Quote:
Originally Posted by TrybalRage
Been a while since my swap, still running pretty good but it's time to get the AC working before the summer heat kicks in.
Got the following coming:
- Denso 4710315 compressor for an 03 Silverado
- OSC 4953 Condenser for an 03; supposedly the original one would be fine but I sorta punched a hole in it by accident and a replacement is at least twice the price of an 03, so we'll make it fit.
- ACDelco 15-681 accumulator and 15-50120 orifice tube for an 85
- Four seasons 54275 evaporator core, figure everything else is new so why not.
I'll probably use Cold Hose for the hoses and fittings, they seem highly recommended. I'll need to figure out the wiring, I plan to run everything off the existing 85 controls if I can rather than PCM driven.
|
I think this is a good plan and one I will basically emulate with my build (2001 Vortec in 1971 C10). For me, Old Air products (50-7228) makes a conversion kit for my truck (wont do you much good on your 85). But, I may try and source the stuff separately...
As for controlling the a/c, I plan on going through the ECM/PCM. Main reason is that I want the PCM to control compressor clutch engagement so that it can set the idle speed properly to account for the added load. So, what that looks like is I will connect the +12v stock/original compressor clutch engagement wire to the "a/c request" wire of the PCM (pin #17). Thus, when you turn on the a/c, voltage will be apply to pin 17 which will cause the PCM to anticipate the upcoming load and send a control output via pin #43. This control output will activate a relay that will in turn engage the compressor clutch. I rerouted the a/c request wire from PCM (it originally went to the body module) to the wire harness branch that has the a/c LP switch and HO2S sensor (right side)...I will connect this wire to the factory compressor wire. The PCM pin 43 wire is routed to the added fuse/relay box to be connected to a new relay. All wiring will still go through the a/c LP and HP switch to protect the compressor and allow cycling of the compressor.
I figure I will (have) to use the compressor fittings as linked in above post and have to custom make many of the lines. I plan on putting the 2001 Tahoe condenser in front of the radiator (much of it will be blocked by the core support). I will also mount dual fans to the front of the condenser that will be activated via relay by the control output of pin #43 (so fans cycle with compressor). BTW, I am keeping the mechanical engine fan.
FWIW, I think if you do not allow the PCM to control the compressor, you will get a dip in the idle speed whenever the compressor clutch is activated. The PCM will notice the idle dip and attempt to compensate, but because the PCM has no way to anticipate the load, it cannot be ready to compensate so it takes a few seconds. Same going the other way around. When the clutch disengages and the load is removed, the idle speed increases until the PCM (via the IAC) can compensate. If you go through the PCM, the idle should stay more consistent regardless of compressor clutch activity. Also, I think some only connect the a/c request (pin 17) in parallel with the factor compressor wire. Result is vehicle switch is controlling the compressor and the PCM has a simultaneous indication that the compressor has been engaged. This smooths the idle somewhat, but not as good as when the PCM is allowed to engage the compressor.
Or so I believe.