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Mechman 140A Alternator for my 242

That's horrible. I've never experienced dips below 12.5 on my 100A nippondenso alt with the efan on high, ac on, headlights on and stereo blaring.
 
While I'm waiting for Mechman to respond to my latest video, can anyone see any problem with the belt installation that might support the slipping theory? I can't. Belts are 10 x 965 mm and were new when installed 6 weeks ago.

Would a 9.5 mm belt that sits slightly deeper in the V make any difference?
BTW, I can turn the engine over and over no prob by putting a socket on the alt pulley nut and wrench away.
original.jpg


original.jpg
 
In your video, I noticed that your WB02 goes hay-wire when the voltage drops. Is this caused by the voltage drop or is this a sign of a short in your system?

I'd loosen the belts back to where you had them, personally. I am running a single belt and have no slippage with more than 1/4" deflection.

Does the Voltage drops only happen when your AC and fan(s) are on?
 
Have you tried grounding the alternator's case in a better/different manner? just a quick thought.
 
In your video, I noticed that your WB02 goes hay-wire when the voltage drops. Is this caused by the voltage drop or is this a sign of a short in your system?

It's not a short. It's caused by the voltage drop, which is obviously dropping below 12v.

I'd loosen the belts back to where you had them, personally. I am running a single belt and have no slippage with more than 1/4" deflection.

I never had any slippage with any Bosch alternators or pulleys either.

Does the Voltage drop only happen when your AC and fan(s) are on?

No. That's just the easiest and fastest way to repeat it so I could get it on video. The voltage drop will also occur with no accessories on if the car is driven for awhile to get things good and hot under the hood.
Dave B
 
I would chase the exciter wire all the way back before condemning the alternator.

Try jumpering the exciter wire to Batt + and see what it does there. I had problems in the dash of my car that took me a bit of work to sort out that would randomly stop charging.
 
I would chase the exciter wire all the way back before condemning the alternator.

Try jumpering the exciter wire to Batt + and see what it does there. I had problems in the dash of my car that took me a bit of work to sort out that would randomly stop charging.

Good suggestion. I jumpered the wire direct to the battery +. Made no difference.
Dave
 
Strange indeed, I sit on 14v all the time, running a 120amp landrover alternator on the B23E in the 142s.
I do however have a chromed 200amp mustang alternator (normal form factor) to go on it because it's a stereo car.
 
and you're one hundred percent sure that you don't have a pre-existing wiring/electrical issue? You stated your 100A alternator was barely holding up, curious why you think that and don't suspect anything else...
 
Maybe the voltage regulator on it is defective? Some of the new made in China VRs are not very good. Does it use a GM VR? Or one not made in China?
 
Maybe the voltage regulator on it is defective? Some of the new made in China VRs are not very good. Does it use a GM VR? Or one not made in China?

Also check the "lock nut" on the posts on back of alt.that hold them in the hsg.
 
****. Now I'm out of thoughts.

Talk to Matt today, he should be in the office.

I sent Matt the latest video on Friday. Hopefully he'll get back to me soon. I know nothing about these GM alternators, but I cannot see any other answer except the alternator (or regulator) is defective.
Thanks,
Dave
 
Did some more tinkering today and I have some good news and hopefully not premature. I’ll get to it in a bit.

I was thinking the culprit might have been the Delta variable fan controller I am using for the primary fan. So I disconnected it and hard-wired the fan on low speed. The voltage dips continued as before.

While messing with stuff, I decided to eliminate the battery disconnect switch (see photo) from my negative post. I had been using it for a couple years. It comes in handy when working under the hood, but I thought it could be a source of resistance for the ground.
batterydisconnect.jpg


And so I think that switch was the culprit. I ran the car up to fully warm, turned on the AC w/fan on high, headlights and brights and let it idle for a good long time. The voltage dips did not return. As I mentioned, hopefully it’s not too premature sounding a victory. I’ll continue monitoring.

If this was the cure, then I guess the cause was resistance in the ground, which seemed to materialize when warmed up and/or with a moderate load.
 
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Your batt terms & cables are clean correct? Sometimes just a little corrosion makes a difference under hi load. Then I've seen some so corroroded I did not see how thay could pass current. But they did. 12V DC can act strange sometimes.
 
Your batt terms & cables are clean correct? Sometimes just a little corrosion makes a difference under hi load. Then I've seen some so corroroded I did not see how thay could pass current. But they did. 12V DC can act strange sometimes.

Clean AND new. The only older part was that disconnect switch I tossed.
 
Youve got an alt or a regulator problem...those belts need to be really loose to cause slippage, and you'd hear em squeal if they were slipping, and with a dual belt setup you definatly wont have slippage. Loosen them up so you dont tear the bearings outa that water pump, cause that will happen.

I did the ford regulator mod to my bosch 100a, and i dont have a ton of electrical in my car. The results are better than what i had with the stock regulator, even with a hot alternator. But there is still some to be desired. I noticed that below a certain RPM though the alt just wont charge, heh. What do those alt's go for $$? and whats so special bout the mechman alt?

Mark

BTW, a solution for idle may be an overdrive pully. Spin that alt faster at idle and well, it will charge better. You dont have to go much faster. What are the pully options?
 
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