It shouldn't be an impossible task, I'm just saying it's not as easy as swinging by a junkyard and picking one up. If you post a WTB here or on 2GNT, I'm sure you'll find one in short order. Alternatively, you can buy a remanufactured ECU from Satan for about $250.

Right on, thanks for that specific information. I was hoping 96-98 ECU's would also work, but didn't have a lot of faith in it from days of searching pin-out's to my specific 99 ECU...

I did buy an eBay Voltage Stablizer in the interm for under $20 incase I go that route: eBay Motors: HYPER STABILIZER JDM ECU MITSUBISHI ECLIPSE DSM LANCER (item 320258264082 end time Jun-02-08 17:06:41 PDT)
...but now it looks like I will be looking for a new FCD unit also. I did resolder solid connections back to my TT, but I am hitting fuel-cut constantly overheating the engine and I am afraid that I fried the FCD unit. Hahn's supplied one seemed to work well, I'll see if I can't find a comparable one and a used 99 MT ECU online...

Thanks again for the info Paul!

 

[kergilman]

I corrected my low charging issue by replacing the ECU. I found a great core-swap deal on eBay from Allcomputerresources for $199 that covers quick shipping and core return. You provide the S/N, milage, and part#...they program it and send it off. They do ECU's and PCM's. I am now charging at normal 14v!