Alternator P1105
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Tuned
Joined: Jan 2023
Posts: 396
Likes: 171
Alternator P1105
Getting a P1105 for upper alternator. Looking for some 7.3 experienced knowledge.
Charge light comes on koeo, running goes out. Output of the alt 13.5 no load, 12ish under load, slowly lowers.
I would call the alt, but the light green/red wire is showing 10.5v unplugged, 8v plugged in and running (the other wire is battery voltage, alt B+ is battery voltage). I believe this should show battery voltage. If I jump 12v (through a test light) to this wire while running, under load the output jumps to low 14 volt and stays in that range after removing the jumper.
the lower alt appears to not be working, but no code.
I am thinking resistance on the light green/red circuit. Was going to start by disconnecting the lower alt and test there.
Am I missing something? Ideas where to start? Am I just wrong and 10v is normal on this?
edit to add through a test light
Charge light comes on koeo, running goes out. Output of the alt 13.5 no load, 12ish under load, slowly lowers.
I would call the alt, but the light green/red wire is showing 10.5v unplugged, 8v plugged in and running (the other wire is battery voltage, alt B+ is battery voltage). I believe this should show battery voltage. If I jump 12v (through a test light) to this wire while running, under load the output jumps to low 14 volt and stays in that range after removing the jumper.
the lower alt appears to not be working, but no code.
I am thinking resistance on the light green/red circuit. Was going to start by disconnecting the lower alt and test there.
Am I missing something? Ideas where to start? Am I just wrong and 10v is normal on this?
edit to add through a test light
Laughing Gas
Joined: Jun 2013
Posts: 1,094
Likes: 514
From: Yokosuka Japan
Getting a P1105 for upper alternator. Looking for some 7.3 experienced knowledge.
Charge light comes on koeo, running goes out. Output of the alt 13.5 no load, 12ish under load, slowly lowers.
I would call the alt, but the light green/red wire is showing 10.5v unplugged, 8v plugged in and running (the other wire is battery voltage, alt B+ is battery voltage). I believe this should show battery voltage. If I jump 12v (through a test light) to this wire while running, under load the output jumps to low 14 volt and stays in that range after removing the jumper.
the lower alt appears to not be working, but no code.
I am thinking resistance on the light green/red circuit. Was going to start by disconnecting the lower alt and test there.
Am I missing something? Ideas where to start? Am I just wrong and 10v is normal on this?
edit to add through a test light
Charge light comes on koeo, running goes out. Output of the alt 13.5 no load, 12ish under load, slowly lowers.
I would call the alt, but the light green/red wire is showing 10.5v unplugged, 8v plugged in and running (the other wire is battery voltage, alt B+ is battery voltage). I believe this should show battery voltage. If I jump 12v (through a test light) to this wire while running, under load the output jumps to low 14 volt and stays in that range after removing the jumper.
the lower alt appears to not be working, but no code.
I am thinking resistance on the light green/red circuit. Was going to start by disconnecting the lower alt and test there.
Am I missing something? Ideas where to start? Am I just wrong and 10v is normal on this?
edit to add through a test light
I am not a trained mechanic, these are just my observations and experiences since I first turned a wrench in 79 on the farms tractors and trucks.
Ken
Last edited by kenn_chan; Apr 11, 2023 at 05:05 AM. Reason: screwup in verbiage
Thread Starter
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Tuned
Joined: Jan 2023
Posts: 396
Likes: 171
Thanks for the replies,
that answers the question, the light green/red should be over 12v .
Now the fun starts. Have not gone to far on it, so far the fuse is showing system voltage.
Most likely won't get a chance to look at it for a few days, so I figured I would ask you all.
I wish I knew what was going on inside the pcm, my first move will be disconnect and check at the plug near the vacuum pump.
I will update everyone on what I find.
that answers the question, the light green/red should be over 12v .
Now the fun starts. Have not gone to far on it, so far the fuse is showing system voltage.
Most likely won't get a chance to look at it for a few days, so I figured I would ask you all.
I wish I knew what was going on inside the pcm, my first move will be disconnect and check at the plug near the vacuum pump.
I will update everyone on what I find.
Thread Starter
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Tuned
Joined: Jan 2023
Posts: 396
Likes: 171
Had about an hour yesterday. Thought about going after the pcm connector, but didn't think I had enough time.
I was curious if the lower alt was working so I pulled the fuse for the upper. Instantly charged over 14v.
So, then I checked only the upper. Over 14v..
Put both fuses in, 13.3v...
This is saying to me (without knowing internal pcm routing) a supply issue to the pcm.
I decided to pull the cluster, back probe the connector on the cluster and had system voltage. Then I noticed the truck was charging at 14.4. At the alt I wire I have 1 more volt than before.
Ran out of time, but I will be pulling the cluster and checking wires behind it.
I was curious if the lower alt was working so I pulled the fuse for the upper. Instantly charged over 14v.
So, then I checked only the upper. Over 14v..
Put both fuses in, 13.3v...
This is saying to me (without knowing internal pcm routing) a supply issue to the pcm.
I decided to pull the cluster, back probe the connector on the cluster and had system voltage. Then I noticed the truck was charging at 14.4. At the alt I wire I have 1 more volt than before.
Ran out of time, but I will be pulling the cluster and checking wires behind it.
FTE Leadership Emeritus
Joined: May 2014
Posts: 27,348
Likes: 5,941
From: Lake Hartwell, GA
Could be a corrosion or poor continuity issue. I had one like that recently that "disabled" my turn signals. A bit of 800 grit sand paper and some DeOxIt spray and all is well. A pencil eraser sometimes works well on ribbon cable style contacts like in the back of the instrument cluster I have.
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Tuned
Joined: Jan 2023
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Thanks, that is also my thinking.
Finding these things is frustrating. That's mostly why I am putting the steps I am taking here, and not just finding it and telling what the problem was.
maybe someone can take away something from it. Maybe someone can say where I went wrong. When you are in the middle of doing it frustration can take over pretty easily.
I could just pull a fuse and drive with one.... For now.
Finding these things is frustrating. That's mostly why I am putting the steps I am taking here, and not just finding it and telling what the problem was.
maybe someone can take away something from it. Maybe someone can say where I went wrong. When you are in the middle of doing it frustration can take over pretty easily.
I could just pull a fuse and drive with one.... For now.
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Thread Starter
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Tuned
Joined: Jan 2023
Posts: 396
Likes: 171
Putting this on the back burner for now.
where I am at
Bad connection at the cluster, fixed.
Alternator is getting 11.5v on the I wire.
System is charging normal.
Need to check pcm connection.
Question,
Can someone with a dual alternator truck do me a favor and test volts on the green/red wire on the upper alternator? Disconnected key on engine engine off.
where I am at
Bad connection at the cluster, fixed.
Alternator is getting 11.5v on the I wire.
System is charging normal.
Need to check pcm connection.
Question,
Can someone with a dual alternator truck do me a favor and test volts on the green/red wire on the upper alternator? Disconnected key on engine engine off.
Thread Starter
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Tuned
Joined: Jan 2023
Posts: 396
Likes: 171
The other thing I noticed is it will not go over 12v, or under until the glow plugs shut off. It seems Like the pcm is controlling it, when the glow plugs shut off charging goes from exactly 12v to around 14.4
Laughing Gas
Joined: Jun 2013
Posts: 1,094
Likes: 514
From: Yokosuka Japan
S-squatch,
the PCM keeps the one alternator shut off until the glowplugs shut off, this is to keep them from raising the voltage too high and causing failure of the glow plugs themselves. this was documented in this thread : https://www.ford-trucks.com/forums/1...get-along.html its along read but if you read it it explains about how the PCM controls the dual alternators, and explains why your truck comes with dual 110 amp alternators vice just one large high output.
the PCM keeps the one alternator shut off until the glowplugs shut off, this is to keep them from raising the voltage too high and causing failure of the glow plugs themselves. this was documented in this thread : https://www.ford-trucks.com/forums/1...get-along.html its along read but if you read it it explains about how the PCM controls the dual alternators, and explains why your truck comes with dual 110 amp alternators vice just one large high output.
Got Data?
Joined: Dec 2012
Posts: 4,245
Likes: 1,375
From: Lake Stevens, WA
I still get P1105 for the upper alternator from time to time, but appears to be working fine from my measurements. I'm going to call it a 'ghost' code at this point.
These OEM alternators don't put out much more than 40-50A at idle. Right after starting, only the upper alternator is putting out - the lower one commanded off by the PCM, and the voltage will be a bit low, ~12V or so while the glow plugs are on. My batteries are pretty tired 6 year old lead acid units, and this is typical for me. Those GPs are drawing 100A plus and so the one alternator is not going to keep up with that - just partially replenishing the batteries - so the voltage stays low. Like kenn_chan mentioned, after the GPs go off, the PCM kicks in the lower alt, and you see ~14V. I'd say your rig is working fine.
These OEM alternators don't put out much more than 40-50A at idle. Right after starting, only the upper alternator is putting out - the lower one commanded off by the PCM, and the voltage will be a bit low, ~12V or so while the glow plugs are on. My batteries are pretty tired 6 year old lead acid units, and this is typical for me. Those GPs are drawing 100A plus and so the one alternator is not going to keep up with that - just partially replenishing the batteries - so the voltage stays low. Like kenn_chan mentioned, after the GPs go off, the PCM kicks in the lower alt, and you see ~14V. I'd say your rig is working fine.