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Mark Patrick
Mark Patrick,
Category: Medium and Heavy Trucks
Satisfied Customers: 6
Experience:  Head Mechanic at Estill Wood Products
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I have a Vnl 610 semi truck the blower. The cab blower works

Customer Question

I have a Vnl 610 semi truck the blower. The cab blower works on 1,2,and 3 but not on 4
Submitted: 1 year ago.
Category: Medium and Heavy Trucks
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!

Blower motor resistor is bad. Replace the resistor to resolve this issue.


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.

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Expert:  Jeremy replied 1 year ago.

The other it could be is the blower motor fan speed high relay. It is in the fuse box. Swap it with the wiper for testing and see if you have a bad relay. If that doesn't solve, then replace the resistor.

Expert:  Jeremy replied 1 year ago.

I can't do a phone call right now, but the request is open to other experts who can.

Customer: replied 1 year ago.
I changed the resistor That mounted in blower casting the blower the switch
Expert:  Jeremy replied 1 year ago.

You did the resisotr and there is no change? And the switch? What about the high speed blower relay? That relay only operates the number 4 blower speed.

Customer: replied 1 year ago.
Where is it located cause the Volvo truck doesn't have a high speed relay like Freightliner or kW
Expert:  Jeremy replied 1 year ago.

what year is the Volvo?

Expert:  Jeremy replied 1 year ago.

you're right. Everything on that is throgu the climate control unit and the blower control unit. It is all computerized.

I was just assisting with a Columbia and got you two mixed up.

Do you have a code on the dash for the A/C failing? On these, you have to use the PTT software to clear the codes out when you lose functions. The head unit is most likely faulting internally on this. I doubt it is the climate control unit.

If you want to do some pin tests, CLICK HERE for the diagram on this model

Customer: replied 1 year ago.
The ac works fine . Jus tha that the blower won't work on high 4
Expert:  Jeremy replied 1 year ago.

You replaced the head unit where the control switch is?

This system is all computerized where it works off the signal from the head unit to the A/C control module, to the blower control module for the fan speed operation. You have the signal between them so you have either a fault in the head unit, the control module (which you did so that is ruled out), or there is a code that is stopping the high speed operation to prevent overheating of the blower. Only PTT can clear that. It's aggravating, but that is Volvo engineering.

Expert:  Jeremy replied 1 year ago.

On the back of the control unit. You have a plug there. See if you have power coming out of pin 10, wire 676. That is the power wire for the steppr motor number 4. That is what gives you the 4th speed. If you have no power, that control unit is bad.

CLICK HERE for pin chart

CLICK HERE for plug location

CLICK HERE for wire number

Customer: replied 1 year ago.
My truck is a 1999 Volvo Vnl 610
N794054 vin last 6
Expert:  Jeremy replied 1 year ago.

Yep, diagram still matches and is the same.

Customer: replied 1 year ago.
Doesn't look like my truck
My truck has one knob
Expert:  Jeremy replied 1 year ago.

The plug is the concern, not the knob. Did you test the wire?

Expert:  Jeremy replied 1 year ago.

How are you coming along on this?

Customer: replied 1 year ago.
There's power in all holes on switch
Nothing still don't work
Expert:  Jeremy replied 1 year ago.

Did you check the wire going to the blower at the back of the switch, then again at the blower? If so, then you need to see if there is a programming issue on the module.

Customer: replied 1 year ago.
there's power
Expert:  Jeremy replied 1 year ago.

If you have power, then there is a program issue. The module needs to be programmed and you will need PTT with Volvo access to do that.

Customer: replied 1 year ago.
Wats that
Expert:  Jeremy replied 1 year ago.

Volvo PTT is the software program to program the module. It is what Volvo uses for all programming and diagnosing.


Customer: replied 1 year ago.
You trying to charge me $120 for what exactly
My shit still don't work
Is you crazy
Expert:  Jeremy replied 1 year ago.

Huh? Let me give some explanations below to assist you...

#1, I don't charge anything. I have no control over that at all so I don;t know what you are writing about.

#2, customer service is who handles all of that. I ask that you contact them instead of using the language you have with me. I will also send a message to customer service for you so that they can assist you.

#3, you haven't followed up with me after the need for the programming of the module. Were you able to do that, yet?

#4, I have assisted you for several days paying out of my pocket to provide you with needed diagrams and where to check for power on this issue. I also informed you of the next steps to follow. I have not been given a rating so I have not received a penny for my time. Due to this, after sending the request for customer assistance to assist you, I am opting out for it would appear you are either unable to do the needed follow ups for diagnosis due to not having the equipment or the inability to do the checks due to not having the needed testers. I would suggest at this time that this be taken to a shop that has the ability to do this repair for you.

Good luck to you on this repair and good day!

Expert:  Mark Patrick replied 1 year ago.
I would recommend checking the resistor.
Expert:  Mark Patrick replied 1 year ago.
My apologies, I did not see any other comments. Give me a few to read through.