Hey guys,
A while back I replace my ac compressor and drier. After I did, I noticed my voltage meter was running lower. Before I could even investigate the source, my alternator went. So I figured that must've been it. I replaced my stock alternator with a 200 amp, cables from 5-90, new battery, and still when I turn on my heater and lights the voltage drops. So my next guess is a bad ground. The only ground I meddled with when installing the ac compressor was the one on the compressor itself. I triple checked it and I am still having the same issue. Also I have noticed that this electrical part (picture that isn't my battery or compressor) gets noticeably hot when just idling in the driveway. Is this normal for it to heat up like that?

 

Well, for starters, as a courtesy to other forum users, before you post pictures, shrink them to about 800 pixels wide, max, so they aren't too big to display without scrolling sideways.

Secondly, your battery clamps need to be all the way down on the posts. Start there.

Third, dropping voltage means one of two things: either you are putting an excessive load on the system, or you have insufficient conductivity somewhere.

Since you have a 200 amp alternator, assuming it's in good working condition, you aren't overloading the system.


So, you probably have insufficient conductivity. That means a wire that is too small, a connection that is not making good contact, or corrosion somewhere. This could be in the hot lead or in a the ground side of the circuit.


One more thing - before you start a lot of complicated troubleshooting, make sure of your voltage with a known good voltmeter.

But no matter what else you do, fix those battery clamps.

 

When you say your voltage drops on the voltmeter, how much is it dropping and what is the reading before you turn things on?

 

Hey Mark: Sorry about the pics, I was posting on my tablet so I just did it easy. Won't happen again. Thank you for the info, it's dark here now but I will investigate/ get those frigging clamps down tomorrow and see where that gets us for starters. Thank you again.

JooMan: It stays at about just below 12, once you hit the heater it's down to about about a white line, put on the lights and you are at about/just above the red. With a 200 Amp alternator this seems ridiculous. I believe before I did the compressor it would be pretty steady at 14.

 

Could be your gauge in the instrument cluster giving an inaccurate reading. Try comparing that to a direct reading from the batter using a multi-meter.

 

When you installed all the new wiring did you clean all the grounds down to bare metal install cable then coat with a rust preventive on all of them, this is very important. Also did you clean and tighten the starter cables including ground.


If you got lazy on any of these may very well be the cause of your continuing problems and starters are a good case for this. If you don't have one this is a good time to invest in a good multi-meter digital and a older style with a needle for some things they just work better. I have a new Fluke and a older one that I have had for many yrs. that I had recalibrated 2 yrs ago that I use.

 

I did scrape to bare metal and used Ox Gard. I put the Ox Gard between the bare metal and the copper connector. Should I coat the entire outside as well? I will double check the harder to reach ground connections (the one on the cylinder head and the B-) for cleanliness.

 

UPDATE: Ok so I got the terminals all the way down as instructed. My multimeter came today and I tested the alternator. When the jeep is off the battery reads about 12.7, when running with no accessories about 14.44, with a rear halogen light, high beams, stereo and heater running it's about 14.3- so that all seems to be checking out fine. As an XJ newb I'm pretty stoked about this.

When I turn on the accessories, the lights dim and the voltage meter in the gauge cluster still drops. Is this just a bad meter or indicative of something else?

The white piece with the two wires (3rd picture- can someone give me the proper name?) is still getting hot just idling in the driveway while I am doing my tests.

Thanks for all your input.

 

Simple fix to common Renix era Xjs...

http://www.jeepforum.com/forum/f11/r...ge-fix-684375/


And white ceramic on fender is fuel pump ballast resistor when its not warm start worrying .


Also have you done any of Cruiser54 Renix Tips ?

https://www.cherokeeforum.com/f51/cr...x-tips-153657/

 

Cool man thank you! Just wanted to make sure that ceramic wasn't gonna explode on me haha. I haven't gone through all his tips, but I will. I've replaced all the cables with 5-90 cables which he recommended, but looks like a lot of good things I can give attention to in addition to that. Thanks for your response!

 

Any time.

 

Not a bad idea, later. For protection. Right now, spend your time on solving this problem. You've done what is essential on those connections now, so you can catch up on the "nice to have" later.

Good numbers on your voltages. I'm betting on some corrosion in some wiring. When there's corrosion, voltages can read normally until the circuit is under load. Then the corroded part doesn't allow full current to flow, and voltage drops.

Try taking some measurements close to the loads (headlights, blower motor, etc.) while the load is operating. Might need an assistant for this trick.