Surging at idle/voltage surging

tcrote5516 · Nov 3rd, 2006, 05:29 PM

Having an issue with my 95. When first started, for the first 10 minutes or so, the engine surges. Idle's normal (but a little high due to being cold) and produces 13.0 volts, then sounds like it boggs down a little and produces around 15volts, it cycles through this perhaps 3-4 times every minute, for the first 10 minuets then goes back to a normal sounding idle and produces 13.0 volts. Is this a regulator issue? Its quite a change in voltage, and I dont want it to damage the ecu, or the slew of new electronics being installed. What do you all think?

golfer · Nov 3rd, 2006, 06:23 PM

First thing get your battery checked, if it's weak it will ruin an alternator

Second thing have the alternator checked, if it's faulty it will kill the battery.

Unfortunately some of the wing nuts that work at some of those parts stores , just go by ..."the machine says...". I've seen alternators show good on the first test then fail immediately on a second test.

The alternator will activate based on the battery's voltage when it drops to ~12.3 volts. When the alternator is on it will produce ~ 14.8 volts at the battery , if it's outputting more than this the regulator is gone.

tcrote5516 · Nov 4th, 2006, 04:48 PM

Well I fired her up again today, and here is what she did. Initally it was reading a perfect 13.5 to 14v, then the engine would idle up a little and the voltahe would drop to 10v it did this cycle a few times, then held a steady 10.4 ish volts. It seems as if the altternator is capable of producing current, but whatever controls it is telling it to stop. Even though the voltage is well below what it should be. What controls the output of the alternator, and where is it located, does this sound like an alternator issue itself? Or should I just start replacing cheapest (battery cables, battery, alternator to the most expensive and try to solve it that way?

golfer · Nov 4th, 2006, 08:05 PM

Quote:

Originally Posted by tcrote5516

Well I fired her up again today, and here is what she did. Initally it was reading a perfect 13.5 to 14v, then the engine would idle up a little and the voltahe would drop to 10v it did this cycle a few times, then held a steady 10.4 ish volts.

Disconnect the battery cables and measure the voltage of the battery, it should be at least 12.5 volts to 12.9 volts.

Once again , if you have a bad battery it will take out the alternater. You should have it tested.

Quote:

What controls the output of the alternator, and where is it located,

The voltage regulator controls the output of the alternater and it's located inside the alternator. It's also this same regulator that tells the alternator when to charge the battery , it does this by sensing the voltage of the battery. When the battery voltage is low the regulator senses this and engages current flow to recharge the battery.

Quote:

does this sound like an alternator issue itself?

Again , you should have the alternator checked out.

Btw... aren't you the guy that did all that welding on the frame?? If so I hope you had disconnected the battery cables when you were welding.

golfer · Nov 5th, 2006, 01:05 PM

Btw... I also noticed you have included of electronic and electrical goodies ... you may consider getting a higher output rated alternator. The original one I believe is only rated at 65 amps which is sufficient with the original equipment in the vehicle.

tcrote5516 · Nov 5th, 2006, 08:01 PM

thanks for the help. Yes I am the welding guy lol (more work then its worth to some people, but I think its gonna be a sick rig.) No i didnt allways dissconnect the battery because my ground was ALLWAYS next to my welding piece, its a non issue as long as there is nothing important between this path. Also it was doing this before I did anything so its an ongoing issue. As far as a bigger alternator, the stock is a weak 70 amp, and every alternator I hav found has been ridiclously expensive especially the "high amperage" alts. If you know of any let me know. I am gonna replace the entire charging system, battery, all cables with 4 gauge, and replace the alt. This should do it. I believe its just a bad regulator, but since i am doing so much to this truck, whats another couple of hundred bucks. Thanks again for your help!

**88pathoffroad** · Nov 6th, 2006, 01:45 AM

A 90 amp 240SX alternator from 90-96(I think) is a bolt-in. A 110 amp Quest/Villager alternator is a mods-only swap. I have the 110 amp alt and it works great. Do a search on NPORA and you'll find all the info you need.

tcrote5516 · Nov 6th, 2006, 09:01 AM

Quote:

Originally Posted by 88pathoffroad

A 90 amp 240SX alternator from 90-96(I think) is a bolt-in. A 110 amp Quest/Villager alternator is a mods-only swap. I have the 110 amp alt and it works great. Do a search on NPORA and you'll find all the info you need.

As allways, thanks! I found your write up about the quest alt very helpful.