OK, I'm driving along, engine warmed up, with heat pouring out of the the dash or floor vents. I set the cruise control to a speed, and within minutes, the heat output drops off significantly, followed by complaints from my wife. When I hit cancel on the cruise control, the heat slowly comes back, and the complaints stop. I know it sounds crazy, but I have observed this for several years. Any ideas? It is not my imagination.
Bill Schlaudecker
2000 U270
Is the question, "How to fix my heater," or "How to stop my wife's complaints?" (Running and Ducking.... ;o)
Does the volume of air coming out decrease, or just the temp of the air?
Bill,
Can you tell us if the volume of air from the vents stays the same or is reduced with the cruise control engaged? Also, in the winter, it may be advisable to close the "motoraid" valve to the hot water heater to increase the output of hot fluid to the heater core. [Caveat: assumes you have a hot water heater and not an Aquahot.]
Need to determine what is common between the cruise and heater. I would bet it is vacuum.
The airflow from the vents does not change. Just the temp drop. I do have the hot water valve closed. When I have cruise control not set to a speed, my heat output is quite good.
Bill Schlaudecker
2000 U270
Bill,
You got me thinking, so, since I was on the road today I did some playing with switches...now, I am really comfused. No air running on dash, temp setting as low as it will go....THEN, when I use the retarter, temperature goes way up. So much so the only way to lower it is to RAISE the lowest cool setting to mid way..then everything is fine again.....and no, I am not making this up. Happens every time. :-\ ::)
I'm not sure but, Jeff, in your case I can see this happening as when the retarder is engaged, all the energy it's absorbing is being transfered to the trans fluid which gets cooled in the same area as the coolant. It could then be raising the coolant temperarure and thus providing you with all that extra boost of dash heat.
When the retarder is activated, cruise is automatically disconnected so there is that common element. But I can't make a connection to the heater.
Bill Schlaudecker
Bill, I can't imagine how your condition is created. Is your dash heater control managed electrically , or is it a mechanical wire type control? If it's electronically contolled, then start looking where these wires (cruise & heater) meet.
From my experience if Bill's heating valve is electrical, there is a bad ground either to the heating switch or cruise control. Now the fun part, finding it. If the valve is not electrical, well then I have no idea.
Don't they both use the same 12 volt vacuum pump?
Check and see if the heat starts coming out of the defroster vents. It has to go somewhere and the default for no vacuum is the defroster vent. IT may be partially closing and going up not towards you.