I'm retired, so I'm always interested in reading articles/posts that will increase my knowledge, provided the info is accurate. Sometimes I feel like a monkey doing math in Greek, when I read technical articles (especially when it comes to electrical...I can read a schematic, thanks to my Dad, but he never delved into theory with me); other times I'm just a lost Easter egg.
Ammeter to Voltmeter...who does it?
- Thread starter billytuffnuts
- Start date
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I'm retired, so I'm always interested in reading articles/posts that will increase my knowledge, provided the info is accurate. Sometimes I feel like a monkey doing math in Greek, when I read technical articles (especially when it comes to electrical...I can read a schematic, thanks to my Dad, but he never delved into theory with me); other times I'm just a lost Easter egg.
I meant to answer this part too. Although its more of guess than an answer. There's a couple of different types of regulators, and I suppose on an alternator with drasticly different field circuit demand, a matching regulator would be needed.
Voltage is regulated by controlling the power to the field. Field is shorthand for the coiled windings that create an electromagnetic field when electricity goes through them.
Power through the field windings can be regulated either on the wire feeding in, or the wire out to ground.
Chrysler's mechanical regulators were on the feed wire. The field return was grounded to the housing.
Chrysler's electronic regulators control flow through the wire out. System voltage is monitored by a connection to the wire in.
These two strategies go by a few different names such as, a and b circuits, or pos and neg regulation.
BCJohnny had some pertty helpful technical info and explanations in this thread: How Alternators are "Upgraded" - Speed Talk
Ah yes, the ground controlled electronic regulators. I replace the point type on my 66 with a new and improved electronic unit. Through a couple of loose mount screws to the firewall, the new regulator caused a overcharge, boiled the battery and blew out some bulbs when the lights were turned on. Yep, 18 volts is too much.
When I started taking the motorhome apart two years ago, I made sure to keep all of the parts I took off. When I reinstalled the engine, I converted over to a dual pulley setup, because I used a Mopar A/C compressor from a 1983 B150. I also took the alternator and the rest of the dual pulleys from it. I did keep the alternator I pulled off of my motorhome though, and it sat on the parts shelf. It was filthy and I figured it was probably a reman'd unit.
Today, after having thought about this thread, I decided to clean the alternator, to see if I could find a part number or date code. Lo and behold, there is the blue-anodized round aluminum tag, still on the alternator, staring right at me. 3755407, 20th week of 1975 (May 12-16), 60A...it's the original alternator.
Needless to say, it's getting rebuilt and the dual pulley is being added to it.
So my final question for you Mopar electrical gurus, because I don't want to overstay my welcome....should a 60A alternator be enough to power my motorhome necessities?
Today, after having thought about this thread, I decided to clean the alternator, to see if I could find a part number or date code. Lo and behold, there is the blue-anodized round aluminum tag, still on the alternator, staring right at me. 3755407, 20th week of 1975 (May 12-16), 60A...it's the original alternator.
Needless to say, it's getting rebuilt and the dual pulley is being added to it.
So my final question for you Mopar electrical gurus, because I don't want to overstay my welcome....should a 60A alternator be enough to power my motorhome necessities?
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67Dart273
Well-Known Member
^^Almost impossible to answer without knowing what all it's feeding. Such as keeping charged accessory motorhome batteries and other equipment in the home. THE PROBLEM is with the bulkhead connector/ ammeter. That is why the MAD electrical bypass came to be. And it doesn't take much, say 60 amp plus, where you should upgrade the alternator-to-battery charge wire.
If I had a motorhome, I'd want a BIG alternator, 100-120 minimum
If I had a motorhome, I'd want a BIG alternator, 100-120 minimum
Point taken, thanks. I can't wait to start taking long trips with it.
BTW, where are you at in Idaho? I'm in Nampa.
From everything you posted earlier, it sound like it works like this.
When parked, the coach batteries supply the motorhome. There's no connection to the engine and cab electric.
When the engine is running, the alternator recharges the battery. The alternator is wired the main charging circuit at the battery. That's probably why the ammeter showed 25 amps charging.
So the question is what equipment attached to the coach batteries would be running while the engine is running? Additionally, is that equipment regulated to 12.5 volts or will it see the system voltage from the alternator.
Your existing wiring looks like 8 ga or heavier. Routing it more directly as you illustrated maks it less likely to damage the connectors and ammeter, but still could cook the batteries. An alternator that produces more power at idle will keep the batteries from getting drained if the engine is running. But it will also be able to send more current to a completely drained battery.
As far as monitoring the charge to the coach batteries, Aircraft Spruce, Jamestown Supply and other places have remote shunt ammeters.
Correct.
Yes, the alternator charges the chassis cab battery and a wire runs from the chassis cab battery to the 12v switched battery isolator solenoid, which allows the coach/house batteries to be charged, but only when the engine is running.
Everything in the coach uses 12V, water pump, lights, heater fan and stove exhaust fan. The fridge is 3-way; 110V/12V/Propane. Ideally, you want the fridge running on 12V, when you're traveling. There have been reported instances of people running their fridges on propane, pulling into gas stations, and the flame heating the ammonia fridge ignites gasoline vapors around the pump. The only thing I can really see running on 12V, while we're traveling, would be the fridge and maybe the LED ceiling lights, if the wife needs to use the bathroom or make us a sandwich.
I had to refer to my Service Manual, to refresh my memory. The red positive battery wire to the starter relay is 6ga.; the red positive battery wire to the fusible link is 10ga.; the black negative wire to the engine ground is 4ga.; the black negative wire to the firewall body ground is 10ga.; the black alternator wire to the bulkhead connector is 10ga.; the red fusible link to the bulkhead connector is 14ga.
And sending more current to completely drained batteries is what will cook them, correct? If this is the case, what I would need is some way to shut the flow of the current to the coach/house batteries off, when they are charged, and then open the flow of current, when the batteries fall below a certain voltage.
The Power Distribution Center has an ammeter, allowing me to monitor the charging of the coach/house batteries.
If I ran a 8ga. wire, along with a 12 gauge fusible link, from my alternator output stud to my starter relay stud, this should make bypassing the bulkhead connector no longer necessary, right? If I've correctly understood everything you guys have schooled me on, since electricity follows the path of least resistance, the 8ga. wire will act as a shunt and eliminate the heavy load on the factory wiring, correct?
Yes. If you run a charging wire to either the solenoid, the relay or battery post, all power for charging will be diverted from the bulkhead connection and dashboard ammeter. You may still see some flow on the ammeter during start, because that might be be the shortest path from battery to ignition switch. 5 amps at most, less if some goes the other way.
It could be the insulation - in the photo the alternator output wire bulkhead to looked heavier than the battery feed.
My question about the regulated power supply for coach was for calculated current loads. I don't know about a fridge. For lights, if a bulb is rated at 12.8 Volts and is given power at 14.2 Volts, more current will flow through it. So if adding upo current loads, something to keep in mind.
This circles back to your question about the alternator and whether the original blue tag one will do the job. And yes, once the direct charging wire is added, the my question is whether the 60 amp has an advantage because it is self limiting. In other words the recharging rate will be 50 amps or less even driving on the highway. Lets assume 55 amps at 14.2 V, less whatever starter battery needs to get recharged, less equipment needs (5 amps for field and ignition minimum).
Now lets say a '100 amp' alternator can put out out 90 amps at 14.2 Volts while driving 35 mph or faster. That would let the coach batteries draw as mcuh 85 amps when they start to recharge (assuming they were very drained).
Might see what battery manufacturers recommend. These may be deep cycle batteries which might be OK with it. This isn't that different of a situation than boats with cabins, or airstream and other rvs.
It could be the insulation - in the photo the alternator output wire bulkhead to looked heavier than the battery feed.
My question about the regulated power supply for coach was for calculated current loads. I don't know about a fridge. For lights, if a bulb is rated at 12.8 Volts and is given power at 14.2 Volts, more current will flow through it. So if adding upo current loads, something to keep in mind.
This circles back to your question about the alternator and whether the original blue tag one will do the job. And yes, once the direct charging wire is added, the my question is whether the 60 amp has an advantage because it is self limiting. In other words the recharging rate will be 50 amps or less even driving on the highway. Lets assume 55 amps at 14.2 V, less whatever starter battery needs to get recharged, less equipment needs (5 amps for field and ignition minimum).
Now lets say a '100 amp' alternator can put out out 90 amps at 14.2 Volts while driving 35 mph or faster. That would let the coach batteries draw as mcuh 85 amps when they start to recharge (assuming they were very drained).
Might see what battery manufacturers recommend. These may be deep cycle batteries which might be OK with it. This isn't that different of a situation than boats with cabins, or airstream and other rvs.
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Good to know I can follow what you guys have been saying and learn from it.
You could very well be correct. The Service Manual is very sporadic about the MB300 chassis cab...it was primarily written for the regular B-vans. Since it makes no mention of the 100A voltage regulator that's in my rig, it stands to reason that the wiring might be a bit more heavy duty as well, which means that the wiring schematic isn't complete for my model.
At 12V, the Dometic RM66 fridge ammonia heater uses 11A; the 110V side uses only 1.4A.
The Interstate Battery guys near me are pretty savvy about what deep cycle batteries need. I'll talk to them, as well as the alternator rebuild shop down the road. I found this diagram in my Dometic refrigerator manual. Adding a relay sounds like a great idea.
Turns out you were right, the black alternator wire is indeed 8ga. I just measured it and the outer diameter is 0.213"
I replaced the amp gauge and did the bypass, then installed a new disassembled sunpro volt gauge in the cluster... Wired it to the fuse block for positive and the other wire to a ground bolt.
It worked fine for a couple days and then hit 18volts maxxed out and will not move. My volt meter says 14.5 running and 12.5 key off.
Okay, bad gauge. Ordered a Bosch replacement, looks almost identical to sunpro. Installed that making sure not to ground anything out to the cluster.
Before buttoning up the install, attached the cluster and tested the gauge. Read 12 v in accessory, and 12v IGN on. Ok, it works. Go have a beer, come back and test it one more time before tightening up the screws and steering column bolts...
Nothing. Kaput. Removed gauge and tested it in the battery with two jumper wires. Nothing.
I have two dead volt gauges. One stuck at 18v and the other at 8v. Great.
3rd time's a charm or should I give up and smash everything?
It worked fine for a couple days and then hit 18volts maxxed out and will not move. My volt meter says 14.5 running and 12.5 key off.
Okay, bad gauge. Ordered a Bosch replacement, looks almost identical to sunpro. Installed that making sure not to ground anything out to the cluster.
Before buttoning up the install, attached the cluster and tested the gauge. Read 12 v in accessory, and 12v IGN on. Ok, it works. Go have a beer, come back and test it one more time before tightening up the screws and steering column bolts...
Nothing. Kaput. Removed gauge and tested it in the battery with two jumper wires. Nothing.
I have two dead volt gauges. One stuck at 18v and the other at 8v. Great.
3rd time's a charm or should I give up and smash everything?
67Dart273
Well-Known Member
Less than that. Voltmeters draw a fraction of an amp. "the better the meter" the less they draw Something like 1/8---1/4A fuse would be oodles. I'd just put in whatever you can find locally that will protect the wiring. 1A, etc
Thank you, I'll try a 1amp fuse this time. Ordered another gauge, but trying to figure out how I'm killing them. Would a weak ground kill a volt gauge? I used the same nut that a little ground strap connects to under the steering column. I thought these volt gauges were pretty simple and foolproof?
I barely drove it, but it held steady for a day. Then parked itself at 12v instead of all the way left. The next day it was reading max 18v, but I checked with my voltmeter and it was 14.5 running. Then it parked at 18v. after awhile it just stayed at 18v and that's it.
The 2nd gauge (Bosch), worked fine when I tested it twice. Tested it a third time and wouldn't move from 8v. Not even a wiggle. Didn't even drive the car or start it.
The 2nd gauge (Bosch), worked fine when I tested it twice. Tested it a third time and wouldn't move from 8v. Not even a wiggle. Didn't even drive the car or start it.
Bronze Barracuda
Well-Known Member
Hello how did you tear the sunpro gauge to pieces? does the face just pop off? I got one in the mail today. eager to start this mod. Thanks.
Bronze Barracuda
Well-Known Member
moparmat2000
Well-Known Member
Heres what it should look like installed to ammeter face. I clipped the plastic needle leaving a short stub and super glued the ammeter needle on. I am going to run a denso alternator with a fault light so I modded mine for a red fault light. Pic 2 you remove the red shaded area so the needle can swing.
Pic 3 shows 2 wires coming out of the back of the panel. The red jumper feeds the volt gage off the 12v gage feed. I ended up eliminating the black wire and ran the volt gage ground lug right to the metal gage housing. I shimmed both gage studs to get the right height. On the negative stud I used steel washers, and sanded the gage housing to bare metal in that spot to help a ground.
On the positive stud side, I enlarged the gage housing hole and used a plastic grommet from the sun gage mounting hardware to insulate it, and stacked up plastic washers on both inside and outside of the gage housing on the positive stud to insulate it from shorting to ground.
The pot on the back you can fine tune we here you want the needle to sit at 13.5V. I set mine slightly above half on the gage.
Take your ammeter feed wires and bolt them together and cover them with either tape, or shrink tubing and shove em back into the harness. I used 2 layers of shrink tubing on mine
I hope this helps you with what you need to do
Pic 3 shows 2 wires coming out of the back of the panel. The red jumper feeds the volt gage off the 12v gage feed. I ended up eliminating the black wire and ran the volt gage ground lug right to the metal gage housing. I shimmed both gage studs to get the right height. On the negative stud I used steel washers, and sanded the gage housing to bare metal in that spot to help a ground.
On the positive stud side, I enlarged the gage housing hole and used a plastic grommet from the sun gage mounting hardware to insulate it, and stacked up plastic washers on both inside and outside of the gage housing on the positive stud to insulate it from shorting to ground.
The pot on the back you can fine tune we here you want the needle to sit at 13.5V. I set mine slightly above half on the gage.
Take your ammeter feed wires and bolt them together and cover them with either tape, or shrink tubing and shove em back into the harness. I used 2 layers of shrink tubing on mine
I hope this helps you with what you need to do
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Bronze Barracuda
Well-Known Member
Yep, definitely a big help. I like the idea of using jumper wire to feed wire. I had just test fit mine into stud holes when I noticed the center housing for the gauge wire housing clip was preventing the voltmeter from swinging properly. So just grind it away? (the shaded area). Maybe I'll wrap the cut away area with some white electric tape, (I am thinking there may be light loss through bleeding out of the cut away area)? Also, curious so a very simple way to do the MAD ammeter bypass is to just disconnect the ammeter and fuse the two wires (RED/BLACK) together either by bolting, soldering etc.
then stuff them back into the harness (Obviously shrink tube/insulate them) Nice!
Obviously these two mods would go hand in hand.
PS nice work on the red warning light from the alternator as well. Redundancy and safety also go hand in hand.
moparmat2000
Well-Known Member
If a rally dash cluster, draw a clocking line on the back of the gas gage face to the gage housing so you can line it up putting it back together. Usingg a miniature set of wire cutters (dykes) carefully pry the crimps holding the gage face to the housing and remove the face. You will be staring at pic #1 carefully dewire the points regulator inside the gas gage and leave the 12V feed stud intact on the back and make a solid state IVR. Will cost about $7 in electronics store parts. That 12V feed stud provides a 12V feed to the new external IVR and a 12V feed to your volt gage.
Also no light will bleed thru the cut out. I put aluminum tape over the hole to keep dust out. I also used flexible and dimmable 5630 LED light strip to line the gage housing. You could replace the illumination bulbs with hi bright LEDs and get the same or similar look. The strip light is peel n stick, and I ran the wires to a bulb socket. Available at evilbay in many colors. Super inexpensive.Typically about $6-$8 per 5 meters lol. That's like 13 feet.
The ammeter bypass is more than just connecting the 2 wires together. However the rest of that mod is done at the engine side of the firewall since it bypasses alternator output to the battery and (bypasses the bulkhead connector). Last pic is the bypass. One above it is unbypassed.
Take your circuit boards and solder the wiring harness pins pins to the copper tracings on the board, then take small brass brads, cut them short to fit down inside the circuit board pins allowing the pin head to overlap the back of the pin where its crimped. Either JB weld them in or solder them in to prevent to pin from loosening and pulling out.
This should just about fix everything that's fucked about the rallye dash cluster.
Hope this helps
Matt
Also no light will bleed thru the cut out. I put aluminum tape over the hole to keep dust out. I also used flexible and dimmable 5630 LED light strip to line the gage housing. You could replace the illumination bulbs with hi bright LEDs and get the same or similar look. The strip light is peel n stick, and I ran the wires to a bulb socket. Available at evilbay in many colors. Super inexpensive.Typically about $6-$8 per 5 meters lol. That's like 13 feet.
The ammeter bypass is more than just connecting the 2 wires together. However the rest of that mod is done at the engine side of the firewall since it bypasses alternator output to the battery and (bypasses the bulkhead connector). Last pic is the bypass. One above it is unbypassed.
Take your circuit boards and solder the wiring harness pins pins to the copper tracings on the board, then take small brass brads, cut them short to fit down inside the circuit board pins allowing the pin head to overlap the back of the pin where its crimped. Either JB weld them in or solder them in to prevent to pin from loosening and pulling out.
This should just about fix everything that's fucked about the rallye dash cluster.
Hope this helps
Matt
Bronze Barracuda
Well-Known Member
That looks real nice.
That solid state sure is tiny compared to the stock IVR.
Sure as shite might as well do all this once the cluster is removed (and mine is).
Like George Burns once said about getting old and tying your shoes, (now that I am down here what else can I do).
Same, now that dash/cluster is out what else can I do.
Thanks for all the valuable info moparmat.
That solid state sure is tiny compared to the stock IVR.
Sure as shite might as well do all this once the cluster is removed (and mine is).
Like George Burns once said about getting old and tying your shoes, (now that I am down here what else can I do).
Same, now that dash/cluster is out what else can I do.
Thanks for all the valuable info moparmat.
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