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Old 11-26-2017, 03:34 PM   #26
swedish-rocket
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Battery is probably 2 weeks old. It's charged fairly well now. No cranking issues. It did die on the highway two weeks ago and I bought a new battery to get me back home. I had the battery checked Friday and it was good but needed charged.
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Old 11-26-2017, 04:36 PM   #27
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Those drops are still too low with that much load on the alternator. If you are exceeding the rated current draw then you want to consider a more powerful alternator.

Also I have had weird things happen with the 80 amp bosch alternator. I had one that put out less voltage due to a bad diode in the warning light circuit than what the B+ terminal voltage would be. Created a problem where the dash lights were always lit dimly since the alternator was charging at slightly over 14v but the charging lamp circuit had 12v.

Check around for more voltage drops. The fuse box can get dirty terminals because it is right near the door. If your windshield ever had a leak in that area you can get corrosion in the fuse box. Also be sure the fuses are the brass and copper type and not the white metal crap. They corrode and will cause their own set of problems when they age.
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Old 11-26-2017, 05:13 PM   #28
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There is corrosion around the terminals in the fuse box. Some are the white metal fuses you talked about. I'll take a wire wheel on my dremel and clean them soon. I cleaned the terminals on the speedo and the battery terminals yesterday. I'll keep at it and keep checking. Thanks again for the info.
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Old 11-27-2017, 09:28 AM   #29
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What were the results of the voltage drop tests??!

Using a multimeter, one lead to battery positive and the other to alternator positive. I wouldn't want to see much more than 200 millivolts. Then put one lead to alternator case and one to battery ground. If you get a high reading, you have a bad connection!!! This is with engine running.
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Old 11-27-2017, 10:54 AM   #30
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I'm waiting on set of alligator clips from Amazon. I have to remove my wastegate to get to the positive terminal on the alternator. I'll report back... it was busy weekend with drag racing and family events,lol.
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Old 11-27-2017, 02:27 PM   #31
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I'm running a 100 Amp Volvo/Bosch alternator from a 92 940. No voltage or amperage issues. Before that I was running a Denso 80 amp alternator from a 91 740. Only difference noticeable between the two alternators was 13.8 volts for the 80 amp, and 14.1 volts for 100 amp.

This is on a 88 765T with plenty of space available for a large alternator. The 100 amp Denso alternator is supposedly smaller in size.
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Old 11-27-2017, 04:15 PM   #32
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I'll check those out in the future. I have two good alternators that I have a voltage drop somewhere it's looking like. The 80amp should be enough for all the standard accessories .
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Old 12-03-2017, 03:10 PM   #33
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12.25 at alternator at idle blower on alternator positive, light and radio on. 12.11 at battery.

It was both showing 14.1 @ idle and the B+ was showing the same. The car passed the charging system test at autozone.

b+ was identical to alternator output.

I cleaned terminals and fuses with wire wheel on dremel. No changes... I'll keep looking.

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Old 12-03-2017, 03:38 PM   #34
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You can get higher voltage set point regulators to bring up the system voltage. But fix the issue first. Once you get the test leads you can look around the wiring harness for voltage drops. I get the feeling you need to upgrade the grounds in various places and fix some voltage drop issues on the positive side of the electrical system. The greenbook wiring manual has a listing of the various locations of grounds in the car.
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Old 12-03-2017, 04:45 PM   #35
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I got the test leads now. I was able to measure the alternator voltage with them. Can I test with the car not running? The battery drops voltage from 12.6 to 11.8 when the accessories on.
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Old 12-19-2017, 05:01 PM   #36
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There is .2 Volt drop on the alternator to positive battery terminal with the blower, lights, heat warmer,radio and wipers on. There is less than .05V on ground terminal to the motor and alternator. There is a .05V drop to the distribution to the inside of the car on the left fender. I ordered a new positive cable and will replace the alternator positive cable and test again.

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Old 12-26-2017, 08:14 PM   #37
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To test cables you prevent the car from starting, crank , and measure max voltage drop. It's usually more of an intermittent no crank if the cables are bad, rather than a low charge. I just diagnosed a truck that was intermittent no crank with 500mv drop on both the positive and negative=way too much.

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Old 12-30-2017, 06:10 PM   #38
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The car starts right up. I changed out the power wire from the battery to starter, starter to alternator. Still dropping voltage with all accessories on. I'll have to wait till the car is cold to check the voltage drop from the positive to the alternator. It's drops .8 volts if I turn the headlights on. .5 volts if I turn blower on. .2 volts if I turn the radio on. .2 volts if I turn the seat warmers on. It dropped to 11.5 volts with everything but AC and rear defroster on. I pushed a 8ga wire from the ground terminal to the body and didn't change anything. I'll check the alternator ground again.
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Old 12-30-2017, 07:01 PM   #39
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How are the bushings and the belt? Sounds like it's slipping under load. Is the belt shiny smooth?
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Old 12-31-2017, 01:09 PM   #40
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The bushings are fine. The belts are fairly smooth. They are only a year old. I'll mark them and crank pulley to see for some reason that could be rotating. The belts should run evenly. I just checked the voltage drop from the alternator to the battery terminal with everything on. The battery voltage was at 11.7v with everything on.

.053V alternator body to negative battery terminal.
.052V positive alternator to positive battery terminal.
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Old 12-31-2017, 03:28 PM   #41
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Sure seems like things are doing well. Yet still a low voltage? How about the meter you are using? Does it have a new battery? May be a good time to verify with another voltmeter just to be sure it is accurate.
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Old 12-31-2017, 04:49 PM   #42
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Belts were definitely slipping... I have a Craftsman Multimeter, interior gauge and harbor freight meter. They read within .1volts of eachother. I tighten the belt and now it drops to 13.3 volts instead of 11.6. I put a mark on both belts and they are not even anymore before I tightened the belt.. I just ordered some new belts. The crank pulley outer section did not rotate from the center section.

I guess what I had was a loose glazed belts and a worn out positive cable to the alternator and alternator to alternator. Thanks for all your help guys. The belt probably got oil on it from the old catch can location at some point which probably didn't help.

I replaced the positive wire from the battery to the alternator which is all 4 ga now. I put in new sections of wire for the exciter and oil pressure switch. I guess new belts will be installed next weekend.
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Old 01-09-2018, 09:08 PM   #43
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So at 750 rpm my voltage is 14.0 at the battery and 13.0 loaded.
1000 rpm my voltage is 14.0 and 13.6 volts loaded at 1000 rpm.

2000plus rpm gains .2 volts more loaded and I'm seeing about a .1 volt difference at the alternator.

How does these numbers sound?
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Old 01-09-2018, 10:32 PM   #44
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How wide is the alternator belt? 11 mm belts are too narrow. Wider 11.9 mm belts are available.
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Old 01-10-2018, 09:44 AM   #45
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Quote:
Originally Posted by lummert View Post
How wide is the alternator belt? 11 mm belts are too narrow. Wider 11.9 mm belts are available.
It's a 10x920 belt by continental.

So 10mm

The widest I saw in rockauto that was specified for that application was 11.1mm. How do you usually buy them? Do you specifically ask for a certain dimension when you goto the parts store. Looks like 10mm was a fairly standard width online for the alternator belt.

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