Alternator

Topic: Alternator (Read 1420 times) previous topic - next topic

Alternator

July 14, 2012, 06:22:34 pm

I'm starting a new thread on this as it isn't an engine battery issue. After having the alternator replaced at a truck shop the summer before last I thought everything was good until I noticed that either of my batteries alone powered the coach & chassis. After testing for bad boost solenoid or isolator...I determined that the alternator is the culprit. Once disconnected...the house is running off just the house battery again. The main problem was there is no wire (at least anymore) to excite the alternator. There is a negative battery type cable, positive battery type cable and smaller sense wire wired directly to the chassis battery, which I've proven as the voltage is the same or nearly so and is only hot when the chassis battery is connected. When the geniuses at Empire Freightliner in Jackson, MS couldn't get the alternator to charge they ran a jumper wire from the main positive post on the alternator to the sense post (with sense wire there also). I guess that excites the alternator somehow. Looking at the isolator wiring, the alternator's main output goes to the center post of the isolator and with the sense wire wired directly to the chassis battery, voltage has been passing through that jumper from the sense line to the center post of the isolator, which has connections to both sides of the isolator (externally) thus defeating or bypassing the isolator. I've been feeding 12V from the chassis battery via the sense wire through that jumper to the center post of the isolator continuously! I'm very surprised that I don't have a four wire alternator like everyone else seems to have unless the aforementioned geniuses at Empire did away with it. I'm not sure how to proceed. I suppose I could do as Brett says and "find" 12V that is only hot with the ignition in the engine bay somewhere and add it to a replacement four wire alternator. The auto electric guy says the four wire alternators have a post for voltage that is only on with the ignition to tell the alternator to start working. My alternator has a post marked "I" but the description of it on their website says this: "I" Terminal - The Indicator lamp/ignition terminal can serve as a current source, sink or both, depending on how it is connected. The diagram above shows one configuration. Current capability is 1.0 Amp in either direction." This doesn't sound like the forth post that needs current from the ignition to make it work. Right now I guess I should find a true four post alternator and find a 12V source hot from the ignition in the engine bay. Any suggestions on what to tap? Be very careful if ever replacing an alternator at a truck repair facility.

Re: Alternator

Reply #1 – July 14, 2012, 07:36:04 pm

Because trucks do not have voltage isolators (or at least only a few - with condos and generators - do) truck stop mechanics may not be familiar with 4-wire systems. These folks commonly jumper the connectors. In fact they have shop manuals that tell them (and show them how) to jumper them.

On my 1993 U225 there is an isolator board on the driver's side just aft of the rear wheel. It's accessed by a bay door and if you squat down and look straight in the isolator is on your left mounted on a vertical board. The isolator itself has fins on it. Also on that board are a bunch of solenoids. One of these is the solenoid that routes 12vdc from your ignition to the alternator.

The wire is red... or it used to be red... my wife insists that it is pink. Okay... maybe it faded a little. Unless one of the folks here can come up with a more specific alternative, what I'd do is look at each wire coming off all the solenoids and test to see if there is a red one that shifts to +12vdc when the ignition key is turned on.

I found this well-written explanation of how to wire up 4-wire alternators when I did a search for Hehr Powerline Alternators (which is one of the brands FT installed in their coaches).

This is the link to the pdf: http://www.hehrintl.com/pdf/S25TS.pdf

On page 4 you will see a drawing of the back of the typical Leece-Neville type alternator with a bunch of jumpers installed. The jumper (E) between (B) and (C) should not be installed on your alternator.

The red (okay, pink... jeez) wire from the isolator should connect to (B) and the wire directly from the battery should connect to (C). There should not be a jumper (F) between terminal (C) and terminal (I).

Following Gary's lead I went to the remote start panel at the engine itself and selected the termainal that had +12vd on it all the time on the ON/OFF switch and ran a wire from that point to the (C) terminal on the alternator.

There should also NOT be +12vdc between terminals (J) (the negative out put terminal) and (I (the positive output terminal unless the engine is running (and the alternator is working).

At the bottom of page 5 you will see an explanation of jumpers for when there is an isolator. Apparently very few mechanics have seen this explanation.

I don't have a drawing of the isolator board handy but I'm sure someone does. That should show you the location (and terminal) from which the +12vdc ignition wire (the red - or maybe pink - wire) that goes to (B) on the alternator.

I hope this is more clear than I'm afraid it is.

Craig

Re: Alternator

Reply #2 – July 15, 2012, 01:10:20 am

Thanks. I have a wire from the engine battery with 12V all the time. I have the big POS & NEG wires. I need a wire that goes hot with the ignition somewhere near the alternator. I am going to look around to see if there are signs that a wire was cut and taped up. If nothing stands out I will look for the red or pink wire at the solenoid you mentioned. Mine is in the same spot.

Re: Alternator

Reply #3 – July 15, 2012, 10:43:58 am

Dwayne and Craig,
Karma to you both for flowing that info up. I appreciate it because I am sure I will be referring to it at some point in the future.
Rick
Currently a Fort Peck COE,Fort Peck, MT headed east

Re: Alternator

Reply #4 – July 15, 2012, 02:42:12 pm

In this schematic that Pierce sent me I can see the four wires on the inside post of the isolator go to the boost solenoid on the isolator panel, the ignition solenoid in the dash, the aux start solenoid on the isolator panel and the alternator exciter. I have four wires on the inside post. I'm going to have to trace them as one of them is covered in a plastic tube that looks exactly like the wire I've been assuming is the alternator sense wire to the battery. There is 12V on it all the time though (which is why I thought it the sense wire). If I'm reading this schematic correctly, the inside post on the isolator should only be hot with the ignition...or am I wrong?

Re: Alternator

Reply #5 – July 15, 2012, 02:50:12 pm

Quote from: Dwayne – July 15, 2012, 01:10:20 am

Thanks. I have a wire from the engine battery with 12V all the time. I have the big POS & NEG wires. I need a wire that goes hot with the ignition somewhere near the alternator. I am going to look around to see if there are signs that a wire was cut and taped up. If nothing stands out I will look for the red or pink wire at the solenoid you mentioned. Mine is in the same spot.

Looking at the wiring diagram again to refresh my memory. There are two wires off the isolator itself that are marked as going to the alternator. One of them could be the red/pink wire. I might be confusing a wire from one of the solenoids that simply disintegrated when I touched it and had to be repaired.

There is a wire bundle near the alternator where that red/pink wire exits... you should be able to see it somewhere (although our wiring could be different with Cummins for me and Cat for you).

But you're zeroing in on it.

Craig

Re: Alternator

Reply #6 – July 15, 2012, 03:05:00 pm

Looking at that schematic again, obviously the inside post on the isolator is engine battery and hot all the time. The wire that goes from there to the ignition provides power for the ignition. Nowhere on this schematic is the sense wire from the engine battery to the alternator, which I know must be present so that the alternator knows the voltage of the engine battery. If that excite wire is coming off that inside post on the isolator it must be hot all the time and not dependent on ignition. I hope my understanding of the four wires at the alternator is accurate: big POS to middle post on isolator, NEG to ground, sense wire to engine battery and excite wire providing 12V and according to that schematic it should come directly from the inside post on the isolator.

Re: Alternator

Reply #7 – July 15, 2012, 03:24:22 pm

Dwayne: I could not find a "sense" wire directly from the batteries either. My alternator had a jumper that provided the sensing (but was 0.6vdc lower than the "real" battery voltage because it came through the isolator). I followed Gary B's suggestion and simply added a wire from the hot side of the ON/OFF remote engine start switch. This has worked pretty well although, in my opinion, the entire system needs to be re-designed in light of what we now know about battery charging.

Once I get the solar panels and the MPPT controller installed I plan to simply switch off the engine alternator whenever we're traveling during the day (which is almost always) and let the solar panels do the work (with the boost switch on).

Craig

Re: Alternator

Reply #8 – July 15, 2012, 06:21:47 pm

Well, this is going to make me sound stupid but I don't know if I have a remote engine start switch. Where in the engine bay is yours? Is the 12V off that wire a more accurate representation of battery voltage than the engine side of the isolator?

Re: Alternator

Reply #9 – July 15, 2012, 07:42:19 pm

Quote from: Dwayne – July 15, 2012, 06:21:47 pm

Well, this is going to make me sound stupid but I don't know if I have a remote engine start switch. Where in the engine bay is yours? Is the 12V off that wire a more accurate representation of battery voltage than the engine side of the isolator?

On my U225, which has the Cummins 5.9B engine, the remote start is right at the back above the radiator and clearly marked with an ON/OFF toggle switch and a start switch. I've never actually tried it though. Yours will probably be in a different position given the side radiator.

As far as locating a reasonable sense voltage, use a digital voltmeter and measure your starting battery at the terminals. Then check the voltages of the possible alternative 12vdc "sense" terminals. If they are on the "wrong" side of the isolator diode they will be about 0.6vdc lower than the voltage at the battery terminals. I do not think you want this as sense voltage as the regulator will make the alternator work harder to charge up what it thinks is a low battery. What you want will be pretty close to the voltage at the battery itself (within a tenth of a volt) and will not be switched on and off by the ignition key.

Craig

Re: Alternator

Reply #10 – July 15, 2012, 10:10:14 pm

Dwayne,

Open the back engine access area. Just off center on the "roof" is the air filter minder and remote start switch.

Brett

Re: Alternator

Reply #11 – July 15, 2012, 10:17:53 pm

My air filter minder is inside on the left but down low inboard of the fluid tank for the hyd. fan motor.

Re: Alternator

Reply #12 – July 15, 2012, 10:40:45 pm

Sorry...just outboard of the tank. I was looking for a photo and found this one with the old alternator. It was the Hehr Powerline. Can anyone who has or had a coach from this era tell me how many wires this alternator had?

Re: Alternator

Reply #13 – July 15, 2012, 11:38:36 pm

Quote from: Dwayne – July 15, 2012, 10:40:45 pm

Sorry...just outboard of the tank. I was looking for a photo and found this one with the old alternator. It was the Hehr Powerline. Can anyone who has or had a coach from this era tell me how many wires this alternator had?

Four. The Hehr Powerline is the same as the Leece-Neville. I have one on my U225. See the link to the .pdf on the Hehr Powerline I posted above. It explains everything.

Craig

Re: Alternator

Reply #14 – July 16, 2012, 09:14:17 am

I looked at that but I'm still confused. I just need to confirm that I probably had four wires to the old Powerline alternator. POS to center post of isolator, NEG to ground, Sense to engine battery post of isolator and exciter from 12V with ignition on. The auto electric guy thinks it should have one with the Duvac post. Does the exciter wire or the sense wire go to this post? Also, I have no remote engine start. I did see one wire taped off near the alternator. See photo. Perhaps the truck shop in Jackson cut the wire off at this spot.

Re: Alternator

Reply #15 – July 16, 2012, 09:45:28 am

I guess replying to myself is the same as talking to myself (which I do frequently)...talked to Delco Remy. There alternator will work but it needs momentary 12V to the output post to excite the alternator. But you can't just hook up any 12V wire to it as once it starts outputting all that voltage is coming back down the wire. So, the tech said that some people rig a starter solenoid with a manual on/off switch and others use a diode on the line to prevent voltage from back feeding on whatever 12V source you are using. Guess I'll explain this to the auto electric guy and see what he says.

Re: Alternator

Reply #16 – July 16, 2012, 11:17:03 am

Quote from: Dwayne – July 16, 2012, 09:14:17 am

I looked at that but I'm still confused. I just need to confirm that I probably had four wires to the old Powerline alternator. POS to center post of isolator, NEG to ground, Sense to engine battery post of isolator and exciter from 12V with ignition on. The auto electric guy thinks it should have one with the Duvac post. Does the exciter wire or the sense wire go to this post? Also, I have no remote engine start. I did see one wire taped off near the alternator. See photo. Perhaps the truck shop in Jackson cut the wire off at this spot.

I think that any post with constant +12vdc straight from the battery (not through a diode) would work for the sense; for me the remote start was the most convenient place to take that from.

Was that taped off wire the smaller red one I can see in that photo? That looks a *lot* like the one that would correspond to the ignition wire that would go to post "B" on the drawing on page 5 of the .pdf file. Easy enough to test... if it goes to +12vdc with the ignition key switch ON then it is probably the right one. Could trace it back to the isolator with a buzzer or an ohmmeter too.

The only wires you need on the Hehr are the four you outlined in this post. Make sure that there are no extra jumpers (E) and (F) on that drawing in the .pdf file.

Not sure what more I can tell you about this. Your automotive technician should be able to understand the instructions for isolator wiring of a Hehr on page 5 of the .pdf and correlate that to the drawing on page 4. That .pdf was what straightened it all out for me.

If you are changing to a different alternator type then I'm not qualified to comment as I have not studied any replacement. I found that just figuring out the original was difficult enough.

Craig

Re: Alternator

Reply #17 – July 16, 2012, 12:07:34 pm

Changing to a correct 4 wire alternator is one option (after locating a 12V source that is on/off with the ignition. The other option is to keep the one I have but I have to be able to acceptably excite the output post to get it going. In Jackson they accomplished this by jumping the sense line but this means that when the engine is stopped the 12V from the battery side of the isolator is still being fed back into the center post and distributed to the house side too thus defeating the isolator. The jumper would be fine if there was something inline to allow the voltage to travel in one direction only. When the engine is stopped there is 12V on that line but very low amperage so I wouldn't think I'd need much of a diode to accomplish this goal but when the engine is running there will be very high amperage on this line. Will it just overcome the diode or destroy it thus necessitating a very substantial diode in that line? I'm sure the auto electric guy will know.

Re: Alternator

Reply #18 – July 16, 2012, 12:10:47 pm

Sometimes it is alot cheaper to take the issue to a proper shop to solve the mystrey before the smoke jumps out of the wiring.
FWIW
Dave M

Re: Alternator

Reply #19 – July 16, 2012, 06:15:43 pm

If this is the case, and the tech service knew what he was talking about, Delco's claim that this alternator will directly substitute for DUVAC is wrong. Might be time to follow Dave M's advice before you let the magic smoke out.

Re: Alternator

Reply #20 – July 16, 2012, 07:19:05 pm

The magic smoke,once you let it out,it is ex pensive to put it back in.

Re: Alternator

Reply #21 – July 16, 2012, 07:22:27 pm

It has been running for two years with the output post jumped to the sense post (thereby getting 12V from engine side of isolator to excite the output post). Neither the truck shop, Delco or the auto electric guy have gotten to excited about this. The problem is that this ties the two batteries together (like the boost switch) when the engine is off (or on, but the isolator does that normally when the engine is running charging both batteries). I'm considering finding a wire that has 12V when the ignition is on and running it to a solenoid (like the boost switch) which will be wired to the two posts in question. That way when the ignition is on the switch will allow the engine battery 12V off the sense wire to excite the output post (just as it has been doing) but will be off when the ignition is off. When it is time for a new alternator, I'll have 12V off the ignition handy for the forth wire in the typical Foretravel alternator arrangement. Barry has instructions on his site for doing surgery to an off the shelf alternator to turn it into a four post one but this more than I want to get into.

Re: Alternator

Reply #22 – July 16, 2012, 07:39:48 pm

Forgot to add that since the excite to the output post only needs to be about 7.5 volts, I will use wire equal in gauge to the wire on the output post to make my run to the solenoid. I think the big concern with the present arrangement is that the tiny wire jumping from the output post to the sense post and the sense wire to the engine side of the isolator is smaller than the wire on output post...which is probably asking for the magic smoke.

Re: Alternator

Reply #23 – July 16, 2012, 08:09:12 pm

Quote from: Dwayne – July 16, 2012, 07:39:48 pm

Forgot to add that since the excite to the output post only needs to be about 7.5 volts, I will use wire equal in gauge to the wire on the output post to make my run to the solenoid. I think the big concern with the present arrangement is that the tiny wire jumping from the output post to the sense post and the sense wire to the engine side of the isolator is smaller than the wire on output post...which is probably asking for the magic smoke.

Make sure you document what you've done for future owners of your U240. I'm keeping mine stock until I can arrange a system that is better than the alternator/regulator system used now. It's not a cheap upgrade (like the Progressive Industries charger/converter is) but I think it's worth working towards. More important if you drive a lot; less important if you spend more time plugged in or on solar.

Craig

Re: Alternator

Reply #24 – July 17, 2012, 11:34:24 am

Just maybe that sense wire is more than a excite tap, I have not looked at the actual connections on YOUR setup, but MINE uses that terminal for reference voltage in addition to exciter. SO when I read your comment about only needing 7.5 VDC at the sense terminal, I would expect and hope the actual output of the alternator will try get the sense voltage up to the 14.1 or where ever it is calibrated to. This will do a few things not really wanted, over charge batteries and kill the alternator.
Not knowing nor understanding and playing with different possibilities makes me feel you have a lot more money to throw around than most are willing to.
Guessing can get real costly and dangerous.
Good luck
Cheers
Dave M

Affiliate Notice