Alternator heat - how serious?

[Scott T-Bird]

I've never noticed it until the other day ... my alternator seems to heat up when I am charging on shore power. Is this normal?

Some background. I have 400 ah AGM house bank (2 - 4D batteries). The house bank has an "always on" charging buss with fused cable connections for the alternator and charger. The charger is 60-amp Sterling & alternator is 125 amp upgrade with Balmar 618 external regulator. I have BSS DCP switch and ACR.

For the first time ever, I neglected to switch on the main AC breaker when I left the boat after sailing, so my charger wasn't charging! I left without verifying it was on. I always leave the switch "ON" to run the fridge and a few fans. After a week away from the boat, the house bank was drained. I arrived in the evening a few days ago and began charging. The charger initially began charging at around 56 amps. Noting that the SOC was improving through the evening, I went to sleep. In the morning, I glanced at the regulator face and wondered a bit why the alternator temp reading was 45 d C!

My job for the day was to replace the coolant. I turned the alternator disconnect switch to "OFF" (I was going to reach around the alternator to open the coolant drain) and placed my hand on the alternator. Yikes it was hot! Not hot enough to burn my hand but 45 d C is 115 d F and that got my attention! By that time, I had been charging for at least 12 hours and the monitor said about 90% SOC. BTW, the battery temp was 32 d C and the boat was very warm from daytime temps in the 80's-90's and overnight temps in 70's, so I was never alarmed by the battery temps.

From that point on, I switched the alternator off when charging on AC power and only switched the alternator on (with AC OFF) when running the engine. The alternator appeared to be functioning normally and it never heated up again when charging on shore power.

I assume that the alternator is "hot" when I switch on the charger due to the common buss. Disconnecting the alternator at it's own isolation switch prevents the heating. But is it normal or unusual that the alternator should heat up this drastically when charging on shore power? I've never noticed this before, not that I've ever even considered it. Does anybody make a standard practice of disconnecting the alternator at an isolation switch when charging on shore power?

 

[Maine Sail]

I've never noticed it until the other day ... my alternator seems to heat up when I am charging on shore power. Is this normal?

Some background. I have 400 ah AGM house bank (2 - 4D batteries). The house bank has an "always on" charging buss with fused cable connections for the alternator and charger. The charger is 60-amp Sterling & alternator is 125 amp upgrade with Balmar 618 external regulator. I have BSS DCP switch and ACR.

For the first time ever, I neglected to switch on the main AC breaker when I left the boat after sailing, so my charger wasn't charging! I left without verifying it was on. I always leave the switch "ON" to run the fridge and a few fans. After a week away from the boat, the house bank was drained. I arrived in the evening a few days ago and began charging. The charger initially began charging at around 56 amps. Noting that the SOC was improving through the evening, I went to sleep. In the morning, I glanced at the regulator face and wondered a bit why the alternator temp reading was 45 d C!

My job for the day was to replace the coolant. I turned the alternator disconnect switch to "OFF" (I was going to reach around the alternator to open the coolant drain) and placed my hand on the alternator. Yikes it was hot! Not hot enough to burn my hand but 45 d C is 115 d F and that got my attention! By that time, I had been charging for at least 12 hours and the monitor said about 90% SOC. BTW, the battery temp was 32 d C and the boat was very warm from daytime temps in the 80's-90's and overnight temps in 70's, so I was never alarmed by the battery temps.

From that point on, I switched the alternator off when charging on AC power and only switched the alternator on (with AC OFF) when running the engine. The alternator appeared to be functioning normally and it never heated up again when charging on shore power.

I assume that the alternator is "hot" when I switch on the charger due to the common buss. Disconnecting the alternator at it's own isolation switch prevents the heating. But is it normal or unusual that the alternator should heat up this drastically when charging on shore power? I've never noticed this before, not that I've ever even considered it. Does anybody make a standard practice of disconnecting the alternator at an isolation switch when charging on shore power?

The reg should not be active when engine ignition is off.. Make sure brown reg wire does not have 12V on it..

 

[Scott T-Bird]

The reg should not be active when engine ignition is off.. Make sure brown reg wire does not have 12V on it..

I'm pretty sure the regulator is always active since I was reading it when laying in bed (it's mounted outside the engine compartment inside the aft cabin). So, the brown wire should be connected only to the keyed side of the ignition switch? Is there any harm to be expected if it has been incorrect for a long time? I'm pretty sure that I wired it in the same manner that I found the 614 wired from the previous owner's installation.

 

[Ward H]

So, the brown wire should be connected only to the keyed side of the ignition switch?

That's how mine is wired. Maybe PO got it wrong?

Is there any harm to be expected if it has been incorrect for a long time?

I think you should replace it with new and sell the old one to me for $50.
I'd be more concerned about the alternator sitting there hot but if it appears to be working and you fixed the wring I wouldn't worry about it.

 

[jviss]

That's not right or normal, in my opinion, Scott. What's causing the heat? It must be current flowing through the alternator, but that shouldn't be the case when charging via shore power.

But then, I've never really thought about it much. Assuming there aren't any failed components, the only place the heat could be coming from is from field current.

How is the alternator disconnect switch wired?

 

[Hello Below]

So, the brown wire should be connected only to the keyed side of the ignition switch?

Scott the manual for the MC-618 page 6 (identical to the MC-614 install instructions) states:
“Install BROWN Ignition Wire
The BROWN Ignition Wire #3 in diagram at right provides ON/OFF voltage for the regulator. This wire is included in the Ford-style plug at the regulator end of the wiring harness. The other end of the wire is fitted with a butt connector. Typically, the ignition wire is connected to the ON side of the ignition switch. This may be at the actual switch, or to a wire in the existing engine wiring loom that delivers switched voltage from the ignition switch. In some cases, an oil pressure switch may be used to activate the regulator. In either case, the regulator’s ignition wire must see zero volts when the engine ignition is switched off.”

As Mainesail has posted above:

The reg should not be active when engine ignition is off.. Make sure brown reg wire does not have 12V on it..

 

[Scott T-Bird]

How is the alternator disconnect switch wired?

Yes, even if the ignition wire is connected to an always "on" wire in the loom, I don't understand why there would be heat when charger is on.

The alternator disconnect switch is between the cable from the alternator and a cable to the 4-post buss. I believe the cables are 2 AWG and the fuse at the buss is 150 amp. The buss is "ON" as long as the HOUSE isolation switch is "ON". The buss has 4 posts, which also include cables to the HOUSE iso switch, ACR, and the AC charger. The HOUSE Bank is connected directly to the HOUSE iso switch on the power in side. The load side of the switch feeds the buss and the HOUSE side of the DCP on my panel.

Perhaps the alternator reacts because it has 12v supply from the common buss and 12v also hot from the ignition wire (which means the blue field wire sees voltage). I recall performing the tests and did not find any issues at the time of installation. In Test 2 the blue field wire sees voltage when the ignition input is hot but 0 volts when ignition input is 0 volts. I do recall the terminals are so tiny it is very difficult to make the multimeter leads connect during the tests. Perhaps I was reading 0 volts on the ignition input when actually it was hot during Test 1. I may not have discovered this issue while testing the installation. It's always very difficult to perform these tasks when lying on my back in tight quarters, without any room to get a good view of the multimeter while at the same time trying to fumble with the leads.

My diagram looks like this except I don't have solar, my cable goes directly from the HOUSE iso switch to the DCP switch, and I have alternator disconnect between the buss and the alternator.

 

[Scott T-Bird]

Scott the manual for the MC-618 page 6 (identical to the MC-614 install instructions) states:
“Install BROWN Ignition Wire
The BROWN Ignition Wire #3 in diagram at right provides ON/OFF voltage for the regulator. This wire is included in the Ford-style plug at the regulator end of the wiring harness. The other end of the wire is fitted with a butt connector. Typically, the ignition wire is connected to the ON side of the ignition switch. This may be at the actual switch, or to a wire in the existing engine wiring loom that delivers switched voltage from the ignition switch. In some cases, an oil pressure switch may be used to activate the regulator. In either case, the regulator’s ignition wire must see zero volts when the engine ignition is switched off.”

As Mainesail has posted above:

Would that cause heat? I did the tests after installing the wiring and I believe I verified each condition for both tests (ignition on and ignition off). But perhaps I wasn't making connection during the first test as explained above. Will 12v power from 2 sources - charger thru the buss and field wire through the ignition cause this heat?

In any case, I will be checking the brown wire connection when I get back to the boat.

Is this a condition that may cause damage? I haven't noticed any problems with the alternator or the regulator. I do get curious OVER VOLTAGE messages on the Balmar monitor occasionally when I get back to the boat and I haven't figured out the reason. Perhaps this is connected. My batteries haven't been affected as far as I can tell.

 

[Hello Below]

Maybe, as a trial, rewire the regulator as per the manual and then again try charging from your shore power charger after depleting your batteries SOC somewhat. See if the alternator warms up or heats up. From my experience, I suggest it will not.

 

[Maine Sail]

I'm pretty sure the regulator is always active since I was reading it when laying in bed (it's mounted outside the engine compartment inside the aft cabin). So, the brown wire should be connected only to the keyed side of the ignition switch? Is there any harm to be expected if it has been incorrect for a long time? I'm pretty sure that I wired it in the same manner that I found the 614 wired from the previous owner's installation.

Not good at all for the reg as it just sits there pumping full field 24/7. The brown wire is what turns it on when you start the engine..

 

[Scott T-Bird]

So I got back to the boat yesterday and found the brown ignition input wire connected with a male spade to a fitting similar to "Connector 1" as shown in the diagram below. The difference is that the connector appeared to originate at the starter in a wiring loom and it was very difficult to locate the same wires on the starter. I think that I simply duplicated the wiring method that the previous owner used, thinking that it would be a suitable connection.

I looked for an easy way to connect the wire to the "on" side of the ignition switch and found that it would not be a simple task - first to identify a suitable connection, and secondly, to physically make any wire connection in the restricted confines of the engine compartment. We wanted to go sailing so I looked for an easier solution.

Instead, I connected it to the oil pressure switch. It was a simple connection with a ring terminal at the face of the engine and the oil pressure switch was mentioned in the manual as an alternative. That worked fine, but I also noted that the regulator only activated when the engine was running, not when the start switch is "on". The manual also covers this condition. Currently, I can only adjust alternator settings with the engine running. I will eventually run a wire back to the brown wire from the control panel wiring. I think that will be the easiest way to make a connection so that the regulator is activated with ignition switch "on".