NEW GM headlight relay (relay #46) GM part# 13506836

Chickenhawk

Hobbyist
Original poster
Dec 6, 2011
715
GM has just released a fix for the 2006-07 recall involving some GMT360s. It is a new headlight driver module (HDM relay), GM part #13506836. It replaces part #15016745 which could allow the headlights to cut out if overheated.

827a4ba0be5d46410ed2076428e53d97_zpsjhj6dngd.jpg


Our 07 Trailblazer was not recalled in Canada, and I cannot find this part for under $130 in the U.S., as opposed to $40 for the older relay.

Has anyone had this recall fixed with the new part yet? Up to about 3 months ago, GM had no fix for the recall and would only swap old relays for new 15016745 relays. Now, part #13506863 seems widely available (for a price) at dealers. I have not yet found it on Amazon.ca or Rock Auto.

I have been chasing our old flickering headlights issue with a few years, with no solution. I replaced alternator, relay and the big 3 wires; no change. I also recently had an aftermarket headlight relay (NAPA AR6100) fail at night, killing my headlights for 10 minutes.

I would be very interested in owners' experience with the new relay in the coming months.

If your relay did not fail, then replacing 15016745 with GM 13506836 will not affect anything (except make it more reliable and less prone to failure.) But I would like to know if this also cures the flickering headlight problem. I don't really want to invest $130 to find out it does nothing.

Has anyone had a Canadian 06-07 truck recalled for this issue? Heck, I would even pay someone in Winnipeg $20 if I could borrow the new part for two days just to see if it fixes the flickering issue.
 
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Mooseman

Master Blaster
Moderator
Dec 4, 2011
21,832
Ottawa, ON
I wonder what changed from the 02-05 TB's to the 06+ that would cause the relays to overheat/fail? I haven't had any issues with my 02 and it's the original relay. Have you tried an older relay? Maybe GM changed suppliers in 06?

To confirm it's a relay problem, why not just use a piece of wire on the two contact terminals in the relay socket? If the headlights don't flicker, then the relay is the issue.
 
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coolasice

Hobbyist
Oct 27, 2013
977
Northern Maine
GM has just released a fix for the 2006-07 recall involving some GMT360s. It is a new headlight driver module (HDM relay), GM part #13506836. It replaces part #15016745 which could allow the headlights to cut out if overheated.

827a4ba0be5d46410ed2076428e53d97_zpsjhj6dngd.jpg


Our 07 Trailblazer was not recalled in Canada, and I cannot find this part for under $130 in the U.S., as opposed to $40 for the older relay.

Has anyone had this recall fixed with the new part yet? Up to about 3 months ago, GM had no fix for the recall and would only swap old relays for new 15016745 relays. Now, part #13506863 seems widely available (for a price) at dealers. I have not yet found it on Amazon.ca or Rock Auto.

I have been chasing our old flickering headlights issue with a few years, with no solution. I replaced alternator, relay and the big 3 wires; no change. I also recently had an aftermarket headlight relay (NAPA AR6100) fail at night, killing my headlights for 10 minutes.

I would be very interested in owners' experience with the new relay in the coming months.

If your relay did not fail, then replacing 15016745 with GM 13506836 will not affect anything (except make it more reliable and less prone to failure.) But I would like to know if this also cures the flickering headlight problem. I don't really want to invest $130 to find out it does nothing.

Has anyone had a Canadian 06-07 truck recalled for this issue? Heck, I would even pay someone in Winnipeg $20 if I could borrow the new part for two days just to see if it fixes the flickering issue.
Msrp for the relay is $200. $130 is not a bad deal in that case... I don't know what's inside the relay that's worth that price, but that is the going rate for them. Have you tried the online recall check on GMs website?
 

cornchip

Hobbyist
Jan 6, 2013
567
06/07/08 TB's all have RVC style alternators. Would temporarily pulling the 2 pin plug cause the alternator to charge steady at the default (13.8V and no pulsing)?. And, could a low charge rate be enough to strain an already marginal relay (amp draw is higher with low voltage) and cause it to fail? Seems like a heavy duty relay is masking a problem, unless it really needed a better relay all along. My 2007 has the problem relay with no issues....yet. For 130 US...I'll pocket a few used ones at the wrecking yard and keep em in the glove box for a dark night.
 
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OP
Chickenhawk

Chickenhawk

Hobbyist
Original poster
Dec 6, 2011
715
I wonder what changed from the 02-05 TB's to the 06+ that would cause the relays to overheat/fail?
I think cornchip may be on to something when he points out that the new regulated voltage control alternator on the 06+ might strain the stock relay, and this is why the recall has only affected 06 and 07.

To confirm it's a relay problem, why not just use a piece of wire on the two contact terminals in the relay socket? If the headlights don't flicker, then the relay is the issue.
Would this work? I am not an expert at electrical systems. It seems like a very easy thing to try. Off hand, can someone tell me which terminals to jumper to try this? I know the relay has a diagram on it, but my eyes don't see small things very well anymore. What is the down side? Will this melt something? Otherwise, all we would have to do is carry a small jumper wire in our glove box in case the headlights fail at night, instead of the extra relay (and now, two relays, for me) in the glove box.

Has anyone ever tried this?
 

Mooseman

Master Blaster
Moderator
Dec 4, 2011
21,832
Ottawa, ON
Only wire that would melt is the jumper wire so you should make a good one made with actual terminals and a good gauge wire. And you'll have to pull that wire when you turn off the truck or they will stay on.

It is a solid state relay so that the DRL will work with the PWM from the BCM. Maybe use a capacitor to get rid of the PWM and use a regular relay.
 
OP
Chickenhawk

Chickenhawk

Hobbyist
Original poster
Dec 6, 2011
715
I will let you know how this works. Can anyone tell me the exact terminals to jumper? All I need is to jumper them for ten minutes at night and I will know right away.
 

Mooseman

Master Blaster
Moderator
Dec 4, 2011
21,832
Ottawa, ON
I think you're gonna have to get out the magnifying glass :eek:
 

budwich

Guru
Jun 16, 2013
1,719
kanata
I think the picture that you posted has all the information that you need... even without your glasses on.... :smile:
 

freddyboy61

Active Member
Dec 4, 2011
265
Terminals 2 & 4

BTW - this is not a relay, it is a electronic module that produces a PWM (pulsewidth modulation) signal to operate the DRL. That is how the low beams are dimmed down for daylight operation and full on for night operation.
 
OP
Chickenhawk

Chickenhawk

Hobbyist
Original poster
Dec 6, 2011
715
You guys are hilarious. I look at that diagram and it could be hieroglyphics.

As near as I can figure, pin 4 (the middle pin in the 3-pin array) goes to lights. With the relay activated, power flows from pin 2 (the top pin in the 3-pin array when looking down from above, or closest to the engine) to pin 4. What confused me was the diode between 2 and 4, and the fact that I got a bit of resistance between 2 and 4 when testing the relay itself, whereas a normal mechanical relay would have 0 resistance. (I am easily confused by lectronics.) Thank God for my magnifying glass app on my iPhone. I could not have seen those tiny numbers beside the pins with Superman's eyes.

So my plan is to jumper from 2 to 4 (the top two pins) and then as a final test, jumper straight from 12 volt battery to pin 4.

I will let you know.

And, by the way, THANK YOU to everyone. Even the smart ass ones. (I love all you guys.)
 

cornchip

Hobbyist
Jan 6, 2013
567
So terminal #5 is pulsed before the module by some other pcm/bcm? I have a schematic that does in fact call it a relay (wish it was easier to read)....but controlled by PWM it doesn't say. End of the day....it's the coil or the solid state equivalent to a coil that packs it in....correct?

large.jpg
 

DAlastDON

Guru
Apr 6, 2014
5,550
Kentucky
From the schematic on the headlight module i would assume its an opto-coupler and a triac inside the packaging.
 

MAY03LT

Founding Member
Nov 18, 2011
3,412
Screenshot (157).png
So my plan is to jumper from 2 to 4 (the top two pins) and then as a final test, jumper straight from 12 volt battery to pin 4.

You got it.

So terminal #5 is pulsed before the module by some other pcm/bcm?

Yeah the bcm controls the signal to the hdm. IIRC 100% duty for low beam, 70% for drl/perimeter lighting (roughly 2v less).
 

C-ya

Hobbyist
Aug 24, 2012
1,098
So on the pre-'06 models that have a lighting issue, it's just the module failing? It failed on my '05 last summer.
 

Mooseman

Master Blaster
Moderator
Dec 4, 2011
21,832
Ottawa, ON
If you mean the "relay", yeah, it's a common failure part. It's the same as the fan relay if you want to switch them as a test too.
 

C-ya

Hobbyist
Aug 24, 2012
1,098
Yeah, I just used their term, but it appears they call it a module relay. So I guess we are both correct.
 

stvrob

Registered Member
May 28, 2014
137
I have an '06 Trailblazer EXT with the headlight relay problem and I cant get GM to acknowledge the recall.
 

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