Relay Socket in Fusebox 12v Query

[Trucklord]

Hi Folks.I bought a car yesterday and the Rear Demister isn't working.
I have checked continuity at the rear window end from terminal to terminal - all ok.
The switch in the car does not light up when you press it - it's a kia Sorento 2010 and the switch is part of a cluster of controls.

My query is this:
I have checked the fuse and relay are OK - BUT when using a multimeter on volts, connecting the black wire on the multimeter to the negative battery terminal - I am getting a 12v reading on the relay socket at 30, 85 AND 86 !
I thought I would get 12v at 30 and 85 but not 86 as well ?
I also took the cover off the relay and attached the multimeter to the rear demister connectors and pushed the relay switch arm to make contact and got 12v at the demister connections.
It just seems off that I would get 12v power when touching pin holes 85 and 86.

Any help appreciated please.
Thanks

 

[ycgoat]

It may just be disabled. I do not have a diagram so the terminal numbers are of no help

 

[Ole Slewfoot]

Jumping the switched side connectors should tell pretty fast if it is or is not a control side problem.

 

[no704]

85 and 86 are the field coil. If energized this connects 30 to 87. If not 30 and 87a are connected.
If 85 and 86 are +. The car may be switching ground. Jump 30 and 87 see if it turns on.

 

[Trucklord]

85 and 86 are the field coil. If energized this connects 30 to 87. If not 30 and 87a are connected.
If 85 and 86 are +. The car may be switching ground. Jump 30 and 87 see if it turns on.

Thanks for the reply.

Here's my process

1.Relay removed from socket.
2. I have attached the black multimeter wire to battery negative.
3. with multimeter red wire touching terminal 30 on the relay fusebox socket I get 12v on the multimeter
4. with multimeter red wire touching terminal 85 on the relay fusebox socket I get 12v on the multimeter
5. with multimeter red wire touching terminal 86 on the relay fusebox socket I get 12v on the multimeter
6. I would have thought 85 OR 86 would have been GROUND - after 12v passed through the coil ( coming through 85 or 86 - whichever is correct?

7. I removed the cover from the relay and popped it in the socket.
8. I manually pressed the coil arm to complete the circuit from 85 to 86 and then got 12v to the rear demister terminals ( red lead in one - black lead in the other connectors in demister wiring.
9. I have now removed the whole switch cluster assembly from the dashboard - so no switch even attached but still get the same results as above ?
10 - I have a new assembly coming today and did not want to plug it in, in case it blows something and breaks the switch.

My MAIN question is:

Should there be 12v power at the demister fuse box socket all the time on 30, 85 and 86 ?

Thanks
Eric

 

[Trucklord]

85 and 86 are the field coil. If energized this connects 30 to 87. If not 30 and 87a are connected.
If 85 and 86 are +. The car may be switching ground. Jump 30 and 87 see if it turns on.

Thanks for the reply.
Could you explain the car may be switching ground please?
In regards how that may be correct ? - or a fault ?

Thanks

 

[BillK]

Have you checked to see if the ground wire is good at the relay socket ?

My service documentation does not show a Sorento in 2010. How about a VIN ?

 

[Trucklord]

Have you checked to see if the ground wire is good at the relay socket ?

My service documentation does not show a Sorento in 2010. How about a VIN ?

Hi
There is no ground wire at the socket - I am absolutely sure there should be. Either 85 or 86 but there isn't.
By chance I also just came across this anomaly. In the socket when you bridge pin 30 to pin 85 another relay clicks - it is the relay for the front screen I think ( it has a zig zag image in the fuse box cover ).
Why on earth that would happen is beyond me as well.


Is anyone with a 2010 , 2011, 2012 sorento able to just check the relay socket on their car please and see if there is a ground on either 85 or 86 ?

Thanks

 

[RPH]

When using transistors as switches the designer has a choice to make. High side or low side switching. In simpler terms in more about the transistor in the circuit. If high side, then the transistor controls the power fed to the device. On low side switching, the transistor controls the ground side of the circuit. You could see potential right up to that transistor lead. But without a gate signal to turn the low side transistor on, then no operation. Low side switching is very common.

 

[BillK]

Hi
There is no ground wire at the socket - I am absolutely sure there should be. Either 85 or 86 but there isn't.
By chance I also just came across this anomaly. In the socket when you bridge pin 30 to pin 85 another relay clicks - it is the relay for the front screen I think ( it has a zig zag image in the fuse box cover ).
Why on earth that would happen is beyond me as well.


Is anyone with a 2010 , 2011, 2012 sorento able to just check the relay socket on their car please and see if there is a ground on either 85 or 86 ?

Thanks

TL,
I just looked at the wiring for a 2012 Sorento and the Rear Defroster relay wiring is sort of convoluted. It goes through an "HTD" module and to several other sources. You said yours is a 2010 so I dont know if its the same or not. If you want to post the vin I will get correct the wiring diagram for you but it might be later this afternoon. I think that is the only way you can properly troubleshoot this.

 

[Trucklord]

TL,
I just looked at the wiring for a 2012 Sorento and the Rear Defroster relay wiring is sort of convoluted. It goes through an "HTD" module and to several other sources. You said yours is a 2010 so I dont know if its the same or not. If you want to post the vin I will get correct the wiring diagram for you but it might be later this afternoon. I think that is the only way you can properly troubleshoot this.

I have PM'd You.
Thank YOu

 

[no704]

Thanks for the reply.
Could you explain the car may be switching ground please?
In regards how that may be correct ? - or a fault ?

Thanks

It depends. 30 is the load input, so probably + all the time. 85 and 86 must be one + and one - for the relay to turn on. Usually doesn’t matter what one, some relays have a diode built in to collapse the field of the coil faster, in this case the polairaty matters. If you have + to 85 and 86 with the relay removed, the switching system supply’s - when it wants to turn on. (Or should in your case).

 

[Trucklord]

It depends. 30 is the load input, so probably + all the time. 85 and 86 must be one + and one - for the relay to turn on. Usually doesn’t matter what one, some relays have a diode built in to collapse the field of the coil faster, in this case the polairaty matters. If you have + to 85 and 86 with the relay removed, the switching system supply’s - when it wants to turn on. (Or should in your case).

Thanks for the clarification.
However, I agree 30 seems to be the load input and + all the time, but both 85 and 86 are + all the time as well.
Very Odd.
I have been sent a schematic from a different sorento for the rear demister / defroster and heated mirrors and it is pretty extensive where the wires go to. I will study tomorrow again. It's 11:34pm here now.
Thanks.

 

[no704]

Good luck, one should go - on demand.
Worst case, now you know enough to just install a switch and abondon what ever system the car is using. I can’t think of any reason an oem would want to have this system disabled?

 

[Trucklord]

Good luck, one should go - on demand.
Worst case, now you know enough to just install a switch and abondon what ever system the car is using. I can’t think of any reason an oem would want to have this system disabled?

I have thought of doing just that. Fit a switch to make it work independently - like old school upgrades.

 

[exranger06]

The voltage you're seeing is probably bias voltage from whatever computer module that controls the relay. Inside the module is a "sensing" circuit that will tell the module if the relay actually turned on or not. This sensing circuit will have voltage on it if there is no current flowing. If the relay is installed and working, and there is current flowing (complete circuit) it will show 0V.
This is why multimeters are oftentimes a bad tool to use for troubleshooting. They have their place, but an incandescent test light is a far more useful tool. In order to troubleshoot accurately, you need to recreate what the circuit normally does. The circuit normally has current flowing through a relay. So when you're troubleshooting, you need to have roughly the same amount of current flowing through the wiring. A multimeter has a LOT of resistance and will have almost no current flowing when connected, which will mislead you. This is also why you want to use an incandescent test light, NOT an LED test light.

Connect a test light to battery negative, and probe pins 85 and 86. I bet it only lights up on one of those pins (that would be the positive side of the coil). Even though both have voltage when nothing is connected, the test light will pull the bias voltage on the negative side to ground. A light will not light up if both sides are connected to ground. Next, connect the test light to battery positive and probe the negative side again. The test light should light up then. Switch the defroster on and off. The test light should turn on and off accordingly.