2nd Gen Non-Engine/Transmission Electrical Gremlins

[spacecadet]

Driving through the hot SW desert last month, our 01 Quad cab had electrical issues. Three times in one hour the cruise control disengaged while driving on the interstate and at the same time the AC went into defrost mode, meaning all air went to windshield and I think fan went to high. This lasted about 15 minutes and then everything returned to normal. Happened several times over the next few hours, but did not recur for the rest of the 1000 mile trip.

We had a problem with the fuse box several years ago where the engine would suddenly die. Pretty scarey at traffic lights. Fortunately it would start right up again. Dealer found corrosion on some fuse box contacts, and cleaning everthing has prevented a recurrence. Apparently this is a known problem. Could this latest problem have the same cause as the earlier one? I thought they cleaned everything at that time. Where do I start with this?

 

[petersonj]

hree times in one hour the cruise control disengaged while driving on the interstate and at the same time the AC went into defrost mode, meaning all air went to windshield and I think fan went to high.

Your cruise control is vacuum operated and your HVAC system uses mostly vacuum motors on the ventilation doors. If vacuum supply is lost at the HVAC, then airflow to the defroster becomes default. The cruise control would also stop working.

I would go to the engine compartment and begin inspecting vacuum lines and connections starting at the vacuum pump. With the age of your truck, I would suspect that many of your vacuum lines are in poor condition.

- John

 

[spacecadet]

Your cruise control is vacuum operated and your HVAC system uses mostly vacuum motors on the ventilation doors. If vacuum supply is lost at the HVAC, then airflow to the defroster becomes default. The cruise control would also stop working.

I would go to the engine compartment and begin inspecting vacuum lines and connections starting at the vacuum pump. With the age of your truck, I would suspect that many of your vacuum lines are in poor condition.

- John

Your cruise control is vacuum operated and your HVAC system uses mostly vacuum motors on the ventilation doors. If vacuum supply is lost at the HVAC, then airflow to the defroster becomes default. The cruise control would also stop working.

I would go to the engine compartment and begin inspecting vacuum lines and connections starting at the vacuum pump. With the age of your truck, I would suspect that many of your vacuum lines are in poor condition.

- John

Thanks for your guidance on this John. When we were driiving and the cruise and A/C both acted up, I couldn't imagine how those two systems could be connected. TDR is an amazing resource that has saved me more than a few trips to the dealer.

 

[BigPapa]

Check the rubber elbow on the vacuum pump. It may be cracked or swelled up and won’t seal when it gets hot. You can replace it with a Dorman 47092. I know O’Reilly’s has them for less than $10. The hard plastic lines will break if you look at them hard. You can use air brake tubing to replace it and vacuum hose to splice them.