AC Heater Harness MOD - How do you Test the TIME DELAY RELAY

[john108]

Hi
I took the Dash Assembly apart years ago and thought I marked all connections.
I am trying to compare new M&H harnesses to original harness and had some confusion.
The picture shows the AC Heater harness, after I disconnected it from the entire Dash Assembly Harness (which came out as a single harness).

Do you know where the 2 connectors, CIRCLED IN RED, attach?
Thank you,
John

[WHITE AND RED 69]

They connect to a control box on the bottom of the a/c box

[john108]

Thankyou WHITE AND RED 69.
My '68 heater box looks like yours.
I guess I didn't attach that component yet.
Is there a preferred location for each wire, One wire is Blue and the other is Brown?
I HOPE the wiring diagram or pictures I took show it.

[WHITE AND RED 69]

I just stole that photo from ebay but I can check mine in the car to see which wire goes which terminal. But I'm pretty sure the blue wire goes to the terminal closest to the seat?

[john108]

The attached picture is from my Service Manual.  I am interpreting the BL and BR wires relative to their positions to the 45 degree chamfer and small circles.
The service manual picture appears to be looking from the back of the part or a mirror image if it.
I seem to notice places where the service manual doesn't match the real parts.

[john108]

How do you Test the TIME DELAY RELAY.  Two Pictures Shown Above.

[Bronzedodge]

Ok, it actually doesn't matter which wire go on the time delay relay terminals.  It's just a SPST switch, doesn't reference ground.  The test is that the compressor clutch will engage - A/C on - for 1 to 10 minutes, and the heat or defrost buttons are selected, if the interior is above approx 25 deg F.  If you're super cold, no A/C.  The purpose is to reduce fogging/condensation on the windshield, i.e., dry, dehumidified air.  FSM page 24-10 in '69 book

Mine had started to hang up - running the A/C longer that 10 minutes on a cool day with the heat on.

[Nacho-RT74]

can I ask what's the function of the Time delay on this sistem AND, why later cars didn't got it?

[Nacho-RT74]

The test is that the compressor clutch will engage - A/C on - for 1 to 10 minutes, and the heat or defrost buttons are selected, if the interior is above approx 25 deg F.  If you're super cold, no A/C.  The purpose is to reduce fogging/condensation on the windshield, i.e., dry, dehumidified air.  FSM page 24-10 in '69 book

Mine had started to hang up - running the A/C longer that 10 minutes on a cool day with the heat on.

I guess here is a partiall answer, but still don't get it

[Bronzedodge]

The first thing ANY good A/C system does is dehumidify the air.  The engineers wanted to avoid starting the car on a humid fall day and having the system fog up the inside of the windshield for a minute before the heater core warmed up.  They were thinking of dewpoints and such.

In actuality, the temp/humidity conditions for excessive fogging on the inside of the glass usually do not last long.  I think maybe they wanted to keep compressor oil freshly splashed on the shaft seal during the winter months to slow/avoid leakage of refrigerant.  Bottom line is the compressor runs 10 minutes max when you run Heat or Defrost during the winter.

[john108]

I understand your explanation as it is similar to the service manual.  I have it in my hand now and was wondering how to test it before I install it. 

Vacuum, electrical tests??

I may not get to install and run the AC for a while.

[Bronzedodge]

Wire it in series with a small load - it should be normally closed, and then open after 10 minutes max.  The amp draw for the compressor clutch is between 2.7 to 4.6 amps, depending on weather you have an aluminum wound or copper wound clutch coil.