Got an unknown electrical draw on the charging system. I have a brand new 120amp alternator, and had same problem before. My 95 ZJ is extremely hard to start when it's cold outside. Even after I drive it for a couple of miles, when I stop something pulls the charging system from 14 amps down to almost 9. The engine rpm drops to about 300. It will last for a short time and then it returns to 14amps and the RPMs return to normal. If it's at normal operating temp,or the air temp is moderate or higher it doesn't do this.

AC compressor is brand new Denso too. I've replaced nearly all the relays in the fuse box. Anyone had similar issue?

 

Welcome to the forum.

The 14 and 9 in the OP are volts, indicated on the dash gauge, not amps.

my initial guess is that there is not a charging problem, but instead an idle problem. If the idle drops to 300 RPM, then it is reasonable that the generator output drops, permitting the 9 volt output.

 

Any ideas on what would cause idle issue after it has been running for a couple of miles? I understand if it is cold at initial start, but not after it has warmed up some. As stated in OP, when its warm outside or the engine is fully hot in cold air temp it doesn't do this.

 

The OP's profile does not identify the vehicle or engine.

 

I did state 95 ZJ in the OP, but did not state it is a 5.2L.

Thanks

 

Has the IAC been inspected, tested and / or replaced?

Have vacuum leaks been identified and / or repaired?

 

How many heaters do you have rear window, mirrors, seats, etc. are turned on when you first start the engine.


Another thing to try first is to check and CLEAN all grounds to bare metal in engine bay along with battery cables for any corrosion inside them.


Have you had your battery load tested lately, worth a try.

 

...and then there's that battery temperature sensor in the bottom of the battery tray. Replacing that thing fixed my '99 XJ when it got wonky. Check yours out. It may have some bearing on situation.

 

I replaced the IAC and didn't fix the problem. Almost died this morning, again. It seems strange it only does this when it's cold out and only after it has been running for a few miles. The battery cables look old but not corroded and the battery is brand new. Any chance the fuel pump/regulator is bad? Seems it have problems all the time, hot or cold if that was it though. It's really hard to start in the mornings and sometimes I can hear what I think is fuel draining back into the fuel tank after I shut it off. I'll try the batter temp sensor, which seems random as hell but can't hurt since I've replaced just about every other sensor already.