I have an '88 formula with the 2.8. I am just starting my TDC conversion but I am not ready for the swap. My DA-6 compressor needs to be replaced and I thought I might try to convert to the V5 compressor as is used on the TDC and four cylinder fieros. It looks to me like the only difference between the compressor on The TDC and the compressor on the 4 cyl fiero is the connector right behind the clutch. Assuming that I can mount the V5 compressor on the 2.8, is there anything else that I have to change besides the AC hoses that go to the back of the compressor?
All you guys that did TDC conversions: Which compressor did you use and what m ods did you have to make?

I used the 3.4 TDC AC compressor with the 87/88 Fiero AC lines. The pressure switch has to be added to the front compartment, and wires ran to the ECM for it. I never did finish hooking it all up though.
In case my TDC's AC compressor is bad, I would be interested in using the 88 2.5L Fiero compressor as well.

quote Originally posted by sd_iconoclast: I have an '88 formula with the 2.8. I am just starting my TDC conversion but I am not ready for the swap. My DA-6 compressor needs to be replaced and I thought I might try to convert to the V5 compressor as is used on the TDC and four cylinder fieros. It looks to me like the only difference between the compressor on The TDC and the compressor on the 4 cyl fiero is the connector right behind the clutch. Assuming that I can mount the V5 compressor on the 2.8, is there anything else that I have to change besides the AC hoses that go to the back of the compressor? All you guys that did TDC conversions: Which compressor did you use and what m ods did you have to make?

The easiest way to go is to just use the TDC compressor with the 87-88 Fiero 4 cyl AC lines/manifold. The V6 Formula AC lines will interfere with the TDC oil filter/oil cooler setup as seen in this photo of the 2

Then you will run a high side pressure sensor off the high side port up front in the Fieros spare tire compartment.

quote Originally posted by Erik: Then you will run a high side pressure sensor off the high side port up front in the Fieros spare tire compartment.

Thanks Erik, this is exactly what I need. I understand the part about using the four cylinder AC hoses. But I do not understand the part about the high side pressure sensor. Why do I need a high side pressure sensor? Once installed, what does the high side pressure sensor connect to electrically? Is the original electrical setup in my Fiero dormula capable of running this setup?

quote Originally posted by sd_iconoclast: Thanks Erik, this is exactly what I need. I understand the part about using the four cylinder AC hoses. But I do not understand the part about the high side pressure sensor. Why do I need a high side pressure sensor? Once installed, what does the high side pressure sensor connect to electrically? Is the original electrical setup in my Fiero dormula capable of running this setup?

You need the sensor because the DOHC ECM requires it in order to now if there is enough pressure to activate the AC clutch relay and to shut the compressor clutch off is there is too much pressure. The AC pressure transducer sensor connects to the 9396 ECM @ ECM pin C5, C7 and C21( I am assuming that you will be running the 9396 ECM that came with the 91-93 DOHC

quote Originally posted by Erik: You need the sensor because the DOHC ECM requires it in order to now if there is enough pressure to activate the AC clutch relay and to shut the compressor clutch off is there is too much pressure. The AC pressure transducer sensor connects to the 9396 ECM @ ECM pin C5, C7 and C21( I am assuming that you will be running the 9396 ECM that came with the 91-93 DOHC

I do intend to use the '91 DOHC ECM, but I was hoping to get the V-5 working with my current ECM in advance of actually doing the TDC conversion. I am not ready to do the engine swap yet, but I need a new compressor now. Is there some sort of stand alone box that will work to control the compressor clutch for now? Do you know if the ECM simply turns the clutch on at one pressure and off at another? I could build a box to do that.

In a V5 system....

You have two pressure switches wired in series with the AC controls.

The AC control must be on.
The High Pressure switch must be closed indicating you are under 300 PSIG. (This switch will open with the system running AND over charged or something like orifice tube blocked.)
The Low Pressure switch must be closed indicating you are over 20-30 PSIG. (This switch will open if there isn't enough refrigerant in the system.)

(The pressures are just from memory. they may be a bit higher/lower.)

On clutch slapper systems (DA6/HR6) you also have a clutch switch that cycles to control system pressure.

When all these conditions are met, the ECM will see an AC Requested signal. The ECM/PCM will then fire the AC Enabled line to activate the AC clutch. Why does the ECM get involeved anyway? The ECM is often programmed with a cutoff to kill the AC clutch when you mash the gas.

Some V5 have both switches on the compressor. Others have one on the compressor and the other on the plumbing.

Exactly how the limit switches and AC controls connect to the ECM/PCM may vary from one model to another but that is the short version of how the system works.

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The Ogre's Fiero Cave (It's also at the top of every forum page...)

So how would one go about making a V5 compressor work on a 2.8 V6? I might be doing just that in the near future.

For Fiero... both systems are electrically similar except that V5 would eliminate the clutch cyclce switch usually found on the accumulator. You may have to do some wiring to accomodate the V5 high and low limit switches. I think they use different plugs among other things.

Mechanically you need the right hoses brackets and pulley.

Otherwise the systems are the same far as I can tell... All Fiero seem to use the same condensor evaporator orifice and accumulator.

Ironically, it'll be a 2.8 installed into a V5 equipped car, rather than vice versa.

Thanks for the info. This thread hijack is now officially concluded.

[This message has been edited by Blacktree (edited 06-18-2005).]