My last report

[Ahsai]

Btw, I don't think reving the engine will have much effect on the voltage drop because the alt output voltage is regulated by the solid state regulator at the back of the alternator at all engine speed. I.e., your battey gauge reading does not change based on the rev either.

The exception is if your alternator is marginal and doesn't regulate the output effectively, then the ouput voltage may rise a bit when you rev up the engine.

[niceguy]

Ahsai, you are my life saver! I must thank you for every careful step in explaining what I have to do.

I want to try all of the Test C, but I cant reach the engine side of ground strap on the turbo from under the car because the engine strap bolt is located on top of the engine. Also, I cannot reach it from the engine bay because those engine oil filler tube, air pump and hoses are all in the way. Do you know how I can reach it?

Vdrop between airfilter bolt and engine side of ground strap (#36) (wish I could get to the engine side of the ground strap, I'm really gutted)Vdrop between engine side of ground strap and chassis side of ground strap (i cant reach the engine side ground strap, can I simply use the engine shell as a replacement?)Vdrop between chassis side of ground strap to chassis side of #1 (battery -ve cable) (will try that today)Vdrop between chassis side of #1 and -ve battery terminal (will definitely try this too)

Use a jumper cable to short out the -ve battery terminal (on the battery or the lead?) and the airfilter bolt and you should see immediate improvement. Try to use gauge 8 or fatter jumper cable. (will try this)

Do I have to try them with ac on and headlights just like Test A & B?

I will definitely need the luck. I am going to report back today, please wait for my good news.

Thanks also for the explanation on reving the engine vs Vdrop.

James :)

Edited June 1, 2013 by niceguy

[Ahsai]

Vdrop between airfilter bolt and engine side of ground strap (#36) (wish I could get to the engine side of the ground strap, I'm really gutted)Vdrop between engine side of ground strap and chassis side of ground strap (i cant reach the engine side ground strap, can I simply use the engine shell as a replacement?)Vdrop between chassis side of ground strap to chassis side of #1 (battery -ve cable) (will try that today)Vdrop between chassis side of #1 and -ve battery terminal (will definitely try this too)Use a jumper cable to short out the -ve battery terminal (on the battery or the lead?) and the airfilter bolt and you should see immediate improvement. Try to use gauge 8 or fatter jumper cable. (will try this) Do I have to try them with ac on and headlights just like Test A & B?

You're welcome James and I really hope you can confirm it's the ground strap before replacing it due to the labor. Sorry I forgot you have a TT. I can see both ends of my ground strap ('03 C2).

"can I simply use the engine shell as a replacement?" <- YES

"on the battery or the lead?" <- clamp it directly on the battery end of #1 without disconnecting #1 from the battery. Just make sure #1 is tightly on the -ve battery terminal.

Yes, test with ac and headlight ON just like other tests.

Good luck!

[niceguy]

Thks a lot again, Ahsai

Results

Vdrop airfilter bolt to engine case= 0.9-1.2v

Vdrop engine case to chassis side ground strap =1.5-1.6v

Vdrop chassis side ground strap to battery -VR terminal = 0.01v

Vdrop chassis side #1 to battery -be terminal = 0v

Jumper from battery -ve term to airfilter bolt did not see any improvement perhaps the jumper lead is thinner than 8 gauge.

New discovery about #36, the engine side bolt is loose because I can wiggle the ground strap around but sadly I couldn't reach the bolt to tighten it. The wires inside the ground strap appears to be brown and in rusty colour. Are the wires supposed to be silver in colour inside the ground strap?

Should I bring the car in to my Indy and him to replace #36 the r hind ground strap? Will this fix the low voltage problem for a while? Meanwhile I will order the #28 fix as well.

[JFP in PA]

Thks a lot again, AhsaiResultsVdrop airfilter bolt to engine case= 0.9-1.2vVdrop engine case to chassis side ground strap =1.5-1.6vVdrop chassis side ground strap to battery -VR terminal = 0.01vVdrop chassis side #1 to battery -be terminal = 0vJumper from battery -ve term to airfilter bolt did not see any improvement perhaps the jumper lead is thinner than 8 gauge.New discovery about #36, the engine side bolt is loose because I can wiggle the ground strap around but sadly I couldn't reach the bolt to tighten it. The wires inside the ground strap appears to be brown and in rusty colour. Are the wires supposed to be silver in colour inside the ground strap?Should I bring the car in to my Indy and him to replace #36 the r hind ground strap? Will this fix the low voltage problem for a while? Meanwhile I will order the #28 fix as well.

It sounds like the ground strap is not only loose, but is showing signs of corrosion. Time for a new one, being sure to clean off the contact point where it bolts on as well.

[niceguy]

Good newsI hv attached a 4-meter long 4-gauge ground cable, from a not so directly location at the engine ground to the chassis ground strap bolt and the voltage went up immediately. It went from idle engine 12.6v to 13.1v at the battery.

But, that 4 gauge ground became a little hot. Could this be due to the length of the 4-gauge cable being 4 meters long creating too much resistance?

Edited June 2, 2013 by niceguy

[niceguy]

Thks Ahsai n JFP :)I will ask my Indy for a new #36. Is it a gd idea to add some extra 4 gauge ground?

Did Test A show that the #28 is going to fail soon? Its Vdrop is 0.22v. What should a good one be? Should I get a new #28, too?

Finally, a big thank you to all everyone who helped! I am truly grateful for finally getting to the bottom of the low voltage problem. :)

I will report back after a new #36. :thumbup: :thumbup: :thumbup:

James

Edited June 2, 2013 by niceguy

[niceguy]

I realised the Part no. 99660703401 for the 2001 996 Turbo is what I will need. It takes 4 weeks for my local dealership to have it backorder at $60 usd.

Can I actually put THREE 4-guage cables from the original engine strap location to the original chassis engine strap location and add a few other engine to chassis straps instead of being ripped off? I have already got 4 meters worth of 4-guage cable with each side crimped with hydraulic crimping machine.

Edited June 2, 2013 by niceguy

[JFP in PA]

Can I use the engine ground stray with Part No: 99761109000 or must I stick with the old Part no. 99660703401 for the 2001 996 Turbo?

Two points: You must use the one that is correct for your car (the turbo cars run the Metzger engine which is totally different than the M96), and I would check with the dealer to make sure you get any updated part number.

[Ahsai]

All right! Glad you confirmed the culprit. Just realized I meant to ask you to use the jumper directly on the engine and not the airfilter bolt. Thats why you didn't see improvement.

Anyway, I think 0.22v vdrop on #28 is still excessive and should be addressed eventually as well.

Regarding ground strap, I think you can replace with equivalent but keep in mind that the cable is exposes to the elements so you need to make sure it is weather proof. As long as it's as fat and as short as the factory cable with equivalent crimps and heavy connectors at its ends, I think you would be fine.

Edited June 2, 2013 by Ahsai

[Loren]

The latest factory cable is much improved. I would use the latest factory part.

[Ahsai]

James,

I just did Test A on my car and what do you know, I got 0.46V with a/c and headlights on (total ~57A load). Test B I got 0.037V (i.e., very good ground strap).

My alt +ve is 13.84V (a little low), eng +ve term is 13.34V, and battery terminals are at 13.18v.

Therefore between the alt and the battery, I lost total of ~0.7v (~0.5V on what's equivalent to your #28 + ~0.2V for the rest of the cables in between). Hope that gives you a reference.

Even though I don't have any symptoms, based on the measurements above, I would want to change that #28 to the updated version some time.

Edited June 2, 2013 by Ahsai

[niceguy]

Thanks Ahsai again and thanks Loren.

My battery hasnt been receiving the correct charge for almost 3 weeks now. It is down to 10.1-10.2 during crank. Therefore, I just cant wait for 4 weeks from the dealer or have it shipped internationally from the state. It will cost $88 usd for it to reach me in a week's time. So, I plan to put FOUR 4-gauge cables together and have them crimped professionally using a hydraulic crimping machine and put some weather proofing material on top of the cable and use it that way. This time I will also make them 16-17cm long instead of 4-meter long (the cable came in one piece crimped on each side) . The question is, will THREE or even TWO 4-guage cables be enough?

[niceguy]

James, I just did Test A on my car and what do you know, I got 0.46V with a/c and headlights on (total ~57A load). Test B I got 0.037V (i.e., very good ground strap).My alt +ve is 13.84V (a little low), eng +ve term is 13.34V, and battery terminals are at 13.18v. Therefore between the alt and the battery, I lost total of ~0.7v (~0.5V on what's equivalent to your #28 + ~0.2V for the rest of the cables in between). Hope that gives you a reference. Even though I don't have any symptoms, based on the measurements above, I would want to change that #28 to the updated version some time.

Ahsai,

Thanks for sharing your results of Test A and B. I can now build a much better picture of what a basic electrical looks like in my head. You do have a very strong ground compare to mine!! :) My Vdrop is 1.45v :oops:.

In terms of my results for Test C, what do they indicate?

Vdrop airfilter bolt to engine case= 0.9-1.2v (not sure about why I lost voltage here)Vdrop engine case to chassis side ground strap =1.5-1.6v (this is the voltage I lost with #36)Vdrop chassis side ground strap to battery -VR terminal = 0.01v (not sure about this one)

Lastly, what does the result from the Toyota test of the open circuit - insulated side = 0.35v show? Toyota says it should be under 0.2v. Is there anything that I should worry about here?

Thanks for everything again, Ahsai :notworthy: :notworthy: :notworthy:

Edited June 3, 2013 by niceguy

[Ahsai]

Your test C reveals that the ground strap is bad because the airfilter bolt and the engine are separated by the ground strap. Similarly, the engine case and chassis are separated by the ground strap (obviously) hence you saw 1.x volt in both cases.

The Toyota tests were just to illustrate the principles in general. On Toyotas, the battery and the alternators are both in the engine bay so the cables are much shorter than ours so it's not surprising our cars have a little bit higher drop but now I think 0.35v sounds pretty good (especially after I measured mine :eek: ~0.7V all lost on the insulated side). So I think you can probably ignore #28 for now, which is actually good news since I can only imagine the labor for that...

I do agree with Loren and JFP that using the stock ground cable will be the best considering the labor to replace it. However, if you need a stop gap solution, as long as the "aggregated" thickness is comparable to the original ground strap, you should be fine. Heck, anything will be better than your current situation! :thumbup:

[Ahsai]

Btw, have you considered adding the cable you plan to make at a different location (somewhere on the engine case and the chassis) as a temporary extra ground strap while waiting for the OE ground strap?

[niceguy]

Hi Ahsai,

I thought about your suggestion and your are right, I will do that.

Do you know roughly the length of the #36? Because I will need to bring my 4m cable to the shop for them to professionally crimped it and put some weather protection on it. I plan to add only THREE 4-gauge cables to the existing one for now. Do you think the heat that I felt in the 4 gauge cables came from the extra length and not mainly because it is not thick enough?

[Ahsai]

Hi James, I do not know the length but my guess is it's <0.4m so the resistance will be at least 10 times less if you only use one 4 gauge cable (resistance directly proportional to length). With THREE in parallel, the resistance will be 30 times less than a single 4m 4 gauge cable. Power = I^2 x R so for the same current I, the power produced by the cable (as heat) will be 30 times less.

Edited June 3, 2013 by Ahsai

[niceguy]

Wow, you are not only kind but also knowledge. Thanks again for the info.

I will be working on the car in a few hours and hopefully report back with some gd news.

James

[niceguy]

I bought some special tools to see if I could really squeeze my small hands to reach the bolt at the ground strap at the engine side. But, sadly, no matter how hard I tried I just couldnt reach it. So, my only option now is to get my indy to do it from the engine cover tomorrow if he has time. I will report back as soon as I get it fixed.

[niceguy]

Latest report,

My indy finally had time to appoint my car. He fitted 2 wedding grade cables which have twice the amount of copper wires than the stock engine to ground cable for me. One from the engine to chassis and the other from gearbox to chassis. The problem has now been solved. Cannot be happier :)

Car now seeing close to 14v without AC and headlights, 13.5v with AC and headlights on, hopefully I can see 13.7-9v when the battery is charged from the current 11.8 to 12.6v.

Thanks every one who helped, especially to Ahsai who helped tons. :notworthy: :notworthy: :notworthy: Full respect to him, thanks again!!!

James

[Ahsai]

Glad things work out for you James and good call on fatter cables :clapping:

[Ahsai]

Niceguy, if you're still monitoring this thread, just want to let you know I just replaced my equivalent of your #28 in my car. I had about ~0.5v vdrop on that segment alone @52A. The new cable is thicker than the old one (9.1mm diameter vs 8mm), the vdrop is now only 50mV!! @ 54A load (a/c and low beam ON). It turns out my old cable is very corroded at the starter end where the two segments are joined together and covered by a rubber sleeve. You won't be able to see it until you remove the cable.

So I think the latest version of #28 should improve your 0.22v vdrop there.

Edited July 4, 2013 by Ahsai