I received and installed the voltage regulator this afternoon.

Before starting the car, I tested the battery voltage across the terminals at 11.58vDC. The car wouldn't start. So I jumped it to get it started. Then I measured the voltage across the terminals at 12.58 while the car was running.

I ran the car for 10 min, then took it for a drive around the neighborhood for 15min. After shutting down the car for 20min, it started right back up. (Then I drove it for about a half an hour to a football game).

After the game, the car started up just fine. I drove home no problem. About 2.5 hours later, car started fine again. I drove to a dinner party with my wife.

After about 3 hours at the party, the car wouldn't start again. Had to jump it to start. While driving, I noticed that the lights would dim while I was in idle, but then get brighter when I was driving.

HELP!!

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Big Fred

(RIP Sept '10) 83 300SD Turbo Diesel (aka "Rocky")
(RIP April '10 - Accident) 86 Chevy M1009 CUCV (Blazer) - 6.2L Diesel (aka "Ogre")

I assume you have made sure the belt is not slipping? If you can spin the pullley on the alterbator at all by hand (obvioulsy with the car off!) it is too loose.

A possiblity is the battery never got fully charged and started easy the first few time because it was still warm after jump starting it. Measure the voltage BEFORE you try and start it. Fully charge the battery and see if the problem persists.

If that is not it and the battery is brand new and fully charged then really the only options left are the alternator itself or wiring. Make sure the grounds are good and clean.

You can drop the alternator off the car and take it to Autozone for free testing.

If you end up needing a new alternator, I would buy a quality Bosch rebuild. Ebay is a gamble. I've purchased a 'rebuild' off there and had it quit in a couple months.

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2009 ML320 Bluetec
1985 300CD
1981 300TD

Past Mercedes
1979 300TD
1982 300TD
2000 E320 4Matic Wagon
1998 E430
1984 300SD
1980 300SD

As the other member said this does sound like something is slipping since the light is indicating it might be trying to charge and not charge at all when moving.
Oily or not tight belts and or as also stated the Alternator Pulley could be loose.

I know people deal with things differently but I would have brought my Volt Meter with me and if I thought I was having some problem I would have pulled over and checked it (you can probe the Cirgarette Lighter Socket if that works).
I also would have checked every time the Car was parked. If for no other reason that to get some more information.

You did a lot of driving but very little checking.

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84 300D, 82 Volvo 244Gl Diesel

Thanks for the help everyone.

I took the battery to Autozoo. They tested it an said "yer battery is dead". They charged it for an hour, bench checked it and then checked it in the car.

With the car running, they did a test and it showed the voltage at 13.1.

I will bring my multimeter with me and keep checking.

I does seem like the belts are loose. I cant figure out how to adjust the tension. I know how to do it on other cars, but the attachments look different.

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Big Fred

(RIP Sept '10) 83 300SD Turbo Diesel (aka "Rocky")
(RIP April '10 - Accident) 86 Chevy M1009 CUCV (Blazer) - 6.2L Diesel (aka "Ogre")

On the top of the alternator is a bolt with a tensioning screw and nut attached. Loosen the screw behind the alternator.

On the bottom of the alternator is another pivot bolt. Loosen that.

Return to the top of the alternator and tighten the tensioning nut to pull the alternator away from the water pump.


Retighten both top and bottom screws.

Looking from the front, to the 11 oclock position, I see somthing that looks like a knob, but it doesn't do anything and I don't see a screw.

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Big Fred

(RIP Sept '10) 83 300SD Turbo Diesel (aka "Rocky")
(RIP April '10 - Accident) 86 Chevy M1009 CUCV (Blazer) - 6.2L Diesel (aka "Ogre")

The 'knob' IS the screw. I belive it is a 10mm socket that fits over it. It is either 10 or 13mm. Turn it and the belt will tighten/loosen.

The tightening bolts do sometimes bend and make it hard to tighten. If one takes the alternator off they can easily bend it straight.

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2009 ML320 Bluetec
1985 300CD
1981 300TD

Past Mercedes
1979 300TD
1982 300TD
2000 E320 4Matic Wagon
1998 E430
1984 300SD
1980 300SD

Right. But be sure to have loosened the other bolts that Brian mentioned, or you'll turn the "knob" against tight bolts, and the long threaded shaft will bend. Ask me how I know...

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1984 300D: 275,000 miles (soon to be for sale)

In search of my 1987 300D in anything but white.

It does not seem to have been mentioned.

After replacing the regulator did/does the alternator idiot light illuminate when the key is first placed in the on position?

If it does slap the dash or sharply tap on the cluster near the light to see if it flickers when doing so. If it does not flicker your problem is more likely the alternator itself. If the light does flicker or go out, you need to replace the bulb. The alternator indicator light bulb is in series circuit with the alternator field coil and if the bulb's filament is burned completely out the alternator gets no field current and will not produce power correctly. If the bulb's filament is broken but still illuminates it could be making intermittent contact as it vibrates around the will not produce power correctly.

With regard to the alternator there are actually three bolts which secure it to the engine!

There are two bolts at the top, looking at the alternator head-on; there is a bolt on the right hand side sort of at 2 o’clock which has its head at the rear and a nut at the front you can see. This bolt secures the adjusting bracket to the engine/block bracket. This bolt is loosened to allow the adjusting bracket to pivot and change angle as the adjuster moves the alternator inward or outward.

The second top bolt is the adjuster sliding bolt, this bolt at the front has a threaded rod which extends leftward welded at right angle to the bolt head, the nut on the back side of this bolt is loosened to allow the adjuster tension screw/nut to apply force it moving the alternator’s upper mount to move towards or away in direction from the engine block.

The third bolt is the alternator bottom mount pivot bolt; this bolt has the nut on its front side and is easily visible from below. A very good practice is to spray all three bolts plus the adjuster screw and nut with a penetrant before starting to turn things.

All three bolts are loosened; then loosen the adjuster screw nut, you should then be able to physically move the alternator inward and outward verifying that the bottom pivot bolt rotates freely (sometimes this bolt seizes in the alternator bottom mount and fails to get loose enough on the rear bolt head end to allow the alternator to swing freely, if this happens spray it and use the method below in an attempt to free it enough to pivot), the adjuster screw nut is tightened or loosened in order to swing the alternator closer to or further from the block thereby adjusting the belt tension. The alternator needs to swing freely and pivot on the bolts to adjust and keep the adjustment setting.

If you’re simply tightening the alternator belts; that’s all that is required, if you are replacing the alternator there is a potential problem.

Sometimes the bottom pivot bolt will seize into the alternator’s bottom mount, this can usually be freed by unscrewing the bolt’s nut out to the end of the threading and with a combination of turning the bolt head at the rear and tapping the nut at the front you can get the bolt to break free. If you absolutely can’t break it free after using all the tricks of the trade i. e. heat then you will likely need to remove the engine block alternator bracket and the alternator as a whole and get it on the bench to get things free. Last resort is usually a line of holes drilled top and bottom into the alternator’s bottom bracket then using a chisel to break that bottom bracket from around the bolt. You want to do it this way so you don’t damage the engine block alternator bracket. Alternately you can grind or cut the bolt head and the bolts’s other end’s threaded section off and remove the alternator from the engine block bracket, but you’ll need a new bolt then!

As you remove the three main bolts try to keep track of the order of washers, and spacers to ensure the alternator gets reinstalled properly in the same plane of the other pulleys. Lather the bottom pivot bolt with something like Permatex Never-Seize when you reassemble to prevent problems in the future. This bottom pivot bolt is more exposed to the elements like salt and water from below and is usually more problematic, particularly if you’re in the rust belt. The top pivot bolt which secures the adjuster bracket to the engine block bracket also has a spacer that encloses that bolt, it usually does not seize but why take a chance! Good luck!

Also, check your engine-chassis ground (near the starter) and battery-chassis ground. These can cause a failure/intermittent to charge as well.

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Sam

84 300SD 350K+ miles ( Blue Belle )

Agreed.

However, I have never needed to loosen this bolt to perform the adjustment. The leverage generated by the adjustment screw is more than sufficient to overcome any friction generated at the point of contact for this bolt. The rotation of the bracket appears to be minimal in the course of a normal adjustment.

YMMV.

I see this bolt.

I don't see this bolt. Especially the threaded rod part. All I see is about a 1 inch long knob like thing that is pointing to 11 oclock and seems to be part of the alternator bracket. Based on your description, is it something like this

I don't have anything like this. So this is probably the problem. Where does the threaded part of the main bolt attach to?

I see this one.


I will have to check the idiot light the next time I start the car.

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Big Fred

(RIP Sept '10) 83 300SD Turbo Diesel (aka "Rocky")
(RIP April '10 - Accident) 86 Chevy M1009 CUCV (Blazer) - 6.2L Diesel (aka "Ogre")

I think you're seeing the one you mention you can't find, it's just that real long nut that you refer to as the knob. It is the adjuster, an "L" bolt.

Attached Thumbnails

 

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83 SD

84 CD

Yes the picture you have provided is the adjuster bolt, the main thicker bolt has its head at the front and its threaded section secured with a nut at the rear. The smaller diameter threaded rod extends from the head toward the left and has a long hexagonal nut threaded onto it.

There is a small chance that your original adjuster mechanism has been changed out for an earlier type adjuster perhaps. The early type adjuster uses a bolt with a gear welded behind its head, this gear meshes with a line of gear teeth welded onto the adjuster itself. If this sounds like what you see on your car it works basically the same, loosen everything, then the tension is adjusted by turning the gear head bolt, when turned its gear will move along the toothed track on the adjuster bracket. When you turn that bolt to the point the alternator belts are tight secure the nut on the back side of the adjuster bolt locking things in place, tighten the other bolts and your good to go.

Nope, no older mechanism. Looks like it was just removed. I see the adjuster shown in toomanybenz's pick, but there is no threaded rod extending down.

billybob, does the thicker bolt part attach to something at the back of the alternator?

Is there any work around for the bolt (that thing is $50+)?

Is the older adjuster better? How difficult is the changeover?

__________________
Big Fred

(RIP Sept '10) 83 300SD Turbo Diesel (aka "Rocky")
(RIP April '10 - Accident) 86 Chevy M1009 CUCV (Blazer) - 6.2L Diesel (aka "Ogre")