Truck belongs to a good friend of mine.  A couple years ago, he had an overcharging problem.  Since the PCM (I think)  controls the charging, he wanted me to throw an external voltage regulator (EVR) on it to 'get by for awhile'..   

 

Well, it worked fine for a year or so, and now he told me yesterday that it'll peg the voltage gauge and ding the check engine chime.  the fuel gauge, he said, will often drop to empty for a few seconds, then return to normal, but doesn't seem consistent with anything else..

 

Are we at a point where he should look for another PCM?  Or has anyone seen this type of issue before?

 

Thanks, all..

 

 

Rogan

Edited August 30, 20186 yr by Rogan
Because English

Which check engine codes is he getting?

 

Has he ever checked for AC voltage coming from the alternator?

 

Absolutely check for high AC noise!

 

 

 

13 hours ago, Hawkez said:

Which check engine codes is he getting?

 

Has he ever checked for AC voltage coming from the alternator?

 

6 hours ago, sooxies said:

 

Absolutely check for high AC noise!

 

 

Mornin' fellas.  Out of curiosity, how would AC voltage cause an overcharge issue?  I totally get how it can affect signal issues for things such as TCC, and all, but to cause overcharging?  Not disputing it, just curious of the thought process as to 'why' it would..

 

  The PCM should not have any influence over the regulation of alternator voltage when an external regulator is used but the alternator voltage will have an influence over the PCM.    Maybe the external voltage regulator is going/went bad.

Actually be careful... The external regulator is sensitive to under hood temperature. If mount in an area too cold will cause it to overcharge. Then if mount to close to like the turbo the excessive heat will make it undercharge. I've had this discussion with a local tech and found an article dating back to the 1968 realm where Mopar admitted that the external regulator will change the voltage between 13.2 to 14.8 as well based on underhood temperatures. Hence why this system was ditched and the PCM controlled regulator came into existence. Now we can measure the battery temperature and regulate the voltage based on battery temperature and not under hood temperature which can swing pretty wide. 

Understood. The pcm (from a regulation standpoint) is completely out of the circuit. The evr is located by the airbox on the firewall, next to the hood hinge. I’ll get him to drop the truck off maybe next week so i can get a closer look at what’s  really going on. This megacab im swapping to a manual tcase is also his, so when it’s done I'll get his other truck. I’ll test the AC noise too, but it may just be the evr took a dump. I’d love to go back to the pcm regulation but that may require a new pcm; not 100% sure yet. 

21 minutes ago, Rogan said:

that may require a new pcm; not 100% sure yet. 

 

No it won't... We've got a solution for that too...

 

22 minutes ago, Rogan said:

I’ll test the AC noise too,

 

AC noise will need to be check and fixed but we have a solution to prevent future damage to the computers.

Or the simple version...

 

This truck is in need of a lot of catch-up care.. LOL  It leaks oil out of orifices I didn't even know it had.  So far, the running diags are as follows:

• ECM repair/replace
• AC noise check
• Rear main seal
• Front main seal
• Oil pan gasket
• Tappet cover reseal
• Full Exhaust replacement
• Clutch assembly (original has 382K miles)
• rocker adjustment
• Valve cover gasket

 

Gonna be a fun one...