STD Maintenance General Coolant temp sensors

Coolant temp sensors

Coolant temp sensors

 
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Gasoline Fumes
Diesel Fumes?

54
03-28-2009, 12:28 AM #1
What do the four sensors do on my '85 300D? I see two on the head between the GPs and two in the thermostat housing.
Gasoline Fumes
03-28-2009, 12:28 AM #1

What do the four sensors do on my '85 300D? I see two on the head between the GPs and two in the thermostat housing.

ForcedInduction
Banned

3,628
03-28-2009, 01:00 AM #2
Head: Cluster gauge, glowplug relay
T-Stat: Heater lockout and EGR computer input.
This post was last modified: 03-28-2009, 01:00 AM by ForcedInduction.
ForcedInduction
03-28-2009, 01:00 AM #2

Head: Cluster gauge, glowplug relay
T-Stat: Heater lockout and EGR computer input.

Gasoline Fumes
Diesel Fumes?

54
03-28-2009, 08:03 AM #3
Thanks! Smile
What does the heater lockout do?
Gasoline Fumes
03-28-2009, 08:03 AM #3

Thanks! Smile
What does the heater lockout do?

ForcedInduction
Banned

3,628
03-28-2009, 12:27 PM #4
It prevents the occupants from being blasted with cold air. The switch closes when the engine gets above 40*C.
ForcedInduction
03-28-2009, 12:27 PM #4

It prevents the occupants from being blasted with cold air. The switch closes when the engine gets above 40*C.

Gasoline Fumes
Diesel Fumes?

54
03-29-2009, 03:04 AM #5
Good to know, thanks.
Gasoline Fumes
03-29-2009, 03:04 AM #5

Good to know, thanks.

Gasoline Fumes
Diesel Fumes?

54
03-31-2009, 03:15 AM #6
Now that I've got the sensors sorted out, it's time to put some of my new knowledge to work. I'm trying to fix a couple of issues on my neighbor's '84 300D. I'm not sure if the two are related or not.

1. Temp gauge isn't working. It happened at least once before, but fixed itself. It seems permanently dead this time. Sender is about 764 ohms cold and 98 ohms hot. I tried grounding the sender wire and turning the key on, no response from the gauge. Is the sender connected directly to the gauge?

2. Low heat output. Engine gets hot, heat exchangers (WVO blending) in parallel with heater core get hot. Heater hoses are only warm. What is the default position of the monovalve? Anything else that can limit heater flow? I have a valve in the heat exchanger circuit and closing it has no effect.

I believe the engine is getting up to operating temp.
Gasoline Fumes
03-31-2009, 03:15 AM #6

Now that I've got the sensors sorted out, it's time to put some of my new knowledge to work. I'm trying to fix a couple of issues on my neighbor's '84 300D. I'm not sure if the two are related or not.

1. Temp gauge isn't working. It happened at least once before, but fixed itself. It seems permanently dead this time. Sender is about 764 ohms cold and 98 ohms hot. I tried grounding the sender wire and turning the key on, no response from the gauge. Is the sender connected directly to the gauge?

2. Low heat output. Engine gets hot, heat exchangers (WVO blending) in parallel with heater core get hot. Heater hoses are only warm. What is the default position of the monovalve? Anything else that can limit heater flow? I have a valve in the heat exchanger circuit and closing it has no effect.

I believe the engine is getting up to operating temp.

 
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