98 VNL cruise control

[solo318]

I'm in need of a little help on my 98 vnl. The cruise keeps dropping and the jakes quit working at the same time.  The only direct correlation I can think of is the clutch switch, So I replaced it. still doesn't stay engaged. It seems to work for 45 min to an hour, then it quits. if you don't use it for a while it will start working again.  I looked at the schematic and it looks like the clutch switch comes from the ecu and back to it. If any of you guys have any insight I would love to here from you.

It's a 98 vnl42 with a cummins select n14 and a super 10 trans.

[Darryl&Rita]

There's another common point. The brake air line should have 2 pressure switches, one NO for the brake lights, and one NC to tell the ECM to disconnect the cruise.

[Brad & Jacolyn]

When my cruise would not stay engaged it was a switch on the brake pedal. A bump would cause the pedal to move enough to disengage. I used a small bungie cord to hold the pedal up a bit higher and the problem stopped. They adjusted (or replayed I don't remember) and that corrected my problem.

[chief916]

I had the same issue on my 97 Volvo WIA64 about 18 months ago.  Had several technicians look at it and they had everything hooked up to computer and all that.  Finally ended up taking the truck to guys who worked on Detroit diesels only.  They chased it down to a faulty ecu.  They changed it out and I've been back an forth now from California to Sturges to Yellowstone and all places in between.  Runs like a champ.  It cost me $$$$ but it was really worth it.

[rpsinc]

Have you done a cursory check of the grounds??

[solo318]

I've checked all the grounds I can find. I currently have my equipment hooked up to the ecu brake relay.  It hasn't acted up today, and I haven't driven it out on the open road. sitting here everything checks out fine. problem is that when it acts up, I'm running 60 and I can't troubleshoot it.

I'm leaving in 3 weeks for South Dakota and I would prefer it be working.  

 

[Darryl&Rita]

Time to get it out and drive, then. Brad has the right idea, as that model doesn't use a pressure switch, it has a mechanical switch to turn the cruise off. When it cuts out, lift the pedal with your toe. If this prevents a recurrence, look at the switch adjustment, or replacement.

[Chad Heiser]

I'm not sure if the Volvo's are set up like my Kenworth, but when I had issues with my cruise and Jake not engaging or dropping out, it was the Throttle Position Sensor that was going bad.  I replaced the TPS and all was back to normal.

[JPL]

SOLO318   My 98 is exactly like yours and I had some ecm problems. I sent it out to Colorado and had it rebuilt. Cost a 1/3 of a new one. don't have address but can locate if needed.    Pat

 

 

The O;d Sailor

[solo318]

13 hours ago, JPL said:

SOLO318   My 98 is exactly like yours and I had some ecm problems. I sent it out to Colorado and had it rebuilt. Cost a 1/3 of a new one. don't have address but can locate if needed.    Pat

 

 

The O;d Sailor

That would be really helpful.  all of my switch testing comes back good. But they all ground through an ecu circuit. I might try giving it an external ground and see what happens.