A/C clutch wiring had been cut-off from ECM and AC switch

NIñO REGALA

MEMBER
1999 HYUNDAI ELANTRA
2.0L
4 CYL
2WD
MANUAL
160,000 MILES

Hello guys, Good day.

It started when a mechanic tried to fix my car wiring and suddenly power to my A/C switch was gone.

I couldn't get the mechanic to redo what he did.

So what he does is totally bypass the connection of my ac clutch from the ECM.

Whenever my A/C clutch kicks in, my rpm momentarily drop to almost 200 then goes back to normal rpm 800-1,000 rpm and sometimes stalling the engine.

My question is, how can I reconnect it back to my ECM? I don't know where the pins of A/C clutch relay and A/C switch on the ECM.

And, is there an easy way to bump my rpm whenever A/C clutch kicks in without going through the ECM?

Any help would be appreciated. Thanks in advance.

PS. My idle up is working. Also, I still notice an rpm increase whenever I turn on the blower knob and when condenser fan engages.

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7 Replies

KASEKENNY

MECHANIC
18,907 POSTS

I am not sure I understand how he bypassed the clutch from the ECM but it still works. Do you mean he hard wired it so the button does not turn it on or off anymore? Basically the AC system is on all the time now so the clutch just keeps cycling?

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Saturday, February 1st, 2020 AT 6:26 PM

NIñO REGALA

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4 POSTS

Yeah he hard wired the clutch. He used and installed a manual thermo switch and that switch controls the cycling.

The current wiring from what I have observed is.

Battery -> AC relay -> mechanical thermostat switch -> AC clutch.

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Saturday, February 1st, 2020 AT 7:07 PM

KASEKENNY

MECHANIC
18,907 POSTS

Okay. The way in which the compressor is engaged should not cause this whether that is a new switch or the factory switch. The engine bogging down like this is probably due to the compressor or the clutch.

Just to get on the same page, are you looking to put it back the way it was (undue what he bypassed) or are just wanting to solve the bogging down?

I suspect the way to fix this is replace the compressor. The compressor is "tied" to the crank by the serpentine belt so when this engages it bogs down the engine by adding the load to the crank pulley.

What this happening before he bypassed the switch or was the compressor not working?

https://www.2carpros.com/articles/re-charge-an-air-conditioner-system

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Sunday, February 2nd, 2020 AT 3:18 PM

NIñO REGALA

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4 POSTS

Thanks for the help so far KASEKENNY1.

But I'm not sure if its on the compressor. It was working fine before the bypass. No drop on rpm or anything.

Right now, my main target is to reconnect back my ac clutch to the ECM. So that the computer will bump the IACV to increase whenever the A/C clutch kicks in. I need to find the wires of my A/C clutch, A/C switch, and A/C pressure switch.

If the above isn't possible, then I have to solve the bogging down of the engine. Because, i'm afraid this would cause more issue to the engine if left unsolved.

Things I notice is that I still see a timely increase of rpm (150-200 rpm's) in like every 2 minutes as if the computer is thinking that A/C is still connected. But the increase of rpm is way to early since A/C clutch kicks in after 10-20 seconds.

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Sunday, February 2nd, 2020 AT 8:43 PM

KASEKENNY

MECHANIC
18,907 POSTS

Not sure why I didn't think of this before. The ECM knows when it is going to kick on the compressor so it can pump the idle if needed. Now you are just getting an added load to the engine and it doesn't compensate.

Is there a reason he did what he did? Why was it bypassed? I included the wiring diagram. We need to wire it back the way it was or take it back to him and have him undue what he did.

What was the issue before he did this?

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Monday, February 3rd, 2020 AT 5:11 PM

NIñO REGALA

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4 POSTS

Thanks. Will find the previous wires of my A/C.

The reason was totally unrelated to my current problem. I asked him to fix my headlight wiring since my high beam isn't working. He decided to cut some saggy wires, I asked if that will affect anything and he said no. I thought he knows what he was doing so I agreed.

Later on we found out that the A/C isn't working anymore. No lights on the dashboard A/C button and A/C clutch isn't engaging.

Any idea how I can test each wires to see if they are really for A/C system? I checked the wires earlier today and it's a lot of wire under the steering column.

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Tuesday, February 4th, 2020 AT 2:52 AM

KASEKENNY

MECHANIC
18,907 POSTS

You can test each wire but the way to do it is very cumbersome and not easy. Basically you have to check for what is called continuity from end to end. This will tell you if the wire is where it is supposed to be.

It can be done but if it were me, I would take it back to him and tell him to put it back the way it was so that you have the original issue unless the head light issue is repaired. I have no idea why he would decide to cut some wires out and then hard wire the A/C clutch. Does this person own a shop or was it just someone doing it as a side job? If they have a shop, I would take it back.

Otherwise, I will get you the complete wiring diagram and you will have to check continuity as I stated earlier. I am just trying to save you a major headache because trying to figure out what someone did without a wiring diagram is the hardest thing to do in automotive work. Wiring is complicated as it is when you have a diagram that tells you exactly what wire is where. Without knowing everything they did, you will need to trace it and that is difficult.

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Tuesday, February 4th, 2020 AT 4:03 PM