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The battery is not charging, and when I use an ohms meter between the alternator output terminal and the battery +, I read 7.5 ohms. When the motor is running I see 14.45v between the alternator terminal and ground. Rather than mess about with wiring looms etc. I would prefer to run a new cable from the alternator to the battery. Are there any issues I should be aware of?

Edit I found the diagrams and there looks to be a fuse needed.

Jeep Patriot 2.0 litre diesel, 2007

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  • Do you have a wiring diagram for the vehicle?
    – HandyHowie
    Commented Mar 28, 2022 at 22:25
  • I found and uploaded the diagrams. Apart from the fuse do you know what the "S150" and the "A801 6 RG/DY" stand for?
    – Owen
    Commented Mar 29, 2022 at 8:06
  • Welcome to Motor Vehicle Maintenance & Repair! What is giving you the indication your battery is not charging? If you are getting 14+VDC out of the alternator, it's doing it's job. What is the voltage at the battery when you're running the engine (positive post to ground)? If it's the same, then maybe its the battery which is at fault?
    – Pᴀᴜʟsᴛᴇʀ2 ♦
    Commented Mar 29, 2022 at 12:13
  • @Paulster2. It's a new battery and my DMM shows it's not charging even though the alternator is outputting at 14.45v. Looks like too much resistance in the wire.
    – Owen
    Commented Mar 29, 2022 at 16:45
  • Why are you quoting ohms in one sentence and comparing it to volts in the next? Sure you can convert, but you can't compare them directly.
    – FreeMan
    Commented Mar 30, 2022 at 18:24

2 Answers 2

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You can run a bypass wire with these precautions:

The wire gauge must be the same size or larger than the old wire. The old ends must be cut so that the orphaned wire is not connected to anything. The new wire should follow a safe pathway and be secured properly. The new connections must be crimped or soldered properly.

Before you do that:

The old wire probably has resistance at one or both ends. Repairing the end connections could be a better solution. You could measure the resistance of the actual old wire by piercing the wire close to but away from each end. This will tell you if the problem is the wire itself or just the end connections.

These are general tips for installing a bypass wire, only if it has no intermediate connections and only if there is no fusible link in that wire.

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    What are you quoting?
    – GdD
    Commented Mar 29, 2022 at 8:03
  • I think you need to examine the wiring diagram that has been added and alter your answer.
    – HandyHowie
    Commented Mar 29, 2022 at 10:42
  • I'm marking this as the correct answer. In the end I did not go the route of a bypass wire because I found the bad connection. But you answered the question I asked.
    – Owen
    Commented Mar 30, 2022 at 22:21
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I wouldn’t do that.

If you look at the wiring diagram, it looks like the alternator is connected to the starter motor terminal.

Presumably the starter works correctly, so the issue can’t be between the battery and the starter motor.

I would check the resistance between the starter and the alternator first, then try to identify the issue. Maybe the connections just need cleaning.

As you point out, there is a fusible link involved in this connection. Maybe the fault is with the connections to the fusible link.

If you decide to replace the wire, just replace the section from the alternator to the starter motor with an identical wire with the fusible link.

The RD/GY (I presume you have just typed yours incorrectly) will be the colour of the wire’s insulation - likely RED and GREY.

The S150 could be a connector, with the drawing showing the position. S150 is definitely a place to check.

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    S150: S denotes a splice. Definitely one of the places to look.
    – Jupiter
    Commented Mar 29, 2022 at 13:18
  • From looking at youtube video you pretty much need to take out the starter motor to remove the wire that is connected to it. Just looking for an easier fix.
    – Owen
    Commented Mar 29, 2022 at 15:25
  • @Owen add a link to the video
    – HandyHowie
    Commented Mar 29, 2022 at 15:34
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    @HandyHowie - Yes I worked on the car tonight and I have more access on my model. I removed the battery bay and had decent access to the starter. I unhooked the cable from the starter to the alternator and my DMM showed 0.0 ohms now, which means (probably) it had a bad connection there on the starter. Tomorrow I will clean those connections and reconnect. Hopefully I'll get some battery charging tomorrow!
    – Owen
    Commented Mar 29, 2022 at 22:17
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    @Owen. Good new.
    – HandyHowie
    Commented Mar 30, 2022 at 22:31

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