Blue Sea ACR Wiring Question

[dwh]

Yup. A.K.A. Bosch relay.

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[Tiktaalik]

This is the gauge I have: https://ebay.us/v90Dcn

I assume it’s very low draw so what is the lowest draw relay you can buy for a gauge like this?

It says that it has “Built in over current, over voltage and short circuit protection,
it well protects the whole circuit.”

Does that mean I don’t need to fuse it?

 

[luthj]

You still need to fuse the wires that feed it.

 

[dwh]

That thing draws milliamps. A 1a fuse should be enough. As for the relay, your bog standard Bosch relay has a 30a rating and costs like 5 bucks. Billions of those in use in vehicles, you could probably snag one out of a fusebox in any junkyard.

 

[dwh]

And that "buit-in protection" probably means it has a cheezy fuse soldered to the board inside. Hook it up wrong, blow the fuse, throw it away.

 

[Tiktaalik]

I'm getting closer to installing my dual battery system but I have been having an issue with my alternator for quite some time that I can't seem to be able to resolve. I rebuilt the stock alternator about a year ago. Then the regulator crapped out so I replaced it with an adjustable regulator. Following that the alternator seemed to modestly trickle charge at idle but stop at revving. So I ordered a Reman Bosch Alternator and installed an adjustable regulator on that one. Same deal. I took it out this past weekend and put a new regulator on it with no change. I have checked engine and alternator grounds, checked for parasitic draws and done load tests. No issues there. If the dash charge light is grounded the light comes on but it refuses to come on otherwise.

There are two wires coming from the alternator. A red charge wire and a blue wire that I assume is the dash charge indicator light circuit. These two wires go to a junction box in my engine compartment. On the other side of that box six wires are connected. I'm assuming that those six wires are charge light/battery/starter/fuse panel and some other stuff. They are referred to as "Starter Control Power Supply" in the manual. I have the wiring diagram but don't know how to read it. I can post it up here if it helps.

Any ideas to what the issue might be? My next step is to pull the alternator again and take it back to the shop to get it tested. Is there anything else in the system (like a switch or relay) that could prevent the alternator from charging properly? Or is it just a strange coincidence that the "new" alternator also is not charging?

 

[luthj]

What voltage is the alternator outputting? Both at its terminals, and at the battery or distribution block? If its not making the correct voltage you have an issue. If its making the correct voltage, and its reaching the battery, there is nothing wrong.

 

[Tiktaalik]

I’ve done it so many times now that I can’t recall so I will measure again over the weekend. I know how to measure the battery but what is the proper way to measure at the distribution block and at the alternator terminals? One probe on alternator and the other on distribution block or on back of alternator output?

When I start up, the battery level (measured at battery) slowly start to climb ever so slightly but when reving the engine it stops climbing. I find that puzzling. I’m used to the alternator output increasing significantly when you rev the engine.

Other than a bad ground, is there anything else that would prevent the regulator from functioning properly?

What voltage is the alternator outputting? Both at its terminals, and at the battery or distribution block? If its not making the correct voltage you have an issue. If its making the correct voltage, and its reaching the battery, there is nothing wrong.

 

[luthj]

Your understanding of how charging dynamics work is a bit inaccurate. Battery charge rate is determined by voltage at the battery terminals and the battery SOC. Voltage at the terminals is a combination of wiring voltage drops and alternator voltage. Voltage drops are determined by wiring size and the charge rate. So its all part of the same equation.

Unless you are maxing out the alternators output current, the voltage will not change significantly with increased RPM.

If the battery is within 0.1V of the alternator voltage, then everything is working properly. Obviously you are looking for higher voltages in this range, 14.4V is ideal for deep cycle charging, but anything over 14V is pretty good.

Measure the voltage at the battery terminals (put the probes on the positive and negative). Measure voltage at other locations referenced to a convenient ground, engine block, battery negative etc. If you have significant voltage drop between the alternator and the battery you need to asses where its happening.


Typical alternator voltage is 13.8-14.2V.

 

[Tiktaalik]

You’re absolutely correct! My understanding is definitely inaccurate. I’m new at this and learning as I go. There’s a chance that it is working correctly after all and I am misunderstanding the whole thing. I have kept it on a trickle charger every night because I’m worried about running low driving to/from work.

I was just expecting the voltage to rapidly increase and decrease as I rev the engine because that is how other cars I tested, behaved. The other thing is that the dash charge light isn’t coming. If I unplug it and ground it, it does so I know it’s working.

I have a remanufactured 60A Bosch alternator that we installed an adjustable regulator on and set it to 14.7v. That was down because the Odyssey label recommends it and an Odyssey rep had mentioned that this deep cycle battery needs higher voltage or you kill it over time.

Here is a video for reference. I was expecting it to peak at 14.7v when reviving but it doesn’t. According to my alternator guy he said it is not working correctly and that I need to take it in:

 

[DaveInDenver]

The alternator is either not working or not wired correctly. You're measuring the battery voltage for sure, though, you see it cranking and recovering a bit.

Are you sure that's an externally regulated alternator you have? Having just one or two wires implies to me that it's internally regulated.

 

[Tiktaalik]

Perhaps I wired it up wrong. The original alternator had two wires. A red charge wire and a blue dash charge indication light wire. The new alternator has a 3 prong plug so I made a new 8AWG charge wire (twice as thick as the old one) and split that into two separate connectors that were then inserted into the plug on the alternator end. Then I inserted the other end at the same spot at the distribution box. Perhaps this combined charge cable needs to be two separate wires and go to two different spots in the distribution box? If I were to purchase that plug and wires, the three are separate. Could that be the issue? The original alternator only had one so that’s the part I don’t get.

 

[luthj]

That alternator is probably not self exciting. In which case you need to supply a some voltage through the proper wire for it to start charging. This should be done through the D+ wire (this will be how it was wired from the factory). Usually the instrument cluster has a light which supplies power through the D+. This serves the purpose of exciting the alternator to start charging, and also serves as an indicator light. If the alternator is not charging, this light will see ground on the alternator side, thus illuminating. In some cases the factory light is not sufficient to excite the alternator.

In your case it sounds like the regulator may not be functioning properly.

 

[DaveInDenver]

The B+ should just go straight to the battery.

The domed black part is Bosch p/n 30090 (or similar like 1197311090) is the voltage regulator.

The D+ terminal is probably (maybe?) for a tach or dash light. That might function as the charge, so it would need run from an ignition hot source.

The black box is probably the suppression capacitor (does it say or is marked 2.2 μF?) , something like Bosch p/n 0290800052.

ETA:
https://www.aussiev8.com.au/holden-v8s/52316-bosch-alternator-wiring-torana-please-help.html

"The Bosch alternator is incapable of self-excitation, or "boot-strapping" itself to an operating condition. Older DC generators and some U.S. alternators have residual magnetism retained in the core, or some other scheme to get enough field current to get themselves up and running. The Bosch alternator uses a different scheme. The charge warning lamp is connected between the ignition switch and the D+ terminal. When the car is first started, there is no output from the alternator at either the B+ or D+ terminals. The voltage regulator, sensing no output, is attempting to command maximum field current... it effectively shorts the D+ and DF terminals together. This places the D+ terminal close to ground potential, because the resistance of the field winding is not large. This means that there is +12 volts on one side of the charge warning lamp, and the other side of the lamp is grounded through the alternator field winding.

Current thus flows through the lamp, lighting it. This same current, however, also flows through the alternator field winding, producing a magnetic field. This magnetic field is what the alternator needs to start up, and if everything is working correctly, that's exactly what happens. The alternator now begins to develop identical voltages at the D+ and B+ terminals. The D+ terminal is connected to one end of the charge warning lamp, while the other end of the lamp is connected to the battery via the ignition switch. Since the B+ terminal is hard-wired to the battery, and since both the D+ and B+ diodes are fed from the same set of windings in the alternator, no voltage difference can exist between these two points. The warning lamp goes out.

The voltage regulator "watches" the voltage at the D+ point, which should be the same as that applied to the battery. It now changes the short between the D+ and DF terminals into a variable resistance. This effectively controls the field current (whose source is now the output from the D+ terminal, and not the charge warning lamp) and thus regulates the output voltage of the alternator."

 

[luthj]

Those bosch alternators have external regulators (adjustable, or fully digital charging) available. You can also use a simple diode to boost the output if its low. You may find that the regulators target voltage is quite low (13.4-13.6V). Adding a diode can boost that by 0.20-0.4V, which puts you square in the the 13.8 (min) to 14.2V(ideally) charging range. Obviously you have some other issue currently, but this may be a consideration down the road to get good performance (and brighter headlights).

That alternator looks pretty similar to the alternators VW used on many 70-80s vehicles. You may be able to retrofit a 90A unit. If you have the space, the later model (self exciting, mid 90s VW cars) units up to 120A may fit with a custom bracket and pulley swap.