Help me fix my heated seats please

Hello,

Trying to fix the heated seats in my 91 Rivage.
No click from relays when turning heated seats on with ignition on and obviously seats not heating up.

So I pulled out the old relays which looked the the below and figured they were obviously shot.

Ordered some tested ones from a MK3 convertible (same part number) fitted theM but still no click and heat.

So I got the multimeter out and got a reading of about 25.5V between port number 8 and 7 in the relay with just the ignition on and then when I turned the heated seats on I got the same reading also between port 6 and 7.

So whilst I don’t know if those readings are good there seems to be juice getting to the relay and the switch seems to be doing it’s job.

Now I’m stuck as to what to try next… I’ve disconnected the white connector switch between the relay and the seat circuit and first thing I wondered whether it was correct that 4 pins were attached to one side of it and 2 pins to the other side

Anyway, could someone help guide me as to what to try next please and whether the reading I’ve got above make sense or are good / bad?

I don’t really know how to test the relays themselves but they are clean and I have no reason to believe they wouldn’t work (especially since I tried both on both seats with the same result.

On a side note, which I don’t know if it’s important but when I disconnected the old rusty relays I somehow managed to short the circuit out and had to replace the fuse…. Don’t know if it’s relevant as I seem to be getting power to the relay.

Thanks,
Ben

I would fix the Water leak that corroded the relays, to prevent a re-occurence.

A divide and concur approach works well, as in.

1. Use the heated seat diagrams in the Bentley or Haynes to see where you are.

Pre 90



91 and above


Your statement of 25V between pins 7 and 8 are wrong, as 8 is input voltage 12V and 7 is ground.  As you can't really step up a DC voltage with out a Circuit between them I would ask was it in the proper Scale as in Ohms vrs Volts.

I kind of agree that the relays are toast, but Elements do go bad.  So if the Corroded relays (Heater Control Units) do more than a relay, didn't blow the Fuse or melt the switches on the Dash, I would suspect the Heater Elements be tested to Verify that they didn't open up.

Brian, you are correct sir - the reading is 12V not 25 - my bad for turning the multimeter dial the wrong way!

So I’ve got power to the relay - would the relay not still switch on and off even if the heat elements themselves had gone bad?

I figured it should just switch when triggered with power but as you can tell this isn’t exactly my forte!

Thanks,

Ben

One more q for testing the relay.
Am I right in thinking that energising 86 and 31 should open/close the circuit and that a closed circuit should read no resistance between H and 15?

I’m just a bit confused by having 6 pins!

That is a IC (Integrated Circuit) controlled relay.



If you look at it, there are 6  pins to control it
3 are Ground and power.
3 are control or sense inputs.

The output pin is 15, and that is 12V+ from pin H

So if you place 12+ on the pin of the connector (H) it should power the heating coil to the seat

Pin 4/T is the sense from the seat cushion Input
Pin 7/31 is ground Input
Pin 6/P is The regulation from the roller switch Input
Pin 5/86 is 12V+ in from roller switch to engage the relay input power to circuit
Pin 8/15 is fused 12V+ to main relay contacts Honking Voltage to power seat heaters
Pin2/H is the output 12V+ to the seat heaters Honking power out to the seat heaters from the switched on relay

So when you turn the rocker switch from off to on, current flows from ground  pin 7/31through the ic to pin 5/86 that turns on the relay that applies power to the heaters via pins 8/15 in  to 2/H out.

The integrated circuit regulates the on/off of the relay
depending on the Position of the roller switch pin 6p
And monitors the Temp of the heating units via the seat temp sensor on 4/T

Since I don't have the IC number, nor the diagram of the innards…This is as close to the specifics that I can get, but maybe RubJohnny can get closer.

Oh yes, Basic electrionics Current flows (POWER) and Voltage is a measure,  I liken it to a river.  Putting your finger in it tells you how hot or cold it is, but the force of the water tells you how much current is there.

We Measure Current in Amps and the Voltage is a spot check of it.  Anything (inductor, Capacitor, Wire, Diodes, Resistors integrated circuits), are the point where we can measure Voltage to see if the River or Current is flowing.

All Electrics has to Obey Ohms law, that is Electromotive
Fource expressed as "E" is equal to Resistance measured in OHMs expressed as R times the Amperage Expressed as I.  E=IxR.  Nothing escapes it, it is the LAW of circuitry.

Oh, and I forgot that when you violate it, you will be amazed at how much Smoke is stored in the Insulators on Wires, IC's, and other bits.   I have only one other thing to add.



Enjoy.

I have a Basic Electrical Primer Link in my how-to's in the archive section (click my link in the signature then scroll down to the electrical section.)

Thanks Brian, this is very detailed and I’ll read it again in the morning with a fresh mind and the circuit in front of me.

What I’m not quite clear on yet is whether the relay would be prevented from opening / closing when energised if the circuit it’s controlling is broken I.e. should I still hear the relay click even if the heater elements were dead?

What I’m not quite clear on yet is whether the relay would be prevented from opening / closing when energised if the circuit it’s controlling is broken I.e. should I still hear the relay click even if the heater elements were dead?

If the roller switch is putting 12v on Pin 5/86 of the controller, that with a good ground on pin 7/31 should Turn the relay on.

You can test the relay by placing 12V+ on pin 5/86 and ground on 7/31

This will eliminate the roller switch. and the relay should click….

A 9v DC battery will do this out of the circuit as well.

Do the test out of the car, as the heating element doesn't have to be in the circuit to energize the controller to cause the relay to turn on or click.

Thanks Brian! Will test and report back