It appears the po has bypassed the field circuit of the alternator originally controlled by the pcm. The issue is if you full field the alternator that will produce max voltage output with no regulation of charging voltage. Light bulbs and electronics do not like this. If you disconnect the relay and reconnnect the pcm if it doesn’t charge you either have a bad wire from the pcm or the pcm circuit has failed if the alternator has tested good. I am not a big fan of manufacturers moving things into pcm (voltage regulator, cruise control module, etc) because it turns a simple repair into a $800 pcm replacement.
Here is a kit to install an external voltage regulator, I have used it it works well. There is also a load resistor to prevent check engine light illumination, check the website. This kit you can put in with the overlay harness provided so no damage to factory harness.
https://store.alternatorparts.com/hd-external-voltage-regulator-conversion-kit.aspx
I appreciate the solid info..I an going to look into this another day as I am driving this jeep every day right now with no backup car. I will try to update this when I get it cleaned up.
I don’t think it’s fully bypassed - the negative circuit is still controlled by the PCM. The early TJ and YJ had the exact same alternator and the YJ used a full 12V from the ASD relay output. I don’t think there are any issues at all with the way this is wired up. Pretty sure the TJ pcm originally was providing a plain 12V and somehow that circuit got fried so they had to switch to the relay. I don’t think there is any loss of alternator control in this configuration. If this happened to the negative circuit, yes.
If it were me I’d probably remove the relay and wire it up like an older jeep, AKA run that wire to the ASD relay output and splice it and hide it in the loom.
I don’t know what year the OP wrangler is but on my 06 the pcm controls the positive side of the regulator and in this configuration a relay to bypass the field circuit would full field the alternator which will cause the alternator to charge at max output.
I see in the 98 wrangler the charge circuit looks like it is regulating the ground. So we need the year of the the TJ. If it is a early TJ that relay would just act as a charge relay.
His is a 97, so I was getting the info from that FSM. The alternator changed in I believe 2000 or 2001 to match the new engine block. They probably started controlling them differently at that point. That diagram you posted is definitely different than the early models.
So that relay is just a charge relay to turn the alternator on when the ignition is on. That circuit may of failed in the pcm. I was going off my 06 system. I would test the charging system and if functioning I would just clean up the wiring and mount the relay.
@P man You can send the pcm into us and we can run it in our Jeep for you! I apologize for the delay in responding.
Ok back in this problem now that the snow and ice are gone. I ended up buying the ERCK kit suggested previously. This is just an external voltage regulator. I installed today and everything was fine until I pulled out of my driveway and the volt gauge spiked and the check gauges light came on.
I shut it off and rechecked all connections and fired it back up no issues.
Get a mile down the road and the volt gauge pegs again.
I go home and cleaned the voltage regulator mounting points to bare metal and double checked everything. Jeep does fine driving around town running errands for a half hour.
Later today i head to the store and volt gauge pegs again!!!
I know what you are thinking: grounds. Well I have one from the VR to the alternator case and another from the VR to the battery ground.
I used the radio fuse as key on power.
All connections are new, clean and tight with proper crimps. All battery cables are clean and tight.
What would cause this spike?
I shut it off and rechecked all connections and fired it back up no issues.
Get a mile down the road and the volt gauge pegs again.
I go home and cleaned the voltage regulator mounting points to bare metal and double checked everything. Jeep does fine driving around town running errands for a half hour.
Later today i head to the store and volt gauge pegs again!!!
I know what you are thinking: grounds. Well I have one from the VR to the alternator case and another from the VR to the battery ground.
I used the radio fuse as key on power.
All connections are new, clean and tight with proper crimps. All battery cables are clean and tight.
What would cause this spike?
You did drive this Jeep as your DD for the past couple of weeks, with the PO's relay still installed. No issues then?
Generally spikes are caused by poor grounds or overcharging by the alternator likely from a failed voltage regulator, which I'm sure you know. You have addressed the grounds. This Jeep has the PCM with built in voltage regulator. Your assumption based on finding the PO's added relay was that function failed, so you added an external voltage regulator. Now getting occasional spikes. Is the PCM somehow still in the equation, perhaps the added regulator is blinding the PCM and causing it to occasionally release more voltage? I'm not an electrical expert, just tossing this out there. It seems swapping the PO's work around relay fix solution, which apparently worked, for an external voltage regulator work around fix, has caused another issue.
Possible the new voltage regulator itself is defective?
Might want to consider sending Wranglerfix the PCM for testing as well to confirm exactly what's going on with it.
Generally spikes are caused by poor grounds or overcharging by the alternator likely from a failed voltage regulator, which I'm sure you know. You have addressed the grounds. This Jeep has the PCM with built in voltage regulator. Your assumption based on finding the PO's added relay was that function failed, so you added an external voltage regulator. Now getting occasional spikes. Is the PCM somehow still in the equation, perhaps the added regulator is blinding the PCM and causing it to occasionally release more voltage? I'm not an electrical expert, just tossing this out there. It seems swapping the PO's work around relay fix solution, which apparently worked, for an external voltage regulator work around fix, has caused another issue.
Possible the new voltage regulator itself is defective?
Might want to consider sending Wranglerfix the PCM for testing as well to confirm exactly what's going on with it.
Hindsight shows me I should have just left it alone and dealt with the relay and extra wiring. Now I have made things worse.
Since the PCM is no longer connected to the alternator in any way I don't see how it could play a part in this? I appreciate the reply. I am going to pick up a meter tomorrow and check voltage at the battery when it shows the gauge spiking.
Went and bought a nice Klein tool meter this morning. Drove the jeep around for a while and luckily the volt gauge pegged while I was in a parking lot. I jumped out with my meter and checked the voltage and it's fine.
I did not install the FRM which fools the computer into thinking the alternator is still hooked up so maybe that's the issue? It is supposed to keep the check engine light off.
In hindsight I should have just left the relay and wiring alone because it worked. But I feel better now that I know my battery isn't boiling. I will keep monitoring this and let you know if any other issues appear.
I did not install the FRM which fools the computer into thinking the alternator is still hooked up so maybe that's the issue? It is supposed to keep the check engine light off.
In hindsight I should have just left the relay and wiring alone because it worked. But I feel better now that I know my battery isn't boiling. I will keep monitoring this and let you know if any other issues appear.