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1994 K3500 extended cab dually

the higher RPM sometimes can allow one to push more amperage. something I was always told when running dual alts that each having their own built in regulators. iirc for them to work properly they would need diode isolators. I don't recall all the details though
 
dbrannon79 said:
the higher RPM sometimes can allow one to push more amperage. something I was always told when running dual alts that each having their own built in regulators. iirc for them to work properly they would need diode isolators. I don't recall all the details though
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Hmmm..... I'm not sure that's rectifying in my brain (pun maybe intended), at least the amperage part. I doubt 2 production alternators on a dual alternator setup are capable of outputting the exact same amperage, not to mention if one fails and gets replaced with an aftermarket replacement. But more importantly, I think of amperage in this situation as being a pull, not a push, and it's just the alternators ability to feed that pull or not. If the alternator isn't big enough, then it can't satisfy the need all of the accessories in the truck are asking for and that's when you see lights dimming and such. So in my mind, the alternators are only putting out what is needed, and not forcing juice into the system beyond what is required, and so in that situation, I can't picture them fighting each other either as they would both be just sending their power into the cable.

I was going to say that I could maybe see a diode of some kind being needed, but then I believe that would counter my statement above about pull vs push, so I'm also thinking that isn't a thing. I was curious, so I just looked at the RockAuto catalog to see if it had listings for alternators in single or dual applications for a 1998 K3500, and it didn't say that. I also tried looking at a GM catalog for a 1998 K3500 and it only listed the alternators with 3 amperages, and not if it was single or dual alternator. I looked up both a 1998 and 2002 C3500HD to see if there was anything for single or dual alternators since it would be more common in that application, but unfortunately they don't even list the alternators at all for those.

I was able to grab the harness from the truck I removed the brackets from and I didn't see anything like a diode or anything in the harness - it was just a harness that plugged into the main harness and joined the plugs of the 2 alternators together. There didn't appear to be any more magic than that.

I could be wrong, and maybe I'll find I'm wrong when I go to wire these up and consult the wiring diagram in the factory service manual, but so far I don't see any evidence that makes me concerned about the alternators fighting each other in any way. I'll definitely report back if I do though.
 
I do believe that there is some sort of a signal from the alternator on a single alternator system that triggers the tachometer into thinking its reading actual engine RPMs.
The pulleys from the 6.5 alternator has to be exchanged with a store bought alternator or else the tach will read faster.
I dont know what that signal is called but I do know its in relation to the alternator.
If two alternators are running in parallel, IDK if it would be possible to get both alternators to form that wave in unison or if one would happen to form the wave offset so it would appear to the ECM as just one flat plane with no signal IDK.
I think thats what Doug was referring too in his last post and why it may be possible that a diode may be needed to isolate the one alternator from the other to avoid mixed signals.
I think maybe in order to get an accurate picture of what alternators was used on the dual alternator systems might be to go to the GM dealer and have them look up the dual alternator system for an ambulance application then maybe if there would be a difference the parts book should show.
If the GM parts department can even go back that far.
The dealer here can look up parts for my 2000 year truck and give me a part nummer but then it lists the parts as NLA.
 
MrMarty51 said:
I do believe that there is some sort of a signal from the alternator on a single alternator system that triggers the tachometer into thinking its reading actual engine RPMs.
The pulleys from the 6.5 alternator has to be exchanged with a store bought alternator or else the tach will read faster.
I dont know what that signal is called but I do know its in relation to the alternator.
If two alternators are running in parallel, IDK if it would be possible to get both alternators to form that wave in unison or if one would happen to form the wave offset so it would appear to the ECM as just one flat plane with no signal IDK.
I think thats what Doug was referring too in his last post and why it may be possible that a diode may be needed to isolate the one alternator from the other to avoid mixed signals.
I think maybe in order to get an accurate picture of what alternators was used on the dual alternator systems might be to go to the GM dealer and have them look up the dual alternator system for an ambulance application then maybe if there would be a difference the parts book should show.
If the GM parts department can even go back that far.
The dealer here can look up parts for my 2000 year truck and give me a part nummer but then it lists the parts as NLA.
Click to expand...
Yes, diesel trucks use the alternator to run the tach, so you have to have the correct pulley on the alternator so the RPMs run correctly. I bought the correct pulleys for the alternators. I could have only bought the correct pulley for the main alternator, but chose to get it for both alternators just so they matched. You only need to run the tach signal from one alternator, not both. These are the pulleys I bought:
www.ebay.com

Pulley Alternator For Delco S6 10-12-15-17Si Cs130-144 62Mm Od 24-1250 | eBay

PULLEY CLASS S6. Delco 10474364, 10498550, 1979746, 1989104. TYPE Pulley. SAVE UP TO 5%. SHAFT DIA 17.
www.ebay.com

I took the harness from the truck I got the dual alternator setup from. I don't have it in front of me, but as I recall, it had just one wire that jumped over to the second alternator, which I'm assuming was just the signal to energize that alternator, but I haven't gotten to the point of doing actual wiring yet.
 
I believe it's the L terminal on the alternator pigtail but don't quote me on that! the tach reads RPM from the pulses on the field winding as the alternator spins. having both wired as 1 would effectively send a doubled pulse signal to the tach. I would take an ohm meter and probe the terminals on both and make sure they are not tied together into one signal wire. that would send mixed signal to the tach both alternators can work together just fine being tied together otherwise, it's just you wouldn't want the signal to the tach reading coming from both at the same time. that is where the diode comes into play. if you find they are tied together, you will want to separate the signal going into the cluster but keep it together going into the ECM.
 
MrMarty51 said:
I believe thats a grand idea so I’m thinking of copying what You did there.
I found a set of these.
View attachment 96131
But I’m going to do some measuring afore I order them.
I too had been looking at hood scoops but did not want a bunch of water pouring in, or snow. Your plan with the fender skirts is an excellent alternative.
Thank You very much for posting improvements such as these fender vents.
Click to expand...
Where did you find these carbon fiber vents? I may want to use them on my Burb.
 
It might be. I also have a smaller one on-hand. I had thought about using it and also have a remote cooler to supplement just in case, but then decided to just go with the larger one and be safe. Plus, I reasoned the larger oil cooler will help take some of the load for the overall stack. And I also didn’t want to basically build the bulkheads into the core support and then have to redo it if I found I needed to go from the smaller to the larger oil cooler.
 
n8in8or said:
It might be. I also have a smaller one on-hand. I had thought about using it and also have a remote cooler to supplement just in case, but then decided to just go with the larger one and be safe. Plus, I reasoned the larger oil cooler will help take some of the load for the overall stack. And I also didn’t want to basically build the bulkheads into the core support and then have to redo it if I found I needed to go from the smaller to the larger oil cooler.
Click to expand...
I wonder if it would be a cool addition to incorporate an AN adapter fitting that has the 1/8” female NPT and install a temperature gauge into the outlet side of the oil cooler.
Could do a pre and post sending units then toggle switch them to one gauge.
I’m sure liking the fuel pressure system set up like that, despite the problems with the gloshit faulty sending units.
Last one they warranteed I also purchased a spare, just as a preventive thing knowing that as long as I have that spare unit in the glove box the current unit installed will now outlast me. 😖😹😹😹
 
I’m thinking the $12.99 laser aimed temp gun for oil cooler is more fitting.

Idk if any of you have oil temp gauges on your rigs, but I had one on a couple of mine, and there is even one on the 2002 Toyota Tacoma I have from the original owner. Never as hot as the coolant. Never anything that makes the temp raise or lower quickly. When running an oil thats as thin as atf- you an see it react from a drive, but rarely see movement while driving…
 
jrsavoie said:
My wife doesn't understand that. Lol

She sees it as money not in the bank
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Are most all wimmen like that ? ? ? ?
I have charge accounts at both parts stores, Usually about a hundred a month at one or the other of the two.
Then she starts in about the dozer, told her yeah, going to start stacking in supplies for that so it will get a total service job and the engine coolant and that alone is 20 gallons. While thats drained a tank heater is going on. Transmission lube is differential gear lube is 6 gallons, engine oil 4 gallons and sprocket drive housings 6 pints each side is also gear lube.
It’ll be several hundred dollars for fluids then there’s filters too. 😖🫣😹😹😹
 
MrMarty51 said:
Are most all wimmen like that ? ? ? ?
I have charge accounts at both parts stores, Usually about a hundred a month at one or the other of the two.
Then she starts in about the dozer, told her yeah, going to start stacking in supplies for that so it will get a total service job and the engine coolant and that alone is 20 gallons. While thats drained a tank heater is going on. Transmission lube is differential gear lube is 6 gallons, engine oil 4 gallons and sprocket drive housings 6 pints each side is also gear lube.
It’ll be several hundred dollars for fluids then there’s filters too. 😖🫣😹😹😹
Click to expand...
Might be worth lab samples?
 
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