AC Compressor Switches (Page 5/7)
RyuKyu567 APR 10, 04:00 AM
Ive been following this thread for some time now and am just about to install the HR6 compressor with the new switches as described above. Currently I have the MT0671 and the MT0678 switches in the compressor which were described.

Now since they have changed the switches from the single wire to the 2 wire I am a bit confused on which wire to use to properly connect it. So just to make sure that everything is done correctly I have a few questions:

1: For either of the 2 switches does it matter which wire is the ground or is it specific? *FOUND ANSWER* must have missed it


quote
Originally posted by randye:

To wire them into the OEM harness is fairly simple. You will just cut the original single switch wires on the car, (do one at a time so that you dont confuse the high pressure cutoff switch with the fan switch), and simply splice in one of the two wires from the new switch plug.
The 2nd wire from each of the new plugs is a ground wire and you should run each of these wires to a good ground on the chassis or engine block.

NOTE: It doesnt matter which of the 2 wires you choose to splice into the harness or run to ground. Both switches simply complete or interrupt a circuit to ground. The reason for the 2 wires on the new switch connectors is that the old single wire switches grounded through the body of the A/C compressor and the new switches do not. Therefore the separate ground wire is required.



2: If the ground wire needs to be connected to something on the High Pressure switch where would be a good location to connect it?

HR6 Compressor related question:

Since the HR6 comes with oil I will imagine that it comes stock with the PAG150 oil. I have flushed the lines of the system but am concerned to the impact of the oil with the old mineral oil that was probably in the system during the old R12 days that may still be present in the evaporator core and possibly the condenser. Will this have any affect on anything in the system?

I may have other questions so I thank you in advance

[This message has been edited by RyuKyu567 (edited 04-10-2017).]

RWDPLZ APR 11, 06:12 PM

quote
Originally posted by RyuKyu567:

HR6 Compressor related question:

Since the HR6 comes with oil I will imagine that it comes stock with the PAG150 oil. I have flushed the lines of the system but am concerned to the impact of the oil with the old mineral oil that was probably in the system during the old R12 days that may still be present in the evaporator core and possibly the condenser. Will this have any affect on anything in the system?

I may have other questions so I thank you in advance




Never assume, always check the documentation, or email the manufacturer. Really doubt it comes with PAG150.
crazyd OCT 14, 05:53 PM
It's been my turn to go through this again this summer. When I bought a new 4 Seasons compressor it came prefilled with 3oz of oil and a sticker on the ports noting it. With the same concerns about existing mineral oil in the system, I called them and asked what kind of oil it was. PAG150 was the answer. Drained it and refilled with Ester.

Other notes:

- For the fan switch, R-134A retrofitted cars (which should be everyone in 2018) apparently need to use the gray/black switch, Murray #35969 instead of the purple one. I was unable to find one with a complete kit and had to buy the harness separately. I'm not completely sure what the correct part number for the harness is yet, will update this post when I know for sure.

- If you're going to change the compressor on a V6 car you will have to lower the cradle to do it - there's just not enough room to get a wrench with enough leverage in there for the upper bracket bolt. The basic pivot technique is adequate with just detaching the dogbone, not the full pivot with the struts detached. Remove the firewall heat shield and the lower exhaust heat shield too.
wgpierce OCT 14, 06:32 PM

quote
Originally posted by crazyd:

- If you're going to change the compressor on a V6 car you will have to lower the cradle to do it - there's just not enough room to get a wrench with enough leverage in there for the upper bracket bolt. The basic pivot technique is adequate with just detaching the dogbone, not the full pivot with the struts detached. Remove the firewall heat shield and the lower exhaust heat shield too.



It can be changed without touching the cradle. The trick to the top bolt is to come from behind through the rear bolt hole. Put a quarter extension through the hole, attach a socket, and twist away.
randye OCT 14, 06:52 PM

quote
Originally posted by wgpierce:


It can be changed without touching the cradle. The trick to the top bolt is to come from behind through the rear bolt hole. Put a quarter extension through the hole, attach a socket, and twist away.



YUP
That is 100% correct and exactly the way I did it my first time several years ago.

[This message has been edited by randye (edited 10-14-2018).]

crazyd OCT 15, 12:43 AM
Cool trick... would take a pretty long quarter extension to work but yeah, I can see it. It isn't a big deal to pivot the cradle down though. Any time I'm working on the firewall side I just drop it down and make some room. And the more often you work those cradle bolts the less likely they are to seize up.
Bryanketels OCT 10, 10:48 AM
Can you use the high and low pressure switches from the old compressor in the new compressor or do I need to use the new switches that came with the new compressor and just replace the stock connectors?
RWDPLZ OCT 10, 11:22 AM
You can reuse the old ones if they're in good shape, but at this point they're so old you might want to use new ones, especially if you have them already.
skywurz OCT 14, 02:14 PM
The old ones may be R12 and will not be the right pressure for 134A
RWDPLZ OCT 14, 10:33 PM
The compressor-mounted switches are the same pressure for R-12 or R-134A. The only one that is refrigerant specific is the cycling switch on the accumulator for DA6 and HR6 compressor vehicles (set to 25 psi for R-12 or 21 psi for R-134A)