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Vintage Air Wiring

Mjkbugs on Mon May 30, 2011 10:54 AM User is offline

Year: 1975
Make: Toyota
Model: FJ40

New here, used your search function to see if this had already been answered but couldn't find an answer, so any help you can provide will be appreciated.
I just installed a 2002 Chevy 4.3l V6 out of an S10 pickup into a vintage Toyota Land Cruiser, also installed the Vintage Air Fj40 kit and I am using stock Chevy compressor. The directions that came with the Vintage Air kit show me how to wire the compressor clutch (to a pressure switch that came with the kit), but according to the donor vehicle's wiring diagram, there is a Compressor high pressure safety switch located on the back of the compressor. Not knowing what to do with the wiring for the compressor safety switch I called Vintage Air and they said they couldn't help at all because they didn't know anything about GM compressors (strange, to say the least).
The wiring diagram for the motor shows one wire from the compressor's high pressure safety switch went to the heater / AC controller and the other wire went to the ECM for the A/C request signal. I had previously modified the ECM and wiring harness to be stand alone, so the ECM no longer has any A/C control functionality.
Can anyone here help me figure out what I need to do with the wiring for the stock compressor's high pressure safety switch. Thanks.

NickD on Mon May 30, 2011 12:24 PM User is offline

Assume you are switching over from a TXV to a CCOT system with the high pressure cutout switch and the cycling switch with the latter sitting on the accumulator rather than using the receiver that was original.

Need 12V coming from your climate control when in any of the AC modes, typically in series with the blower switch that has to be in one of the on positions, also may have an AC switch on your climate control, that can be left in series with this lead. That will go to your cycling switch, then to the high pressure cutoff switch, then to the solenoid of a relay back to ground. Relay contacts can go to a fused always hot, then to the compressor coil back to ground.

Cycling switch will open in around 35*F or lower ambients or in case of low refrigerant, high pressure switch will open in about the 40-430 psi range to keep your system from blowing up if you condenser plugs up or your fan quits.

Mjkbugs on Mon May 30, 2011 4:53 PM User is offline

Thanks NickD for the quick reply, to dumb it down a bit for me, because I don't get this stuff, and probably why it's left to experts such as yourself. The info in your first paragraph went completely over my head, I'm a builder/ fabricator so i apologize for being dense
The vintage air system (which apparently doesn't use this compressor's internal high pressure switch at all) protects against high pressure by dumping the clutch at over pressure via a binary type switch in one of the lines, can I just then wire this internal switch in series with the vintage air high pressure switch, or just connect the two leads together, i.e. Closed?
Sorry, if I 've got this wrong, is there a diagram that you could point me to? Thanks again.

ice-n-tropics on Mon May 30, 2011 4:56 PM User is offline

The Vintage Air Kit has a binary pressure switch (two terminals) which interrupts the clutch circuit at excessive high pressure (406 psi). If you got the trinary switch to control a relay for a electric condenser fan, it has the same high pressure protection.
You can bypass the redundant GM switch in the compressor head.
Hope this helps,

Isentropic Efficiency=Ratio of Theoretical Compression Energy/Actual Energy. How To Air Condition Your Hot Rod

Mjkbugs on Mon May 30, 2011 7:20 PM User is offline

Great, thanks. By bypass do you mean ignore it altogether, or connect the two leads on the compressor switch together? Thanks again.

mk378 on Mon May 30, 2011 9:11 PM User is offline

Just leave it unwired. The other switch in the the kit will protect the system. You could put a blank plug into the compressor port instead of the switch for a cleaner look under the hood. These plugs come with some new compressors I don't know if they're able to be bought separately.

Edited: Mon May 30, 2011 at 9:12 PM by mk378

NickD on Mon May 30, 2011 10:34 PM User is offline

We should agree on what kind of system Mjkbugs wants to use first. I assumed with a GM compressor of switching it over to their standard CCOT system as the TXV original compressor does have kind of a oil sump because of the low refrigerant flows with the TXV system. GM compressor are designed to operate a full blast, then go completely off.

I actually prefer the TXV system as these compressors cycle far less, especially in cooler temperatures. Perhaps, should have said, stick with the Toyota compressor and leave the rest of the system stock. If going to a CCOT, wouldn't really recommend using the dual function switch, this switch works in conjunction with an evaporator core temperature switch where the evaporate temperature actually controls the cycling, mainly to prevent evaporator core freezing. These switches are low current devices that feed into an AC amplifier.

But before going further into this, what kind of system is Mjkbugs going to stick with. Easiest way out, would be to use a Toyota compressor and kept it stock.

Mjkbugs on Tue May 31, 2011 4:02 PM User is offline

I bought the Vintage Air kit (without compressor) designed specifically for the Toyota FJ40 and the early Ford Bronco. My FJ40 did not have stock air conditioning. Prior to purchasing the kit I did an engine and drivetrain swap, swapped from the stock Toyota inline six and 4 speed manual to a 2002 Chevy 4.3L Vortec V6 and a 4L60E electonically controlled automatic transmission.
So it's not a matter of what I want to use, it's a matter of using what I bought/have if it will work. Vintage Air said, prior to purchase, no problem with using the late model compressor (that was already on the V6 when I purchased it) with their kit. But when it came time to wire it the question of the high pressure switch on the stock Chevy compressor came up. And as I said ealier, Vintage Air was of no help in answering that question.
So, assuming as some of you have said, this compressor will work with the Vitage Air kit, I will leave the high pressure switch on the back of the compressor disconnected and utilize the pressure switch that controls the clutch on the compressor. Thanks again. mb

NickD on Tue May 31, 2011 6:48 PM User is offline

You are required by the EPA to have a HPCP switch, but most important for your own safety. You met that requirement if that kit already has one, not typical for Toyota to install these on the compressor, but is installed in the high pressure line, where GM installs them on the compressor. That switch on the back of the compressor will always be a short circuit, unless that compressor sees around 430 PSI, then it becomes an open circuit that is suppose to kill the compressor clutch, so you could mount that in series with the kit HPCO off switch for extra safety, or just leave it. But if you kit does not have a HPCO switch advisable to use it. Vintage Air should know that.

The way you test a HPCO switch is to put an ohmmeter across the two contacts, should show a short circuit or zero ohms. Then you require a high pressure source as a liquid nitrogen with a regulator and a precision gauge and slowly increase the pressure using a jig to attached to the switch until those contacts open, generally around 400-430 psi. Ohmmeter will show infinity at this point, then decrease the pressure, the contacts should close again around 220 PSI.

So what it does, is if your pressure should ever reach that high value, it simply shuts down the compressor. Without it, the pressure will keep on increasing until something blows.

Typing this so you have an understanding of what this switch does. It is very important to have this compressor switch or another one somewhere in the high pressure line to do this.

Mjkbugs on Tue May 31, 2011 9:00 PM User is offline

Thanks for all the help guys, thanks too for the explanations, I'll get it charged this week and let you know the results.

NickD on Wed June 01, 2011 4:57 AM User is offline

Still a question as to whether that GM compressor will have sufficient lubrication, but time will answer that question.

Other minor issues are EPA emission requirements, and liability insurance problems when making an engine swap, Engine swaps were a lot of fun when we lived in a free country. But that is also part of our history.

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