GM V-8 Swap A/C question?

[Elbert]

Ok,

Its time to get the A/C going now that its full blown summer. For those with a GM-V8 and running A/C. I assume you went with the GM compressor and custom A/C hoses, while retaining the Toyota receiver / dryer , along with the other Toyota A/C components. This is my plan, so looking for comments from those what have done this:

(1) How are you controlling the A/C on switch at the dash...just using the stock push button and the A/C amplifer under the dash?

(2) To control the cycling in the A/c compressor did you just use the Toyota wire or setup some type of relay ?

(3) I'm thinking it would make good sense to setup a relay or some wiring method to use the High Temp head switch and the low pressure switch on the GM AC compressor and hose assembly to disable the compressor if I loose freon.

Plan to run R134.... with the GM compressor, custom A/C hose and the rest of the Toyota A/C components. Also will install new o rings and new toyota receiver dryer.

Comments requested.

[rchalmers3]

I don't have a GM powered rig, but I think you are right on.

#1 Yes, leave the under dash as is, unless you need to replace the thermistor for any reason, then you could bypass the amplifier.

#2 Yes, if you use the factory amp, why not use the factory power lead to the clutch??

#3 I think that would be an elegant way to control the compressor for both head temp and low pressure. In addition, I have seen some set ups that pass the clutch power THROUGH the low pressure switch with no problems. In fact, I think you may find, with some research, find this is how your GM A/C was controlled.

Best regards,

Rick

[FJKai]

I'm running everything toyota wise for my a/c stuff. I just got longer lines to allow the comp. pump to be situated on the driver's side of the engine. I recently got a skooling on the a/c button and how to make it work with the engine conversion (ask Kevinmrowland with any a/c questions, he know's his stuff). Let me just say the easiest way is to go with the 62 series a/c amp. It will cost you about $50 from Spector (that is if they have one in stock, part is no longer in production) and it's pretty much pull out the old one, clip the black wire on the vehicle harness end, plug in 62 series a/c amp, slide back into the a/c evaporator under the glove box, and then put the glove box back together. Simple and it works. Otherwise, good luck, your a/c button won't work without this simple fix, believe me, I know, I rigged up a cheap on/ off toggle switch to turn on the a/c comp. manually until Kevinmrowland told me the trick. Other than the 62 series a/c amp change out, everything in my set-up is the stock Toyota a/c parts (of course the longer lines too). Good luck. I highly recommend asking Kevinmrowland if you have a/c questions he's done it before and still doing it so he can explain the how and why things will or won't work. He may even chime in on your thread.

[sixty]

I've been running a GM compressor on my tbi350 cruiser for 8 years. All I did was use custom hoses (with a universal dryer) to attached the compressor & let the Toyota system control the compressor just like stock. Worked like a charm until this summer when the compressor went out. I plan to replace the compressor and leave the system like it is. I am currently running R12 since I live in Vegas, but am thinking about using the 134 just to see how it will perform.

[Dynosoar]

I run a GM R-12 compressor and had lines made up to fit the Toyota system. I use the stock switch and amplifier. It blows ICE cold air. The stock thermistor has a switch that cuts the compressor when low pressure is detected (I think).


Dynosoar

[rchalmers3]

FJKai is 100% right, I keep forgetting the elusive missing signal required to operate the amplifier: The ignition tach signal.

On my truck I used a relay to eliminate the amplifier, as my replacement engine was diesel and had no tach signal. Here's a diagram that will assist your understanding: http://forum.ih8mud.com/diesel-tech-...or-clutch.html

For your application, ignore the fact the compressor in the diagram is getting a 24v source. Yours will be all 12v. All other info should be the same.


I am not clear if your truck is a gasser or not. If it's a gasser, there may be a usable signal produced by the ignition that could be "piped" to your amplifier, thus making the replacement of the amp un-necessary.

If it's a diesel or a gasser without a tach lead, then it's your option to swap the amp like FJKai has done, or use a generic $10 relay to control your compressor as the thread above describes.

[Elbert]

Originally Posted by FJKai

I'm running everything toyota wise for my a/c stuff. I just got longer lines to allow the comp. pump to be situated on the driver's side of the engine. I recently got a skooling on the a/c button and how to make it work with the engine conversion (ask Kevinmrowland with any a/c questions, he know's his stuff). Let me just say the easiest way is to go with the 62 series a/c amp. It will cost you about $50 from Spector (that is if they have one in stock, part is no longer in production) and it's pretty much pull out the old one, clip the black wire on the vehicle harness end, plug in 62 series a/c amp, slide back into the a/c evaporator under the glove box, and then put the glove box back together. Simple and it works. Otherwise, good luck, your a/c button won't work without this simple fix, believe me, I know, I rigged up a cheap on/ off toggle switch to turn on the a/c comp. manually until Kevinmrowland told me the trick. Other than the 62 series a/c amp change out, everything in my set-up is the stock Toyota a/c parts (of course the longer lines too). Good luck. I highly recommend asking Kevinmrowland if you have a/c questions he's done it before and still doing it so he can explain the how and why things will or won't work. He may even chime in on your thread.

Don't know what GM engine seutp you have? I have the single belt setup that matches my 1999 engine, so you need a compressor with the clutch and pulley setup for the single belt.

Are you saying you are using a Toyota compressor? IF so I assume you have an old-school V-8 setup with V-belts? My Toyota compressor left when I sold the complete I-6 engine assembly.

For parts on my setup it looks like I need a custom hose that will mate the GM compressor with one line at the evaporator core and one line at the condensor. I will replace the dryer / receiver because I had the system open for a few days when I was removing the engine.

[Elbert]

Originally Posted by Dynosoar

I run a GM R-12 compressor and had lines made up to fit the Toyota system. I use the stock switch and amplifier. It blows ICE cold air. The stock thermistor has a switch that cuts the compressor when low pressure is detected (I think).


Dynosoar

You guys have a source on R-12? My Toyota stock system was nice and cold (R-12). Only reason to run R134 is the avability issue of R-12. I still have a set of the old AC guages for R-12.

[Elbert]

Originally Posted by rchalmers3

FJKai is 100% right, I keep forgetting the elusive missing signal required to operate the amplifier: The ignition tach signal.

On my truck I used a relay to eliminate the amplifier, as my replacement engine was diesel and had no tach signal. Here's a diagram that will assist your understanding: http://forum.ih8mud.com/diesel-tech-...or-clutch.html

For your application, ignore the fact the compressor in the diagram is getting a 24v source. Yours will be all 12v. All other info should be the same.


I am not clear if your truck is a gasser or not. If it's a gasser, there may be a usable signal produced by the ignition that could be "piped" to your amplifier, thus making the replacement of the amp un-necessary.

If it's a diesel or a gasser without a tach lead, then it's your option to swap the amp like FJKai has done, or use a generic $10 relay to control your compressor as the thread above describes.

Yes my engine is a 5.7 V-8 Gas burner... I do have a tach signal coming off the ECM. I've not yet installed a tach, but I assume the signal works. Have not bothered to screw with the stock tach.

[rchalmers3]

Originally Posted by Elbert

Yes my engine is a 5.7 V-8 Gas burner... I do have a tach signal coming off the ECM. I've not yet installed a tach, but I assume the signal works. Have not bothered to screw with the stock tach.

If you desire to do so you can investigate the compatibility of the signals for supplying your amplifier with the necessary input to operate the compressor.I don't have specifics, but if the signal is "close" (switching hi to low with proper voltages) it may not matter if the amp sees a 8 lunger vs a six.

If you don't want to study and test the compatibility, either read and follow KevinTML's thread or use a relay to operate the compressor.

Rick

[Dynosoar]

I have heard that you can get R-12 in Mexico it's like $5.00 per can off the shelf in any of the 1,000,000 auto parts stores in Tijuana. However it is a BIG NO-NO to import this to the US. So I would NEVER do such a thing.


Dynosoar

[FJKai]

Bingo! The missing single from the tach. That's what was explained to me. I'm not running the stock tach since the engine swap.

Just running an old school sbc with the a/c all toyota.

[GM60]

My hj 60 was fitted with an aftermarket AC.
When I fitted the 6.2 GM I just used the same compressor in a custom mounting bracket.
The same AC button works fine on this setup.

[Elbert]

Yeah on the R-12 thing.... It would be COOL . Just assuming one were to use that stuff, you might expect the system to function fine as far as performance goes. I know the modern vehicles have larger condensors in order to make the R134 systems more efficient relative to the R12. I don't plan on trying to adapt another condensor.