oledummy

I have an 1998 Cherokee Sport in which the AC will run continuously while the motor is running whatever the selector switch is set to. When I cut the motor off and put the key in my pocket I have to pull the relay to get the clutch to de-energize.This is a brand new relay.
I'm wondering how the relay can be triggered with everything off, or rather how many ways.

oledummy

I tried removing the wiring harness to the lps and have the exact same issue so whatever is trying to energize the clutch relay is not contingent on the lps being satisfied.
My question is just this: What is upstream from the clutch relay coil?

bluejeep2001

I need some time to get the wiring prints into this site...but the V in to the relay go through the ign switch in the start and run pos only. That voltage comes into relay on B5. The ground to energize the relay B3 comes from the PCM, c1 on the C3 connector based on the selections made on the heater/ac control panel. B3 on the relay or base goes to the pcm. The batt volt to the clutch goes into the relay on B1 and out on B2 if relay energized. The clutch is permanently grounded so if you get volts in it engages. Silly question, how do you know the AC clutch is locked with the key in your pocket. You would need a short to volts on the ign switch and a short to ground at same time. Disconnecting the hi or low pressure switch should interrupt the normal on signal from pcm. You are sure the clutch does not turn with relay out and truck running. I had one lock up once and could not turn off no matter what

oledummy

It seems whatever fires the relay is constantly in the state of doing so. It is scary to me that the pci may possibly be responsible for this problem. It doesn't matter whether the ignition is on at all. I can put the relay back in, hear the clutch engage, start the jeep and the a/c will run and cool and sooner or later start freezing up as nothing cycles it off. The lps is not even be involved in this as I can unplug it with no effect.
I'm hoping the pci is not involved needless to say.
I am going to take out the climate control panel(if I can get it out without breaking it) and see if there is anything that changes.
I.m keeping the information you've sent and try to use it to find out a little more.. Thank you.

bluejeep2001

The problem must be twofold because there should be no voltage at the " in" side of the relay because of the ignition switch should be killing it except in start and run....and the computer pcm gives the ground based on signals from control panel and lps and hps. In a 98 the aux cooling fan should run whenever the clutch relay is engaged..does it?

oledummy

2fold sounds like my kind of problems with this jeep.
I want to make certain that we are on the same page.
I feel sure that the power from the ignition is being routed when and as it should be.Ignition sw to one side of the contacts through the other of the contact when the coil is energized and through to the compressor.
I envision these type sof in a linear manner.
What seems to be the problem is that the control voltage to the coil of the relay that pulls the power contact closed is constantly energized. If the pcm triggers that coil to pull the relay in I suppose I have a bigger problem if it is in the pcm.
The the other side of that coil is supplied from somewhere. If one side is from the pcm, the other side must supplied from somewhere.
I have a climate control panel the same as the one on this jeep. I notice there seems to be more electrical terminals than needed for a fan speed switch.I thought maybe that is what is supplying that coil.
The schematics I have looks didn't show or maybe I just didn't see the information I need for this.
With the weather changing, I may have time to get this done by spring.

bluejeep2001

I will attempt to load the wiring diagrams. The control panel has nothing to do with supplying power to the relay, that comes directly through the ignition switch in start and run. The control panel along with other things sends signal to the pcm and that computer decides to put a ground on the b3 wire of the relay causing it to energize. . You need both the voltage and the ground to energize the relay. When energized the opposite contacts close and allow battery voltage through the relay to the clutch . The clutch is bolted to ground so when it gets power it engages

oledummy

I looked at a surprising place for more info and was surprised by the answet I got.
From Chatgpg:

In a 1998 Jeep Cherokee Sport, the air conditioning system relies on two primary sources for its operation:

Power Supply to the A/C Relay:
Battery Positive (B+): One side of the air conditioning relay coil is connected to the battery positive terminal through a fuse in the fuse box. This provides the necessary power for the relay to be energized.

Grounding for the Relay:
Control Signal from the ECM or HVAC Control Module: The other side of the relay coil is connected to the engine control module (ECM) or HVAC control module, which grounds the coil when the air conditioning is turned on. This completes the circuit and energizes the relay.

Here’s a step-by-step breakdown:

Power from Battery:
The fuse box provides a constant 12V positive supply to one terminal of the relay coil. This power is routed through the fuse dedicated to the air conditioning system.

Control Signal for Grounding:
The other terminal of the relay coil is connected to a control circuit within the ECM or HVAC control module. When the air conditioning system is activated, the control module grounds this terminal, allowing current to flow through the relay coil.

I pulled the climate control panel and disconnected the wiring harness and put the ac relay back in and it did not engage.
So now it seems that the coil for the relay is powered from one side by 12V + from the battery through a fuse. The other side of the coil that controls the relay comes from the PCM as you described. The positive feed to the PCM comes from the climate control panel, and that returns the Neg to the coil of the a/c relay that fires the relay.
I have another climate control panel.I compared continuity between terminal on both and there is difference.
As one is designed for a stepper motor for the heat control and the other for cable operation, I intend to exchange the elctrical socket and see if that helps.
I doubt it as the PCM is still sendin that negative voltage to the coil of the ac relay.
I woul love to view those schematics you mentioned if you can.

bluejeep2001

Give me a couple of days.. tough to do when not at work and im a computer dinosaur

oledummy

I thank you.
I have ordered the climate control and will change that, but I am thinking PCM problem.

bluejeep2001

here are the prints I think you needed