I regently installed an external voltage regulator to control my alternator. Its the old Chrysler one that everyone uses (1986 Dodge Omni type). I bought the proper connector and hooked it up per Electromotive/Symtech instructions. The only deviation would be that I wired the regulator in near the ECU instead of near the alternator. At idle, I get a solid 15.8V at the battery. The regulator was made in China and I've read about how many people have trouble with dead regulators. So, I paid twice as much for one that was made in USA. Solid 15.8V again. To eliminate ground questions, I bolted the case directly to my battery's negative terminal. Solid 15.8V. Hook up the stock ECU to control alternator and I get 14.5V. I'm going to try running dedicated wiring right to the alternator and see if that makes a difference. Anyone had a similar experience?

Corbin
'95 ESI-T

Now with more power and fewer leaks



Humble servant of the Wiki

Is 15.8 volts a little too high then? I think I get somewhere around 14 with mine, but I also have fluctuating lights because of the idle with my cams. At idle, the foglights, taillights, interior lights, and cluster will pulse raplidly, dim-bright, dim-bright. But Im staying within 13-14.5 volts. Thats the only problem Ive had so far. Mine is bolted on the firewall where the cruise control cable junction goes.

Well, it seemed to be related to me hooking in near the ECU instead of near the alternator. I ran dedicated wiring and set up the alternator/regulator power supply with a dedicated relay/fuse right off of the battery. That got me down to a steady 14.6V.

Corbin
'95 ESI-T

Now with more power and fewer leaks



Humble servant of the Wiki

Good info Corbin. The only time I had issues with the Omni VR going near/above 15 volts was when it was on its way out.

Also, installation of the external voltage regulator triggered a battery light and ABS light. The stock ECU grounds a wire which runs to the gauge cluster to turn on the battery light. It does this when you turn the key to ON or when the power at the ECU drops 1V below the desired level or when the power at the ECU rises 1V above the desired level. The desired level depends on temperature. When the engine is running and power at the ECU is within 1V of the desired level, the ECU lets the voltage at this wire float (no connection). This wire is solid blue. It is pin 37 on the 1995, but other years will vary. If you have ABS, the solid blue wire splits off to go to the ABS ECU. When the ABS ECU detects that the wire is grounded, it turns on the ABS light and disables the ABS solenoids via a green/red stripe wire. You paid for that ABS, so you probably want it to work, right? And the battery light is a nice feature because it can warn you if your alternator belt shreds. You can kill two birds with one stone (or two lights with one circuit):



This circuit functions similarly to the stock ECU logic. If the voltage is low (12.X volts), it grounds the wire and turns on the battery light. If the voltage is high (14.X volts), it lets the wire float and turns off the battery light. When you turn the key to ON, the battery light turns on. As soon as the engine starts, the battery light turns off. The ABS ECU likes this and turns off the ABS light. Your brakes work as intended and everyone is happy. It works on my car at least. I would be curious to see if it works for others.


Corbin
'95 ESI-T

Now with more power and fewer leaks



Humble servant of the Wiki

Originally posted by Corbin
Also, installation of the external voltage regulator triggered a battery light and ABS light. The stock ECU grounds a wire which runs to the gauge cluster to turn on the battery light. It does this when you turn the key to ON or when the power at the ECU drops 1V below the desired level or when the power at the ECU rises 1V above the desired level. The desired level depends on temperature. When the engine is running and power at the ECU is within 1V of the desired level, the ECU lets the voltage at this wire float (no connection). This wire is solid blue. It is pin 37 on the 1995, but other years will vary. If you have ABS, the solid blue wire splits off to go to the ABS ECU. When the ABS ECU detects that the wire is grounded, it turns on the ABS light and disables the ABS solenoids via a green/red stripe wire. You paid for that ABS, so you probably want it to work, right? And the battery light is a nice feature because it can warn you if your alternator belt shreds. You can kill two birds with one stone (or two lights with one circuit): This circuit functions similarly to the stock ECU logic. If the voltage is low (12.X volts), it grounds the wire and turns on the battery light. If the voltage is high (14.X volts), it lets the wire float and turns off the battery light. When you turn the key to ON, the battery light turns on. As soon as the engine starts, the battery light turns off. The ABS ECU likes this and turns off the ABS light. Your brakes work as intended and everyone is happy. It works on my car at least. I would be curious to see if it works for others. Corbin '95 ESI-T Now with more power and fewer leaks Humble servant of the Wiki

Do you work for NASA? Everything you do is just amazingly well done and somewhat hard for me to understand, lol. If I can find all the electrical parts needed I will try this, as I would like my Battery light to work.

Hi Corbin,

For what it's worth, your circuit is very similar to what's inside an Omni regulator. The Omni regulator uses a larger transistor on the output stage (rated for 10A, probably a bit overkill), as well as a flyback diode (about equivalent to a 1N4002). It also uses a 6.2V Zener after running the voltage through a divider, instead of just a 14.xV Zener. Functionally, the two circuits are nearly identical, so I bet this trick would work using the Omni regulator as well.

Originally posted by VelocitaPaola
Hi Corbin, For what it's worth, your circuit is very similar to what's inside an Omni regulator. The Omni regulator uses a larger transistor on the output stage (rated for 10A, probably a bit overkill), as well as a flyback diode (about equivalent to a 1N4002). It also uses a 6.2V Zener after running the voltage through a divider, instead of just a 14.xV Zener. Functionally, the two circuits are nearly identical, so I bet this trick would work using the Omni regulator as well.

So can I use the same VR, or do I need another one???


Regards.

I have an issue (low voltage) in which I have to use an external voltage regulator.

Since you already installed it, could you tell me how to wire it?

I can't find any good diagram telling me what wires of the ECU to plug from and to the V. regulator.

Thanks in advance

Take a look here:

http://www.symtechlabs.com/support/docs/VregInstall.pdf

Thanks Paul,

I did the install this weekend, but, pardon my ignorance, how do I know if it is working properly or not??

The car started, the voltage while idle is around 12-13, but my battery light is still on.

Regards

Originally posted by gabureiru
Thanks Paul, I did the install this weekend, but, pardon my ignorance, how do I know if it is working properly or not?? The car started, the voltage while idle is around 12-13, but my battery light is still on. Regards

That doesn't sound like it's working to me. The voltage should be pretty steady, and a bit higher than that. The battery light will stay on unless you do something similar to what Corbin described above.