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Mechman 140A Alternator for my 242

The alt in ILLINTENT's thread looks like one off a 1970 Chevy, and yours is entirely different. What's up?

You must me looking at the 105A small case alternator. That's badvlvo's. Mine is different. 140A large case. You didn't look far enough.
Dave
 
So for me the small drop in voltage looks good. What do you think? Seems better than the Bosch. I noticed a pickup in response with Eric's car at the AutoX. Revved up much better. Did you see anything like that?
 
A couple questions:

Are you measuring the voltage at the output stud on the back of the alternator, or at the battery? Are you using a handheld voltmeter? If so, where are you grounding the black lead of your voltmeter?

If you let the vehicle sit overnight, what is the resting voltage of the battery before you start the engine. This would need to be measured at the battery terminals with a handhold voltmeter.

Also, it is absolutely imperative that you run a dedicated 4 gauge positive and negative cable directly from the alternator to the terminals of the battery. The stock Volvo charge wire is too small to carry 175 amps without significant voltage drop. That unit can easily make 175 amps at full load, and could even overheat the stock charge cable.

The cold setpoint of that alternator is 15.1 volts as it was tested before it was shipped. If the highest you are seeing is 14.5 volts cold, it is likely that either a) the battery is partially discharged or in poor condition, or b) the OEM charge and ground cables have resistance in them, and are causing a slight voltage drop. That being said, your current voltage results are still well within spec for a 12 volt system.

Matt
 
whats the serial number on the alternator??

The unit we start with is an AD244. It won't do you much good to buy a stock one though, as the ear has to be machined in order for the adjusting arm to bolt up, and the housing has to be machined to clear the lower bracket.
 
The alt in ILLINTENT's thread looks like one off a 1970 Chevy, and yours is entirely different. What's up?

It's quite a bit different. It's the later case, the one introduced in the late 80's? and has dual fans. The Mechman unit has many improvements over the original GM design including a rectifier that won't melt down under large loads, improvements in the cooling and improvements in the bearing design.
 
A couple questions:

Are you measuring the voltage at the output stud on the back of the alternator, or at the battery? Are you using a handheld voltmeter? If so, where are you grounding the black lead of your voltmeter?

Measuring at the battery, off the pos and neg posts using a handheld meter. Keep in mind it is damn near impossible to get to the stud on the alternator in a 240 Turbo unless it's removed, not to mention I don't feel like getting a third degree burn from the turbo.

If you let the vehicle sit overnight, what is the resting voltage of the battery before you start the engine. This would need to be measured at the battery terminals with a handhold voltmeter.

12.7 flat voltage cold after sitting overnight. Battery is a 4 month old Optima.

Also, it is absolutely imperative that you run a dedicated 4 gauge positive and negative cable directly from the alternator to the terminals of the battery. The stock Volvo charge wire is too small to carry 175 amps without significant voltage drop. That unit can easily make 175 amps at full load, and could even overheat the stock charge cable.

4 GA positive cable already in place. For now it's grounded to the block. 4 GA ground to battery is pending.

The cold setpoint of that alternator is 15.1 volts as it was tested before it was shipped. If the highest you are seeing is 14.5 volts cold, it is likely that either a) the battery is partially discharged or in poor condition,

Not.

or b) the OEM charge and ground cables have resistance in them, and are causing a slight voltage drop. That being said, your current voltage results are still well within spec for a 12 volt system. Matt

Thanks Matt. Testing continues.....

HOTTER TESTING:

97 deg F ambient today. Car driven for about 30-40 minutes, AC blasting.

Test with AC on, fan on 3. Nothing else. Pusher/puller fans were running higher simply because they're variable and they do that when engine is warm.
13.05 to 13.10v (compare this to cold testing of 14.05v)

Measured alternator surface temps.
Top front (case): 180 deg F
Top rear (case): 200 deg F
Top rear plastic cover: 260 deg F

Not too bad. I think my 100A Bosch would likely be at around 12.5v at this alternator and ambient temperature.

So now I think I'll add the 4 GA ground to the battery and see if it changes.
Dave B.
 
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Hooked up the dedicated 4 GA ground from alternator case to battery.

Cold test at idle (no load): 14.45v. No change by adding the extra ground.

Managed to get a clamp on the B+ post on the alternator (I did get burned dammit). So direct from alternator cold is 14.48v.

Just so we're straight Matt, I'm fine with 14.45v cold. That's close to where I would run my Bosch using the adjustable regulator.
Dave B
 
Sounds like decent results in the numbers. I am looking forward to results when the alt+ to batt+ 4ga is in place.
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That all sounds good, but 12.7 volts resting voltage on an optima is low. An AGM battery (such as optima) should rest at 13.1 volts when in good condition/fully charged. 12.7 volts resting overnight would be OK on a flooded style battery, but is low for an AGM. My fully charged XS power battery can sit for a couple days and still measure 13.1 or 13.2 volts. That could be the reason for slightly lower than expected voltage.

BTW, if all you want is a higher hot charging voltage, that can be manipulated by adding resistance to the sense lead of the adapter plug we sent you. You could easily increase the base charging voltage so that your hot voltage is also higher. The only drawback to this, is that higher charging voltages put more heat into the battery. The voltage drop that occurs with higher temperatures is intentional through regulator design. The assumption is made by most auto manufacturers that as alternator temp increases, so does battery temp. (because it is also under the hood, generally speaking) Battery and alternator service life can both be extended by backing down charging voltage as temperature increases. This is why 2005 and newer GM vehicles are computer controlled. It is not uncommon for voltages to fall to 12.8 volts during cruising conditions. It drives the "big stereo" guys nuts.
 
That all sounds good, but 12.7 volts resting voltage on an optima is low. An AGM battery (such as optima) should rest at 13.1 volts when in good condition/fully charged. 12.7 volts resting overnight would be OK on a flooded style battery, but is low for an AGM. My fully charged XS power battery can sit for a couple days and still measure 13.1 or 13.2 volts. That could be the reason for slightly lower than expected voltage.

http://www.optimabatteries.com/_media/documents/specs/34_78.pdf
Specs for my Optima lists open circuit voltage at 12.8. It's a Red Top. The Yellow Tops are 13.1v.

BTW, if all you want is a higher hot charging voltage, that can be manipulated by adding resistance to the sense lead of the adapter plug we sent you. You could easily increase the base charging voltage so that your hot voltage is also higher. The only drawback to this, is that higher charging voltages put more heat into the battery. The voltage drop that occurs with higher temperatures is intentional through regulator design. The assumption is made by most auto manufacturers that as alternator temp increases, so does battery temp. (because it is also under the hood, generally speaking)

That might become useful. What amount of resistance do you think would be a good start if this becomes needed?

The thing that would really be cool would be an adjustable resistance pot or a device that varies resistance with temp increase to bring the charge up a little when hot.

Even though my alternator gets really hot from exhaust manifold radiation, my battery is at the furthest point under the hood from engine heat and probably gets no more than 20 or 30 deg above ambient. I'll check its temp next time to be sure.

Dave
 
I would like to know how it has performed in the latest round of high temperatures.

My alt has held up without issue with the H4's on high and the cooling fan working it's ass off, all while going around town at very low engine speeds.
 
Working fine for me too. Voltage does drop pretty low IF the RPM drops too low. say, under 800. But I try to maintain around 1000 RPM idle. Works great at that speed.

There is one funny glitch that began right after installing this alternator. Periodically, the voltage will abruptly dip about 2 volts for about 1 second. You only notice it at idle. Watching the volt gauge when it happens, it acts as if there is a sudden huge load, headlights dim too, but it will occur while the AC is on steady, not cycling, so it's not that.

But before I point at the alternator, I need to isolate my cooling fan controller to be sure it hasn't gone haywire. The cooling fan is the only other component that I know of that could draw that much current.
Dave
 
Problem with Mechman Alternator:
The above described voltage dips have either become more frequent or now I'm much more sensitive to them. I'm certain now that it's the alternator and not some random intermittent current draw.

It does this whenever the car is warm and idling (no load). It can be brought on more quickly when cold simply by turning on the AC or AC and headlights.

I sent Mechman an email about the issue along with two videos showing exactly what it's doing.

Here are the two vids:
It's a bit dark, but I was trying to show how the lights dim when the volt gauge drops. Again, this is at idle with AC and headlights on. You can see my A/F gauge flashing an error message whenever voltage drops below 12v.
<object width="640" height="385"><param name="movie" value="http://www.youtube.com/v/2owP5U2vAUk?fs=1&hl=en_US"></param><param name="allowFullScreen" value="true"></param><param name="allowscriptaccess" value="always"></param><embed src="http://www.youtube.com/v/2owP5U2vAUk?fs=1&hl=en_US" type="application/x-shockwave-flash" allowscriptaccess="always" allowfullscreen="true" width="640" height="385"></embed></object>

This vid shows my digital meter measuring voltage at the battery when it occurs.
<object width="640" height="385"><param name="movie" value="http://www.youtube.com/v/-uyRy4S7n8M?fs=1&hl=en_US"></param><param name="allowFullScreen" value="true"></param><param name="allowscriptaccess" value="always"></param><embed src="http://www.youtube.com/v/-uyRy4S7n8M?fs=1&hl=en_US" type="application/x-shockwave-flash" allowscriptaccess="always" allowfullscreen="true" width="640" height="385"></embed></object>
Edit: And that whine you hear going up and down (starts about halfway) is my AC fan dipping for lack of voltage.

I'd like to hear from some of you on this. I'll tell you that Mechman's response was to ask if I was running two belts (yes I am) and that the alternator belt must be slipping. They suggested that I check the belt deflection. That's a good guess and I'll get into my findings shortly.
Dave B
 
And while googling the symptoms I did find some mention of certain GM alternators that were sensitive to vibration, which was causing the regulator to reset, causing a momentary dip in voltage output. Thought I would throw this in there.
 
So at Mechman's recommendation I checked the belt deflection. The belts were tight and I could deflect them about 1/4 inch. I then tightened the belts even more, so that deflection is now less than 1/8 inch. Those belt are very, very tight. Hope I don't damage the water pump.

Here's the new video after tightening the belts. In this video, the engine has been idling for about 5 minutes. Water temp is just starting to come up. Alternator is certainly not hot in this test.
<object width="640" height="385"><param name="movie" value="http://www.youtube.com/v/V0954EStB7A?fs=1&hl=en_US"></param><param name="allowFullScreen" value="true"></param><param name="allowscriptaccess" value="always"></param><embed src="http://www.youtube.com/v/V0954EStB7A?fs=1&hl=en_US" type="application/x-shockwave-flash" allowscriptaccess="always" allowfullscreen="true" width="640" height="385"></embed></object>
 
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