ofelas

Hi all,

91.5 W250, need some AC & OD wiring pointers

1/ Where do I wire an additional momentary switch (second-gen shift lever) to act in series with the factory dash mounted OD switch? This is the red-headed stepchild 91.5 with the OD control module behind the glovebox, and the truck doesn't have the normally used OR/WH wire on the factory OD switch.

2/ Looking at the schematics - there seems to be no AC relay and ECM pin used for the compressor clutch cycling, unless I'm missing something.

Relevant FSM wiring diagrams attached; thx in advance.

j_martin

The OD lockout switch is a spst NO switch. The toggle is electronic inside the controller. You can wire an additional switch in parallel with it. The OD light on the factory switch indicates the state of the toggle in the controller, and will work with either switch in the above described parallel circuit.

You are right. The only AC control is the heater/AC switchgear and operational controls in the system. There is no ECM control as in later models.

ofelas

Understood.

The second gen lever has 2 wires - assuming I ground one, which color wire do I splice the other wire into on the factory OD switch and/or OD module ?

On the AC - without an external relay from the factory, does all the juice flow through a fusible link?

j_martin

It appears you need a dry circuit spst NO switch connected across the present OD switch. It closes a circuit in the control module. If there are 2 wires independently connected to the OD lockout switch in the 2nd gen, and it is a spst momentary switch, it will work. Neither wire should be connected to either power or ground. If the 2nd switch is wired to other circuits such that it is connect to ground or power, the function could still be supplied using a small relay.

The AC electronic clutch cycling switch appears to be acting as a relay among other functions. Supply is DB coming from page 22. DB is typically ignition switch through a fusible link.

ofelas

Yes, the second gen OD switch at the end of the shift lever is a SPST momentary, with 2 independent wires.
Which color wires on my 91.5 OD switch or OD module should I splice these 2 independent wires to?
On a 93, ground + OR/WH works, but not on my 91.5 with OD module.

j_martin

Yellow

ofelas

Both wires to Yellow?

What color tracer ? (theres 4 yellow wires)

j_martin

Be sure the action of the switch is momentary, normally open.

ofelas

I know it's momentary, but not sure if it's NO.
It acts exactly like the dash mounted factory switch in the 92-93 when one wire is grounded and one wire is spliced into the OR/WH on the 92-93 factory OD switch.

j_martin

Use an ohmmeter and check it out.

ofelas

Any chance on providing a step by step ?

ofelas

On the SD-709 I picked up from a 93 D-250 - any idea what the refrigerant capacity is if I use my 30lb jug of R12?
And if I go Duracool or R134, how much should I put as a percentage of R12 ?
Need new fittings for Duracool ?

j_martin

1. There's a label on the truck, and the info is in the FSM.
2. DuracoolŽ.com 2004 - DuracoolŽ is The Recognized Leader In Hydrocarbon Refrigerant Technology
3. No

ofelas

1/ no label, and I got the entire AC system from a 93. My 91 FSM lists for the 91 and the charge amount is not listed in the 91.5 supplement for the SD-709

You obviously know a lot, but it's like pulling teeth sometimes to get the rest of the info ;-)

j_martin

As I said in the PM, keep it private please.