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sprinkles08
sprinkles08, ASE Certified Technician
Category: Cadillac
Satisfied Customers: 23109
Experience:  ASE Master and Advanced level certified. Factory trained with 17 years dealership experience
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Can you tell me the actual pin layout on the clutch relay

Customer Question

Can you tell me the actual pin layout on the clutch relay terminal block in the fuse block. According to the diagram on the relay it appears that the two pins nearest the front of the car are pins 87 and 30. I think this would be the power circuit. However, I get no voltage reading when I take either to ground. I checked another relay block for a circuit I know is working and I get no voltage on that circuit either. The k d of the fuse box says 4 pin relays can be inserted 180deg. This does not make sense to me.
Submitted: 4 months ago.
Category: Cadillac
Expert:  K. Wiggins replied 4 months ago.

On the relay 30 is power from the 10 amp clutch fuse. You should have power on this at all times

87 is power out to the clutch, you will only have voltage hwere when the pull in circuit is energized.

85 should have power with the key on, check the emmisions 2 fuse if not

86 is ground from the engine control module, this is what cuases the electormagnetic part of the relay to work and connects 30 to 87

I'll post the wiring diagram below. Let me know if I can help further.

Customer: replied 4 months ago.
I understand all that. The fuses are good. Once I pull the relay I am not sure on the fuse block what is each pin. If I look at the diagram on the relay, it shows that the two pins toward the front of the car would be 87 and 30, but since there us a note that says the relay can be installed 180deg, I think maybe it is the two pins toward the rear of the car. I need to know on the block that the relay plugs into what pin is what? As I stated, I tested a cir hit that I know is good (horn)(horn works with relay in), and I get no voltage reading when taking either front plug in slit to ground.
Expert:  K. Wiggins replied 4 months ago.

Could you post a picture of the relay cavity and the relay upside down? Usually on GM's they will only go in one way

Customer: replied 4 months ago.
I did notice this time that the pin out is wriiten on the bottom of the relay. My problem is I get no voltage reading even on a circuit I know works. I am connecting the red lead of my multimeter to 30 and the ground side to the ground cable for the battery jump. Even on a known good circuit, I get no reading.
Expert:  K. Wiggins replied 4 months ago.

The easiest way to find out which pin in the cavity is 30 is going to be to test all 4 pins with your volt meter with the key off. The only pin that will have battery voltage with the key off is 30. You can then match up the relay pin 30 to the corresponding cavity and drop it in.

You may also want to check your meter against the battery. (red lead to pos black to neg) to make sure it's working properly.

Customer: replied 4 months ago.
Here what I found. I had a problem with the multimeter which I corrected. To give you a little background...my problem is the cooling fans run all the time and the ac won't blow cold. What I have found is that I have no power to pin 30 on the engine pump relay, but I have power to the DRL/eng pump fuse. Fuse is good. Any suggestion?
Expert:  K. Wiggins replied 4 months ago.

Possibly an internal issue in the fuse box. Let me open this up to other experts to see if anyone has some mmore insight to offer.

Customer: replied 4 months ago.
A little more testing info. I ran a jumper wire from the fuses side of the DRL/Eng pump fuse to pin 30 on the eng pump relay and installed relay. Eng pump came on and stayed on. I removed the jumper. I removed the ac clutch relay and jumpered pin 30 to pin 87 with engine running. I don't believe the clutch engaged.
Expert:  sprinkles08 replied 4 months ago.

Hello and welcome to JustAnswer!

Do you still need help?

Customer: replied 4 months ago.
Expert:  sprinkles08 replied 4 months ago.

The problem you're trying to diagnose is the a/c compressor not engaging and the cooling fans are running when you don't believe they should?

Customer: replied 4 months ago.
Can you see all the previous info about this?
Expert:  sprinkles08 replied 4 months ago.

Yes, I can see the previous posts.

You need to use a scan tool to look at the a/c transducer pressure. It sounds as if you have a bad transducer that is preventing the compressor from engaging and the fans are running because it thinks a/c pressure is high.

Customer: replied 4 months ago.
Why would that prevent the eng coolant pump from engaging and why would I not have voltage to pin 30 on the engine pump relay?
Expert:  sprinkles08 replied 4 months ago.

The after run pump not running would not be related to the a/c compressor not engaging.

Pin 30 of the relay would not have power unless the relay is commanded on by the engine controller. You'd need to use a scan tool to see if the relay was even being commanded on before being concerned with this.

Customer: replied 4 months ago.
I thought pin 30 was from the fusecand should have power all the time. It does on the ac clutch relay.
Expert:  sprinkles08 replied 4 months ago.

No. Pin 30 is the output from the relay to the pump. The power feeds are 85 and 87, the ECM controls the relay on pin 86.

Customer: replied 4 months ago.
Is it different for the pump and the clutch? I have voltage on pin 30 to ground on the clutch relay but not the pump relay
Expert:  sprinkles08 replied 4 months ago.

The after run coolant pump is not in question if you're trying to diagnose an a/c problem.

Customer: replied 4 months ago.
I am trying to diagnose both as they all have to do with engine temp and ac
Expert:  sprinkles08 replied 4 months ago.

The after run pump has nothing to do with engine temperature or fan operation while the engine is running, and is not related to the a/c compressor not engaging. The after run pump only runs when coolant temperature is high enough, after engine shutdown, to prevent cooling system boiling with the engine off.

Customer: replied 4 months ago.
If you read the previous post, you know that I tried to jumper pin 30 and 86 on the clutch relay socket. This should engage the clutch but does not. Is the high pressure switch in series with this circuit so that it would still prevent engagement?
Customer: replied 4 months ago.
Sorry 30 and 87
Expert:  sprinkles08 replied 4 months ago.

It does not have a high pressure switch, it has a transducer as I previously explained.

If you believe you jumped the correct terminals and the clutch did not engage then you need to check for power at the clutch connector with the jumper in place. If there is power then the clutch coil has failed. That still wouldn't explain fans running when they should not be, but there may not really be a fan issue.

Customer: replied 4 months ago.
The fans run continuously. They come on about 5 seconds after I start the car and run the entire time. They stay on about 5 seconds after I turn the car off.
Expert:  sprinkles08 replied 4 months ago.

That's either going to be a separate problem or related to the a/c transducer.

Customer: replied 4 months ago.
Is there a way to check the transducer with a multimeter
Expert:  sprinkles08 replied 4 months ago.

You need to use a scan tool to monitor pressure as I previously mentioned.

Customer: replied 4 months ago.
Thanks
Expert:  sprinkles08 replied 4 months ago.

You're welcome!

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Good luck with your vehicle!