roundhouse

OK,

so I have a 95 4 runner
had a small underhood fire, along with a blown headgasket.

Swapped the 3.0 auto for a 1KZT turbodiesel 5 speed with a mechanical pump, so no computer at all. 1 wire to the pump, 1 wire to glow plugs.

Im not getting any voltage from the B/W wire from the A/C amplifier at the connectors on the passenger kick panel.

obviously Im missing all the sensors that are/were under the hood.

How much can I bypass without damaging the system or burning up some wires.?

none of the older cars from the 70s had any of the computer stuff, just a low and high pressure switch, the adjustable temp thermistor setup,

I know I need to bypass the A/C cutout relay, and the engine temp sensor,
what else?

I have a wiring diagram, but not sure how it all works,

Ive grounded the pink wire from the engine temp sensor.
but dont know what else I have to do to get the amplifier to turn on the compressor.
Attached Images

RJR

The AC amplifier is looking for a pulsed signal from the ignitor on pin 6 (black wire). That signal tells the AC amp that the engine is running above minimum speed, so it's OK to turn on the compressor. Since you have a diesel, there's no ignitor, so the AC amp will never turn the compressor on.

Here's a suggestion to get it working. Unplug the connector from the (now useless) AC amplifier. Get a 10 amp 12V relay, and wire the contacts between pins 3 (red/green) and 7 (black/white) of the AC amplifier connector. Wire the coil of the relay between pin 4 (black/yellow) of the AC amp connector and ground. The relay will turn on whenever the AC switch on the dash is engaged, and the compressor will cycle on and off based on the pressure switch. You lose the function of the AC thermistor, but the thermistor is somewhat redundant with the low-pressure switch. Whenever the refrigerant gets too cold (below about 35 degF), the pressure will drop and the compressor will shut off. The compressor will cycle on and off more frequently than if the thermistor was active, but GM vehicles were made for years with just the pressure switch, and the compressor clutches seemed to hold up OK.

The alternative is to reverse engineer the AC amplifier and figure out how to drive pin 6 to fool it into thinking it's getting a valid "engine running" signal. That'll be more of an electronics project.

roundhouse

hmm,


will give it a try.

the mech pump has a hall effect sensor to deliver a signal to operate the tach, but I cant figure out how to wire it up.

or if it even works, I get no measurable signal from it.

roundhouse

I installed a ABS sensor on the crank pulley to get the tach working.

Wonder if that signal from that will work on the amplifier?

I may just wire it straight to the a/c switch for now.