A/c question

Disclaimer: Links on this page pointing to Amazon, eBay and other sites may include affiliate code. If you click them and make a purchase, we may earn a small commission.

Hoosierlong90

OBS Enthusiast
Joined
Jan 3, 2019
Messages
70
Reaction score
65
Location
indiana
Hello all. I hope everyone is doing well. I have a 94 K1500 that I am doing a motor swap with. Existing motor is a 350 TBI. I am throwing in a vortec 350 using existing TBI. The billet serpentine kit I have includes a single wire A/C compressor. I understand my existing compressor has several wires , I mean a high and low. Anyone have any ideas or thoughts of a good way to run it. I do not want to run a switch to the cab, that would be annoying. I am considering hooking it up just to the low to see how it does. I love cold A/C just as next guy. This is where I'm stumped. I'm wondering if anyone else has ran into this sort of thing. Suggestions welcomed.
Thanks!
 

SAATR

/\___/\___/\___/\___/\
Supporting Member
Joined
Dec 16, 2010
Messages
2,649
Reaction score
946
Location
Loo E Z an uh
Hello all. I hope everyone is doing well. I have a 94 K1500 that I am doing a motor swap with. Existing motor is a 350 TBI. I am throwing in a vortec 350 using existing TBI. The billet serpentine kit I have includes a single wire A/C compressor. I understand my existing compressor has several wires , I mean a high and low. Anyone have any ideas or thoughts of a good way to run it. I do not want to run a switch to the cab, that would be annoying. I am considering hooking it up just to the low to see how it does. I love cold A/C just as next guy. This is where I'm stumped. I'm wondering if anyone else has ran into this sort of thing. Suggestions welcomed.
Thanks!

A picture would be helpful. Do you mean that the compressor clutch only has 1 wire?
 

1998_K1500_Sub

Nitro Junkie
Supporting Member
Joined
Jan 28, 2019
Messages
2,142
Reaction score
3,240
Location
Rural Illinois
I have a 94 K1500 that I am doing a motor swap with.

Does this truck already have AC?

The billet serpentine kit I have includes a single wire A/C compressor. I understand my existing compressor has several wires , I mean a high and low.

Assuming your truck already has AC:

The clutch on the new compressor should be connected to the existing compressor's clutch wiring. We'll discuss the "how" when you've given us more information about your compressor. (Yes, I could probably give you an answer now, but let's wait until we have all the information and then answer the question correctly, once.)

Also,...

I believe in 1994 AC systems the R4 compressor was equipped with a high-pressure cut-out switch (visible as a two-wire connector on the back of the R4 compressor). If so, you should try to provide a similar high-pressure cut-out switch function on your new compressor. This may or may not be possible.

So,...

Post pictures of the compressor (front, back, top, bottom, sides) to help ascertain where a high-pressure cut-out switch might be placed, and pictures of the wiring, and we'll go from there. If possible, provide the mfgr and part number for the compressor.

For the record, some Sanden compressors come with a fitting / boss machined into the housing specifically for placement of a high-pressure cut-out switch. Similarly, your new compressor may have a similar fitting which can simply be re-used. The pictures I've mentioned (back, top, bottom, sides) would help to visually identify this fitting, if it exists.
 

1998_K1500_Sub

Nitro Junkie
Supporting Member
Joined
Jan 28, 2019
Messages
2,142
Reaction score
3,240
Location
Rural Illinois
That looks like a single-wire connection, yes? I would expect to apply battery voltage to it to energize the clutch coil and engage the clutch. The other lead from the clutch coil is almost certainly connected to the compressor case which in turn is connected to ground via the mounting brackets.

You might want to measure the resistance between that connector and ground. I'm guessing a clutch coil might draw 2-3A, which implies the resistance would be 4-6 ohms. Or, you could simply jumper the lead to the battery and see if the clutch engages. This can be done engine-off.

Assuming I'm right (clutch has connection to ground), one could wire the compressor using simple trial and error; connect that single lead on the new compressor to one or the other of the two existing leads from the wiring harness. Whichever one works, is the one that works; likely one of the two existing leads is ground, and the other is switched battery voltage (e.g., coming from the low-side pressure switch aka cycling clutch switch). However, this isn't an absolute; it may be that one of the two leads is constant battery voltage and the other is pulled to ground by the low-pressure switch. Again... try connecting the compressor as described above. If you get the desired behavior, you're good. If not (e.g., the clutch never engages or it constantly engages / never cycles) then there's some minor work to be done. Try it out and follow-up.
 
Last edited:

Hoosierlong90

OBS Enthusiast
Joined
Jan 3, 2019
Messages
70
Reaction score
65
Location
indiana
That looks like a single-wire connection, yes? I would expect to apply battery voltage to it to energize the clutch coil and engage the clutch. The other lead from the clutch coil is almost certainly connected to the compressor case which in turn is connected to ground via the mounting brackets.

You might want to measure the resistance between that connector and ground. I'm guessing a clutch coil might draw 2-3A, which implies the resistance would be 4-6 ohms. Or, you could simply jumper the lead to the battery and see if the clutch engages. This can be done engine-off.

Assuming I'm right (clutch has connection to ground), one could wire the compressor using simple trial and error; connect that single lead on the new compressor to one or the other of the two existing leads from the wiring harness. Whichever one works, is the one that works; likely one of the two existing leads is ground, and the other is switched battery voltage (e.g., coming from the low-side pressure switch aka cycling clutch switch). However, this isn't an absolute; it may be that one of the two leads is constant battery voltage and the other is pulled to ground by the low-pressure switch. Again... try connecting the compressor as described above. If you get the desired behavior, you're good. If not (e.g., the clutch never engages or it constantly engages / never cycles) then there's some minor work to be done. Try it out and follow-up.
As I'm getting around to installing the new motor with this serpentine kit, I appreciate your help! I didn't mean to ghost this discussion without saying thank you! Everybody on here is great and always have been. Thanks again!
 
Top