I was referring to that also... except I started the reference...
Actually it was not gambling... it was a game show...

Hello oilslick
Simple test. Re: aux. pump
#1. Get car to operating temp.
#2. Set defrost and max heat.
#3. Feel hose on each side of pump. (note hot/cold)
#4. Feel hose on each side of mono valve. (note hot/cold)
Please post results.
I second the infrared thermometer guns available today.
Good accuracy and no risk of injury while trying to get awkward temp areas.
The heat on one side only sounds like blend door vacuum motor failure or broken hose.
Have a great day.

__________________
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Prototype R&D/testing:
Thermal & Aerodynamic System Engineering (TASE) Senior vehicle instrumentation technician.
Noise Vibration and Harshness (NVH).
Dynamometer.
Heat exchanger durability.
HV-A/C Climate Control.
Vehicle build.
Fleet Durability
Technical Quality Auditor.
Automotive Technical Writer

1985 300SD
1983 300D
1984 190D
2003 Volvo V70
2002 Honda Civic

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Headed back to church for evening service.

Leathermang,
I hear ya!

Kevin

I was thinking about the 123 car for the location of the aux pump. Check the temps around throughout the system.

__________________
Jim

that it's the T-stat. I am going to replace it in the morning. I feel confident that if I can get the engine temp up to normal that my heat system will be fine.

Kevin

Hello Kevin
The climate control system starts putting out heat at 25C too 30C.
I can get my 1985 300SD to begin heating at 25C and my engine temperature climbs fast to 40C.
When my engine temp hits 40C; it will cook you out of the car on max.
What you need to understand; is that this system is not like any domestic vehicle.
The climate control system is totally independent of the engine; there is no water pump bypass hose feeding the heater, the heater pump draws and returns directly from and to the engine cooling jacket.
The Temp sender is in many cases more important to the climate control system start time than the thermostat is.

Possible causes for your issue:
#1. Temp sender bad.
#2. Mono valve bad.
#3. Heater pump bad.
#4. Controls problem, wrong air blend doors opening.
#5. Heater core plugged up.

Follow all safety precautions for torch use, gloves, safety glasses, etc.
To test the temp sender:
Remove it, reconnect the wire, run a ground wire to the metal of the sensor, hold the sensor with insulated pliers as it will get hot, turn the key to run, (DO NOT CRANK ENGINE), use a lighter or propane torch on low to warm (not burn) the tip of the metal tip of the sensor while someone watches the gauge, the gauge should hit 90C in under 30 seconds average.
If it fails to come up fast, replace the sender unit, it is bad.

Ok; here comes the legal stuff.
If you choose to attempt this; you assume full responsibility for your own actions.
I have written this as an FYI, not a technical how to.

I get good 140*f heat from all vents when the engine is at 80*c. I know the aux pump is not working. I removed it, applied 12v to it and nothing happened.

Would it be worth taking it off and rebuilding it?

How many temp senders are there on a 300SD Turbo engine? I removed the wire to a temp sender(rearward) and the gauge quit but there is another thingamajig (forward) on the head that looks identical to the other sending unit but when I remove the wire from it NOTHING happens. I assume that it is not a temp sending unit? If not what is it? Are there two sending units on the head? Huh? Tell me please!

Kevin

It is very likely that your system has an engine temp sensor which activates the aux fan in front of the radiator.... it may also be activated by the pressure switch or temp switch ( too early in the morning to remember off hand) off the Reciver/Dryer....

I replaced the T-stat and viola! It is fixed! Normal operating temps and heat hot enough to toast your toes.

yee ha!

Kevin

Thanks to all who offer their advice. Much obliged!

Hello oilslick

There are two, one for gauge and one for computer.
RE: How many temp senders are there on a 300SD Turbo engine?