9-7x headlight wiring

dgsaab

Registered Member
Original poster
Jun 28, 2016
26
MI
This is for 2009 9-7x, not sure it applies to other years/versions.

I don't have the official GM diagram, but I looked at several other diagrams online. They all show the HDM driving the low beams, acting as a (modulated) low beam relay. Seems normal. However, looking in my fusebox I have the HDM AND high and low beam relays. The back of the cover confirms with both graphics and text.

Does anyone have a GM diagram that shows this arrangement? Why would it need a relay in addition to the HDM?
 

TollKeeper

Guru
Dec 3, 2011
6,886
Brighton, CO
The headlights are pulsed to provide only 60% during daytime running lights (DRL) operation.

What exactly are you trying to accomplish?
 

dgsaab

Registered Member
Original poster
Jun 28, 2016
26
MI
I'm trying to understand the circuit and acquire the correct diagram.

Yes I understand what the HDM does. As I mentioned in the op it provides a pulse width modulated voltage ( I believe 70%) to the headlights in DRL mode and 100% in normal "on" mode. The HDM is itself a solid state relay, so shouldn't require another relay.
 

TollKeeper

Guru
Dec 3, 2011
6,886
Brighton, CO
A relay couldnt survive the switching, which is why the HDM is there.

On my Envoy, I just put a diode in at the rear BCM which puts the DRL at full power.
On my 9-7x 5.3i, since it had factory HID, it uses the orange corner lights for the DRL, and they arent pulsed.
 

Mooseman

Master Blaster
Moderator
Dec 4, 2011
22,548
Ottawa, ON
Time out here.

First question is, do you a 4.2 or 5.3? This will say if you have halogen or HID lights. I know for sure the HID (5.3) uses the turn signals as DRL. I'm not entirely sure if the halogen (4.2) also uses the turn signals or the headlight bulbs.
 

TollKeeper

Guru
Dec 3, 2011
6,886
Brighton, CO
He has a 4.2 according to his signature
 

dgsaab

Registered Member
Original poster
Jun 28, 2016
26
MI
Yes, 4.2 with halogens used for DRL. If anyone has a diagram they believe is correct, please post it and I can show you exactly what the issue is. Otherwise we're going around in circles.
 

Mooseman

Master Blaster
Moderator
Dec 4, 2011
22,548
Ottawa, ON
If it's halogens, then it should be the same as other gmt360. Schematics are available in the manuals download. The link is in my signature.
 
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dgsaab

Registered Member
Original poster
Jun 28, 2016
26
MI
Ok, here is the diagram from your link. Notice how the HDM feeds the low beams and there is no low beam relay. The HDM performs the relay function.
In my car, I have BOTH an HDM and a low beam relay (#63). I can find no diagram that shows both, nor can I think of why you would need both.
Capture.JPG
 

TollKeeper

Guru
Dec 3, 2011
6,886
Brighton, CO
Have you tried pulling the relay and seeing if everything operates correctly?
 

dgsaab

Registered Member
Original poster
Jun 28, 2016
26
MI
I have. With ignition key out, if I pull the HDM headlights don't work. If I pull the relay out they still work. But that's just one set of conditions. I cannot assume GM put a relay there for no good reason.
 

Mooseman

Master Blaster
Moderator
Dec 4, 2011
22,548
Ottawa, ON
It's quite possible that the headlight relay is of no use and somebody just shoved one in there for no reason. Sometimes the OEM will have empty slots for relays and fuses that don't apply to your particular vehicle or options. You might notice there aren't any contacts inside that relay socket.
 

dgsaab

Registered Member
Original poster
Jun 28, 2016
26
MI
I've considered that possibility and dismissed it because:
1. The lid of the box has a pictorial and list of relays and fuses. It correctly shows and lists all populated relays and fuses and does not show anything in the unpopulated locations. The lid also has Saab printed with the list so it is not generic.
2. The relay is exactly like the rest of the small grey relays in the fuse box, it is OEM and has the same identical markings as all of the rest of them. It would be practically impossible for an owner to find years later a relay from the same production run. And go through all the trouble for no reason.
3. I found on eBay a random 2007 9-7x fusebox and the picture clearly shows it has both HDM and low beam relay. It's different from mine only because it has the second solid state relay for the fan. It also has the pictorial that accurately shows all relays and fuses.


The only remaining possibility I can think of goes something like this:
The diagram above is not correct for the 9-7x. In all fairness it does not list the 9-7x, although it does list the Ascender. Perhaps that's a clue. And it would imply that the 9-7x has a different headlight circuit from the rest of the GMT360 trucks, which is my main concern.

Edit: It would be interesting to hear from another owner if they have both the HDM and low beam relay in their fusebox. Only takes 30 seconds to check.
 

TollKeeper

Guru
Dec 3, 2011
6,886
Brighton, CO
The headlight circuit for sure is different on the 9-7x with a 5.3. I will compare the 9-7x 5.3 I have to my Envoy 5.3 when I get home.. Working on it tonight anyways.
 

mrrsm

Lifetime VIP Donor
Oct 22, 2015
5,984
Tampa Bay Area
In addition to whatever might be going sideways within the Under-hood Fuse Box and the unique Head Lamp Relays... There may also be a Headlamp Weather-Pack Harness Connector issue involving a corrosion problem.

The increase in the electrical resistance corrosion always brings can cause the wiring to Overheat, then Melt or Weaken the Plastic Connector enough to cause it to Fracture ...thusly:

SAAB97XHEADLIGHTCONNECTOR1.jpg

Now even though Saab no longer offers the OEM replacement connectors, GM - ACDelco has a version available as a Splice-In Weather-Pack Kit that should be a decent alternative for this repair... thusly:

SAAB97XHEADLIGHTCONNECTOR2.jpgSAAB97XHEADLIGHTCONNECTOR3.jpg

@Realism 's Epic Thread on All Ground Wire Locations for GMT360s is another resource to compare all of his Imagery to your SUV and then inspect your Saab Bonding Straps for any looseness or corrosion issues as well:

 

dgsaab

Registered Member
Original poster
Jun 28, 2016
26
MI
In addition to whatever might be going sideways within the Under-hood Fuse Box and the unique Head Lamp Relays...
Thanks. You bring forth some very useful general info. However, there isn't anything going sideways with any of those components on my truck, it all works as intended. I just want to have a wiring diagram that shows the wiring correctly for the 9-7x. And also curious as to why both an HDM and low beam relay are necessary.
 
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