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Jeremy, Certified Truck/Bus Technician
Category: Medium and Heavy Trucks
Satisfied Customers: 3304
Experience:  ASE Med/HD Truck Technician, NATEF Diesel Engines and Electrical/Electronics Technician, EPA 608/609 HVAC Certified, Steering/Suspension and ABS/Brakes Technician
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2009 Volvo VNL 630, Cummins ISX. Have an issue with erratic

Customer Question

2009 Volvo VNL 630, Cummins ISX. Have an issue with erratic power. Just driving along the power at times will drop 1 volt for no apparent reason. The diagnostic for the engine has a fault for erratic power. At times when the brakes are pressed or turn signal is activated or when the high beams are activated the dash lights will flash for a nano second. Today pulled up the fuel pump, cut the truck off then it would not start. I tried a few times with nothing from the starter. The dash check was fine. Volts was at 12.4 per the guage. I left the turn on and started the truck from the solenoid. It starts just fine now. Do these trucks have some type of power supply unit that controls and distributes power?
Submitted: 1 year ago.
Category: Medium and Heavy Trucks
Expert:  Jeremy replied 1 year ago.

My name is ***** ***** I will assist you today.

Please give me a couple minutes to sign into your vehicle information and I will be right with you.

Expert:  Jeremy replied 1 year ago.

My name is ***** ***** I will assist you with your question today.

I'm an independent contractor and I don't get paid until a rating has been made.

We can go back and forth as needed to help resolve the issue you are having. Follow ups are free after ratings, so rate in confidence!

The voltage control goes through the cluster. These trucks have a bad issue of building corrosion on the plugs in the back of the cluster. I would pull those plugs and clean them with electrical contact cleaner (you can buy the can for $6.99 at any auto parts store) and let them dry for about 5 minutes, then plug them back in. See what it does after. If the issue continues, have the cluster tested with the PTT program. If these clusters lose power, they will keep the truck from starting. The starter signal comes from the Vehicle Control Module and if it can't see the cluster, it will not start the truck.

I believe the 2 issues you have are related to the one issue in the cluster. Your starting and your voltage are both affected by the cluster. Otherwise, there are no other modules in place.


You want a 5 star service and I want to provide a 5 star service. Please consider that I don't know your skill level as well as I can't see, touch, smell, hear the vehicle/machine in question. Please provide as much detail as possible and I will provide as much back.

Once an answer is provided, you should see a rating screen. Please rate my personal service to you. The ratings are my personal feedback,

they are not the site feedback.

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Customer: replied 1 year ago.
How do I get to the "cluster". I have now idea where it is and how to get to it.
Expert:  Jeremy replied 1 year ago.

The cluster is your instrument panel with the speedometer and the tachometer.

You have screws on the front of the dash and you remove them, pull the cluster forward, and the plugs are right there on the back.

Customer: replied 1 year ago.
Jeremy, your suggestion worked well for one day. I cleaned the back of the display on Saturday. On Monday I drove about 300 miles and the truck performed perfectly. On Tuesday morning, before I started it I noticed when I opened the door the low voltage alarm sounded and the problems came back. On Wednesday morning the problem got worse. When I used my turn signal I actually low power completely. My trailer marker lights went out and would not come back on. I turned around and went back to my yard and tried to diagnose the problem. After about an hour or so, the marker lights just came back on without any apparent help from my. The one problem is the voltage. At the alternator and battery, with everything on, I'm getting about 14 volts. On the display, it will be approx 12 or so. On Tuesday the voltage was erratic, it would drive down to below 10 on the display for a few seconds and then stabilize at 12.5 or so while driving it. Any other suggestions?
Expert:  Jeremy replied 1 year ago.

Check the LVD. It should be in the battery box. Follow the power cables to the relay box in there. Jump the positive cables together bypassing that box and see what it does. If it stabilizes, the LVD is bad.

LVD id is the Low Voltage Disconnect.

Customer: replied 1 year ago.
Thanks, ***** ***** do you have a picture of the lvd?
Expert:  Jeremy replied 1 year ago.

I went through all that I have to find a picture of it and I can't locate one. The manuals don't have one at all.

It is a black square box. The red cable goes right to is. Sometimes they are mounted on the driver side behind the batteries. Other times they are in the box itself. Volvo does move them on their trucks.

Expert:  Jeremy replied 1 year ago.

I see you viewed this and this is still showing as an open question due to no positive (3 stars or more) rating.

Were you not pleased with my service to you or is there a rating issue? Please let me know if you still need assistance with this, if there is a rating issue, and/or you need more time to respond.

I like to make sure all my customers are satisfied since you did pay a deposit for me to assist you, whether I’m paid by a positive rating feedback or not.

We can continue where we left off or start over if needed. Also, if you need diagrams, instructions, etc please don’t hesitate to ask.

Customer: replied 1 year ago.
Hi. Still trying to resolve this issue. Had the truck in the shop for 10 days and they said the cluster was bad. Replaced it, got it reprogrammed and the same issues are still present.Your last suggestion was the low voltage disconnect. The little box on top of the batteries is not connected to a battery. It is a small box that has a battery cable going in and coming out of it with a fuse.Jeremy, I get an fault code sometimes when I'm starting the truck. Check out the attached pictures. I got these on Friday when the trailer wasn't connected to the truck.Jeffrey
Expert:  Jeremy replied 1 year ago.

I'm opting out of this question.

This has gone on for 16 days now and the new information doesn't even coincide with the original complaint. The new question is involving the lighting module where teh original complaint was about a voltage issue. These 2 issues are not related and I feel like this is getting dragged out with no guarantee of payment for the asistance I have already given.

I haven't received any form of payment on this question as it is AND based on the last 3 experts that have assisted you, your history doesn't show a positive note that I will get payment on this one.

I am electing to opt out of this and moving on.

Good luck on your repairs.

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