relay powered voltage regulator ?

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65-440

65-440

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Talked to Mark from mad electrical earlier, he was recommending after I finished the amp gauge bypass that I should consider using a relay to power my voltage regulator.after he explained everything, it made perfect sense instead of using power" downstream" from the ignition switch. Instead it would get raw voltage from the alternator and make the charging system more precise. I was just wondering how many of you guys are doing this, and did you notice anything different?
 
Yes and no. You do NOT want the VR power lead to "sense" the alternator, you want to tie this just as close to the battery, voltage wise, as you can get...........

which is why I'm always preaching voltage drop in both the harness and ground. "Drop" in either will cause the VR to raise charging voltage at the battery

Relays are what I use to run most "heavy" ignition loads. I have one for ignition / charging (field and VR) for EFI, and fuel pump. I have two more for hi/lo beam headlights.

The easy way is to cut the ignition switched wire coming out of the bulkhead. Mount a good quality relay, and run a fused power lead to one contact. A good source is the large starter relay stud.

The switched contact goes to the blue wire you cut feeding to the ignition / VR

The other cut lead, coming out of the bulkhead, goes to the relay coil

You ground the remaining relay coil connection. One thing you need to be careful with Bosch style and knockoff relays is, some have a diode internally to protect the switching circuit. This means one specific coil terminal must be ground

Se below:

86 is ground, 85 goes to the ignition feed you cut coming out of the bulkhead

30 feeds 12V in from a fuse from the starter relay stud

87A is "normally closed" and not used

87 would go off to feed power to the VR and ignition.

bosch_relay.gif
 
THE DIFFERENCE between sensing at the alternator stud and the battery:

The reason you want the VR to sense "at the battery" is because it is the target!!! LOL that you are trying to charge.

If you have a battery that is low, and or a too small charging wire for the size of the alternator there will be voltage drop in the charging wire under heavy load

What this means is, if the VR is properly regulating at 13.8--14.2 and is connected to the alternator output, then the battery will be seeing LESS voltage.

This is one reason I don't care for "one wire" setups for many applications.

Another reason is your loads and accessories. If they are tapped off near the battery, they will also see low voltage compared to the alternator.

The original systems WERE ALL intended to be "sensed" at the battery, not the charging device. It wasn't until "one wire" setups came into vogue that this changed.

If a "one wire" has what amounts to an oversized charging wire, there is no real problem. Someplace there used to be a recommendation chart for charging wire size for Delco "one wire." They didn't get "very big" (amps output) before stuff like a no 6 wire was specified.
 
But once the amp gauge bypass is compete, the black alternator wire now goes directly to the starter relay battery stud. If you put a VR relay powered buy that stud, isn't that going to see alternator output voltage?
 
This is going to depend on how big the wire is going to the alternator, how long it is, and how much current is going through there. That is what voltage drop is all about.

The smaller the wire, the longer the wire, and the more current, the more voltage drop.
 
Power not just Vreg via the relay, but all underhood that use "ignition" power. In other words, don't snip the Vreg power wire, but tap into it there or somewhere else more convenient, like the ballast resistor upstream side.
 
Think I'll wait and see where my voltage drop is after I finish bypassing the amp gauge. Should be wrapped up this morning. Did find some suspects when taking things apart, hopefully good to go after this!
 
I'm looking at doing this same mod on my 73 Duster after talking to Mark from MAD electrical, too. I've already done the alternator bypass and I just finished running my headlight relays. He actually sent me a diagram of how to install the relay, but I'm still kind of confused as to what wire I'm supposed to use for "Ignition Feed" (85 terminal). Is there a specific wire to splice into for this? Also, just to clarify the 87 terminal just get spliced into the blue VR wire, right? I recently replaced the pigtail on my VR, so I was just going to cut into that splice.
 
Unprovoked said:
I'm looking at doing this same mod on my 73 Duster after talking to Mark from MAD electrical, too. I've already done the alternator bypass and I just finished running my headlight relays. He actually sent me a diagram of how to install the relay, but I'm still kind of confused as to what wire I'm supposed to use for "Ignition Feed" (85 terminal). Is there a specific wire to splice into for this? Also, just to clarify the 87 terminal just get spliced into the blue VR wire, right? I recently replaced the pigtail on my VR, so I was just going to cut into that splice.
Click to expand...

cut regulator ign wire, blue

take other end of cut wire coming from harness to relay 86

run regulator ign end of wire to relay 87

run 10A inline fuse off starter relay stud to relay 30

ground relay 85

similar to below.





Image1.gif
 
If your schematic is used with a Bosch relay that has the internal diode, it will blow the diode, and perhaps damage wiring. The fix is to switch connections on terminals 85 and 86. Ground should be on terminal 86.
 
KitCarlson said:
If your schematic is used with a Bosch relay that has the internal diode, it will blow the diode, and perhaps damage wiring. The fix is to switch connections on terminals 85 and 86. Ground should be on terminal 86.
Click to expand...

Word.
 

Attachments

  • positive_switch.gif
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The diode protects a transistor if it is used to drive the relay. When the transistor is turned off, the diode recirculates the current so high voltage is reduced as transistor opens. It protects against inductive kick. In the normal turning on, the diode is reversed biased, and has no effect then.

If wired as post #9, the diode is forward biased, it has only 0.7V of voltage drop. If 12V is applied it goes pow, and results in a dead short, if it is not blown open. Semiconductors most often fail shorted, not open.

Some may say I wired like that and it worked, that is because your particular relay does not have the diode.

TrailBeast posted correct schematic.
 
I have seen relays with a diode oriented both ways between terminals 85 & 86. There is a post w/ photos just about relays, I recall on this forum, discussing that and more. I recall the "wrong" orientation was on a relay base sold by an audio parts company. If a diode (or resistor) is internal to the relay, it is usually depicted on the side of the relay. The terminal numbers aren't arbitrary but based on a European standard (German DIN). I see the same numbers in my M-B wiring diagrams. However, when I compare relay numbering w/ the DIN list, they don't exactly match, so perhaps some numbers are an earlier Bosch numbering.
 
KitCarlson said:
If wired as post #9, the diode is forward biased,........it goes pow, and results in a dead short,

TrailBeast posted correct schematic.
Click to expand...

BillGrissom said:
I have seen relays with a diode oriented both ways between terminals 85 & 86. .
Click to expand...


i donoo. notes i have is correct as to post 9 check with meter / test lamp

according to this 86 should be positive

bowery.com/maserati/home/files/bosch%20relays.pdf
 
That is good information. It is always good to know the relay by reading the data sheet, or imprints on the relay. Wire per relay and task. Since the diode is in parallel with relay coil, it might be difficult to use meter to locate polarity of diode.

I buy relays from places like Digikey, Mouser, or Partsexpress. I avoid the high priced junk, often found at auto parts stores wiring section.
 
BillGrissom said:
Power not just Vreg via the relay, but all underhood that use "ignition" power. In other words, don't snip the Vreg power wire, but tap into it there or somewhere else more convenient, like the ballast resistor upstream side.
Click to expand...

I've got a question about this. If I have done the ammeter bypass and am hooking up the Classic HEI Kit:
I will have one relay for the GM coil power.
I will achieve this by joining the blue and brown wire from the ballast to contact 86 on my relay. Contact 87 will then have my red+ wire for the GM coil.

Do I need to add yet another relay for the ignition circuit?
That is, the circuit that ties into the voltage regulator?

I hope my question makes sense.
 
Saverio said:
I've got a question about this. If I have done the ammeter bypass and am hooking up the Classic HEI Kit:
I will have one relay for the GM coil power.
I will achieve this by joining the blue and brown wire from the ballast to contact 86 on my relay. Contact 87 will then have my red+ wire for the GM coil.

Do I need to add yet another relay for the ignition circuit?
That is, the circuit that ties into the voltage regulator?

I hope my question makes sense.
Click to expand...

If the relay you use has the internal diode just switch the 86 and 87 terminals to the diagram you sent me, instead of the one I sent you. :D

The regulator relay is a separate mod to do for stabilizing the charging system voltage via sensing the voltage at a different location that does not suffer the voltage drop of a long older run of wires.

Maybe the next electrical project? :D
 
Definitely! Once I get the HEI Kit all set up, I'm going to to tackle adding that relay next. 👍🏽
 
Hi,I know this is a old post but I need some clarification on this do I still use the resistor to feed the coil does someone have a schematic on this that would help me out I have been pulling my hair out trying to fix the over charging on my Boy'S car. Thanks for any help KB9GIB.
 
KB9GIB said:
Hi,I know this is a old post but I need some clarification on this do I still use the resistor to feed the coil does someone have a schematic on this that would help me out I have been pulling my hair out trying to fix the over charging on my Boy'S car. Thanks for any help KB9GIB.
Click to expand...

The blue wire that goes into the voltage regulator gets cut.
That blue wire on the harness side now activates the relay via terminal 86 , and the regulator side of the cut blue wire now goes to relay terminal 30 on the relay.
The harness side of the blue wire is where the regulator senses voltage, so now instead of sensing that voltage through all that harness it sense it directly from the battery.
Terminals 85 and 86 close the relay when you turn on the key.
87 and 30 are where power passes through when the relay is activated.
This gives a much more precise reading of battery voltage for the regulator to sense from, instead of it thinking the voltage is always low because of a voltage drop across the harness.
Use a non resisted 4 terminal relay.

Works great.

relay reg.jpg
 
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TrailBeast said:
The blue wire that goes into the voltage regulator gets cut.
That blue wire on the harness side now activates the relay via terminal 86 , and the regulator side of the cut blue wire now goes to relay terminal 30 on the relay.
The harness side of the blue wire is where the regulator senses voltage, so now instead of sensing that voltage through all that harness it sense it directly from the battery.
Terminals 85 and 86 close the relay when you turn on the key.
87 and 30 are where power passes through when the relay is activated.
This gives a much more precise reading of battery voltage for the regulator to sense from, instead of it thinking the voltage is always low because of a voltage drop across the harness.
Use a non resisted 4 terminal relay.

Works great.

View attachment 1715020926
Click to expand...
Thank you Trail beast, That cleared it all up for me thank very much.KB9GIB
 
TrailBeast said:
The blue wire that goes into the voltage regulator gets cut.
That blue wire on the harness side now activates the relay via terminal 86 , and the regulator side of the cut blue wire now goes to relay terminal 30 on the relay.
The harness side of the blue wire is where the regulator senses voltage, so now instead of sensing that voltage through all that harness it sense it directly from the battery.
Terminals 85 and 86 close the relay when you turn on the key.
87 and 30 are where power passes through when the relay is activated.
This gives a much more precise reading of battery voltage for the regulator to sense from, instead of it thinking the voltage is always low because of a voltage drop across the harness.
Use a non resisted 4 terminal relay.

Works great.

View attachment 1715020926
Click to expand...
 
TrailBeast, Do you happen to have a name are part number on the non resisted 4 terminal relay I can not find one local you know how it is you have to have rank and serial number are they cant find nothing.Thanks KB9GIB
 
KB9GIB said:
TrailBeast, Do you happen to have a name are part number on the non resisted 4 terminal relay I can not find one local you know how it is you have to have rank and serial number are they cant find nothing.Thanks KB9GIB
Click to expand...

You can use the resisted type as it's not a huge deal.
Here is a Napa part that will work just fine.
Electrical Relay - Universal - H/D Truck

There is also Dorman Part Number: 88069 at Autozone.

If you end up with a 5 terminal relay just ignore terminal 87A.
Relays with the 87A terminal can be used for normally open or normally closed switching both, so ignoring terminal 87A makes it a normally open circuit until the key is turned.
 
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