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erikv11

When is the AC mod needed in a flash

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Is the AC mod only needed when installing an m4.4 tune into an m4.3 vehicle, and that holds across all years?

My confusion is whether the need for AC mod is for all 850's or just 850's that came from the factory with m4.3.

So, a 97 GLT (which was already m4.4) takes a 607 tune without doing Piet's AC mod, correct?

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Only m4.3 vehicles running m4.4 need the ac mod. Anything that came with a m44 ecu from factory must not use it.

Not running the ac mod in a m43 vehicle does no harm, the ac just doesn't work.
Running the ac mod in a m44 vehicle fries the compressor.

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So we flashed a stock 4.4 tune onto a 451 ECU from a 98 S70. Turned off some emissions and sensors but NO AC mod.

Installed it into a 97 GLT 850 (should be m4.4, I haven't checked the VIN personally but it had an air pump I thought ALL 97 GLT's are m4.4). FWIW the car also now has whites and a 15g.

The AC does not work with the flashed m4.4 ECU! Runs fine, but no AC.

If you pull the flashed ECU and install the original, then the AC comes back just fine. So the car acts like it is a 4.3 car?

Any ideas? Is this 97 GLT somehow wired for m4.3?

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Only m4.3 vehicles running m4.4 need the ac mod. Anything that came with a m44 ecu from factory must not use it.

Not running the ac mod in a m43 vehicle does no harm, the ac just doesn't work.
Running the ac mod in a m44 vehicle fries the compressor.

Are you sure? Afaik you need to run the AC mod on any 850 when you flash the ecu to the newer 601(?) tune. Not the same as x70 m44 in some respect. I had to do this on my 97 glt which came with m44. FWIW I ran the mod and didn't fry the compressor.

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So we flashed a stock 4.4 tune onto a 451 ECU from a 98 S70. Turned off some emissions and sensors but NO AC mod.

Installed it into a 97 GLT 850 (should be m4.4, I haven't checked the VIN personally but it had an air pump I thought ALL 97 GLT's are m4.4). FWIW the car also now has whites and a 15g.

The AC does not work with the flashed m4.4 ECU! Runs fine, but no AC.

If you pull the flashed ECU and install the original, then the AC comes back just fine. So the car acts like it is a 4.3 car?

Any ideas? Is this 97 GLT somehow wired for m4.3?

One way to find out .....:)

Most likely the aircon in the car, being an 850, is wired like all other 850's and is the software in its original M44 adapted to this.

Therefore most likely you still have to do the AC mod.

The MOD is written for the 607 and 608 bins only b.t.w.

 

 

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Are you sure? Afaik you need to run the AC mod on any 850 when you flash the ecu to the newer 601(?) tune. Not the same as x70 m44 in some respect. I had to do this on my 97 glt which came with m44. FWIW I ran the mod and didn't fry the compressor.

Yeah the 97 850 glt s a bit of a hybrid I think. Just like the early 94 t5 was.
It may be that these still have the m43 a/c setup, and therefore require the ac mod to function.

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Are you sure? Afaik you need to run the AC mod on any 850 when you flash the ecu to the newer 601(?) tune. Not the same as x70 m44 in some respect. I had to do this on my 97 glt which came with m44. FWIW I ran the mod and didn't fry the compressor.

 

 

It's quite simple.

Cars with the older (850 style) AC units need the mod. Car's with the newer style AC units don't.

So the MY 1997 car's with a M44, but with an older style AC unit do need the AC mod.

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Right, that wasn't clear from the previous responses. Just to clarify, any 850 running m44 or 43 needs the AC mod. 

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Unless that 850 running m44 happens to have the new setup. Volvo has been a little random with that stuff sometimes.
Using it on a new style setup can  result in an engine bay fire, so it's best to be careful.
Best way to tell is to just stick the m44 with the new bin in, and see if the a/c suddenly refuses to work.
Then  you need the ac mod.

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So, let's assume I have a 850 from 1997 which came with a M4.3

It is now converted to M4.4, an RN engine and a AC compressor from a 99 vehicle. Would this need the mod or not, or in other words: is the compressor the driver for the requirement of the mod or is it something else?

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I doubt the problem is the actual compressor. More likely the CC unit. I don't understand though, you converted it to m44 and put in a new motor and never tested the AC?

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It's the way the wiring is set up that determines the need for the mod.
Simplest way to test is to see if the a/c works with the normal m44routine.
If not then the ac mod is needed.

If the m43 mod is used on a m44 car, the compressor will always run even when the a/c is turned off.
It takes a little while for it to engage after starting, but then it will keep running and overheat.
 

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It's interesting because I had always heard that if you flash an m43 to 44 without doing the AC mod, you'll fry the CC unit when you try to use the AC. Guess that was a second or third hand rumor. 

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