Hi all, as the title says we're having issues with a low charging system voltage. Been going on for a few weeks now. Car cranks and starts OK, but gauge on dash shows well under 13V and headlights dim. Checking with multimeter at battery shows the same. In other words the dash gauge and the multimeter agree. So the dash appears to be accurate. Had the battery tested at two different places. They say it's good. 12.5 V when disconnected from the car. But voltage across the battery terminals shows 11.97V at the battery terminals with the engine running. I can put a separate charger on the battery and it does climb to ~13.5 volts at the terminals with the charger attached. I can disconnect the positive terminal when the car is running and the car keeps running. So the alternator is putting out something, but still a low voltage. We replaced the alternator, twice, no change. Occasionally when we re seated the harness connector at the alternator it would start working again and show ~13.5 volts, but then after a bit of driving it would drop down again. Thinking it was a flaky harness connector we replaced the connector. But still showing low voltage. When I started the car today the gauge crept up to just under 13V, but then slid back down.

Any ideas?

Thanks!

Bobby

Update: We just put a known good battery into the car and the issue continues to happen. We can watch the gauge go to 13V, then drop to 12.7V, then it drifts back up to 13.xV, then back down to 12.7V. Turning on the headlights causes it to drop a bit... sometimes. Other times it stays steady at whatever voltage it is.

In short it appears to be randomly drifting between battery voltage and charge voltage.

 

Reviewing your above symptoms and thinking

Have you checked for the harmonic balancer slipping? other then the belt itself from slipping

Simple test that Al has documented with a pic

There is a voltage regulator fuse that has multiple systems on it like your heated windshield washer nozzles on it of all things , bonehead engineering

And this circuit has caused problems

Hi , CDMA

 

Thanks Parker, the balancer was OK last we checked (recent), but we'll look again. It already has a stripe painted on it from that check. I'm sure I could track it down, but any hint as to where the VR fuse is located?

Thanks,

Bobby

 

It could be as simple as a loose drive belt?

 

Check the main cables for the Alternator back to the battery.

- The engine Earth strap - remove, clean and replace both ends.

- Main +ve cable from alternator to starter, and starter to bulkhead. The bulkhead connection is a known area of corrosion.


I'd suggest a Voltage Drop test between the terminals at the battery and the terminals at the alternator as an initial check..

 

I have the same problem except the headlights don't dim. I'm thinking that the gauge may be faulty in the dash. Please keep us posted if you find anything.

 

# 10 / 5 amp right engine bay fuse box

Under the fuse box and connected to the fuse box itself there are connectors if bad will limit the current to properly drive the VR without blowing the fuse

Look for the White / Blue wire

The down the line Papa Indy 61 connector the wire passes through has a history of being corroded and this also would not blow your fuse

This fuse # 10 requires that the ignition positive relay close in the corner of the right engine bay fuse box and can be swapped with the left ( only runs the horn )

 

Thank you for all the great info. The fuse and connector were good. In the end it turned out to be a loose connection at the starter solenoid. You can see in the pic that there is no compression on the lockwasher. I could move it around with a wooden stick.
.

Loose connection.

Bobby

 

Nice Pic

You can see the silver L bent battery cable terminal end to the fwd alternator

The aft cable with it's L shape terminal is facing the camera or up

That starter solenoid terminal tie point ties the alternator B + output to the rest of the battery cable through the rest of the car including the battery

13 mm socket on a 3 inch extension

 

So I surmised. I was disturbed by the terminal post in the frame near the exhaust pipes. Should that have a cover over it? Seems like a dangerous arc point. I never realized it was there.

 

Starter cable on the right wheel arc ?

I have always seen a rubber boot on it

 

How do you get a voltmeter connected to the B+ post on the back of the alternator? There is no room to get your hand back there when the engine is running. My crank pully is fine and not slipping but my alternator charge needle reads below 13 volts but not in the red. as Owner pamphlet says needle should be above 13 volts when running but not in the high side red. Could it be the alternator suppressor that is faulty? Checked engine ground and all is good also cleaned the papa indy 1 & 61 terminal blades. Any ideas?

 

Idealy the best test point is on the alternator B + post but you an go back from there and test the alternator B + battery cable at the tie in point on the starter solenoid

But .............this is not practical

Someone recently had some good pics of this tie in point and that was where his problem was

See above post 8 and 9

The next test point back would be the terminal post on the right wheel arch near the firewall

Don't use the 2 large B + terminal post on the rear firewall but you can use the smaller ground terminal post on the firewall for your meter

The down side of these test points is the integrity of the battery cable connection

The worst point to test is at the B + battery terminal post as there are 2 other tie in point connections before there

But in perfect conditions will read above a fully charge battery voltage of 12.75 to be the alternator charging voltage of between 13.5 to 14.5

You could have some corrosion in the round 2 wire connector ( there is a tab to depress to remove ) on the alternator and there is a disconnect connector for the noise suppressor about 9 inches from the alternator ( you can run the car without the noise suppressor and apparently not all X300s have a noise suppressor )

The round 2 wire connector is where your instrument cluster gets its reading and the other wire powers the voltage regulator to control the alternator give you correct output voltage

The voltage regulator inside the alternator can be changed out separately and a auto parts store can spin it up on their test machine

Part # IN435

https://store.alternatorparts.com/in...regulator.aspx

I recently had a salvage yard X300 alternator give up on the main bearing and brushes and was showing 11 volts on the instrument cluster when it was putting out correct voltage before it started noise and smoke

$ 110 dollars parts and labor local alternator rebuild shop

 

Thanks Parker 7 for the advice. Not sure what you mean by the smaller ground terminal post for my meter. I know where the left and right side firewall terminal posts are and the battery terminal post must be in the trunk near the double round fuses, right? Appreciate the help!

 

Probably pointing to the obvious but someone errored with his meter on the large B + terminal post instead of the 2 smaller ground studs on the firewall

The worst test point to test alternator output is the battery itself battery post

But bottom line it should be higher then the battery full charge state of 12.75

 

Thanks to Parker7 I think I've located the problem with my alternator. After unplugging the sound sounder the charging gauge rose up just past 13 volts like it supposed to work. The passive sounder is part LNA 2620 BA and as Parker 7 told me it's located right next to the windshield washer fill and has a black 2 wire plug. Does anyone know what the sounder does? When I plugged it back in the gauge now is charging but just over the 13 volt mark. Thanks to this forum I at least know where the problem is.

 

That is your alarm sounder speaker. You should be able to lock your car and hear that go off. If that does not happen you just found your problem

 

The sounder from my understanding is a self contained inside rechargeable battery

From reading it does go out and maybe from the charging package inside or maybe the service live of the inside batteries

It is sealed by a potting compound that may have degraded over time and water got inside from being behind the gaps in the headlights trim

Editing

But thinking on how the fuse # 10 would respond to a shorting sounder you would expect the fuse to blow before limiting current to pass through the fuse effecting your alternator output

Someone long time ago in reading brought up the notion of " counterfeit " fuses not made of the proper material or physical dimension that would behave different then the true design spec

So this points to replacing the fuse first as a cheap try before a sounder

In DCMAs case he had a shorting front windshield washer fluid nozzle heater that would blow This # 10 fuse taking out his alternator voltage regular power with it

 

Can the car operate correctly without the sounder? Is the only function of the sounder only to let you know when the locking system is activated?

 

That and the alarm going off. Someone tries to break in, which we all know are pretty hard to steal unless you have a tow truck, the alarm will not go off.