Question about 2004 Chevrolet Silverado 1500 Crew Cab

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How to remove #45 cooling fan relay

How to swap #45 cooling fan relay and #46 headlight driver module

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The relays just pull out of the socket.

Posted on Oct 24, 2012


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SOURCE: Low Beam headlights not working

The daytime running lights run the high beam bulbs at low voltage so it sounds like you need to put the relays back where they were and either replace the low beam bulbs or repair the wiring to them.Also the relay you removed could be defective.

Posted on Dec 28, 2009

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How to replace relay module 45

Relay module 45 ? You mean relay # 45 in the under hood fuse / relay power distribution box. It's just a relay , not relay module ! Having problems with your cooling fans ?
45 FAN Relay Engine Cooling Fan. If so it just pull's out , wiggle an pull

Oct 20, 2015 | 2004 Chevrolet Chevrolet TrailBlazer LS

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I have no low beam headlights. already checked bulbs, fuses, relay and dimmer switch. can you help?

Before you replace the #46 HDM relay (in the fuse block under the hood) try exchanging it with the #45 cooling fan relay and see if your low beam lights work. If they do, the HDM relay (actually solid state module, not a relay) is bad.

Jul 30, 2014 | 2004 GMC Envoy

1 Answer

2002 trailblazer headlight

Try swapping relay #45 & 46 in the underhood fuse panel as a test. Relay #45 is for the low beams. Also check the headlight bulb connectors for signs of overheating.

Dec 14, 2012 | 2002 Chevrolet TrailBlazer

1 Answer

My low beam headlights won't turn on in 2004 gmc envoy

It's the headlamp relay #46. If you want to test it, swap it out with the cooling fan relay #45 and see if your headlights work. If they do you know this is the fix. Found the solution online a couple of years ago and it was spot-on. The part was $45 at autozone at the time.

Aug 12, 2012 | 2004 GMC Envoy

1 Answer

The dark interstate late at night is not the time to loose your headlights. I checked the fuses and the bulbs. Last time this happened, which was about 2 years ago, I had to have the day runner sensor...

Swap relay #45 & 46 in the underhood fuse panel. Relay #46 is for the low beams, #45 is for fan clutch. If this does not cure it, did you try setting the headlight switch to the Headlamps position? Make sure you checked the correct fuse as well, it is #6 in the underhood fuse panel.

Sep 20, 2011 | 2004 GMC Envoy

1 Answer


Your question simply said headlight problems. So I am going to assume, since it is a 2004 model, that your low beam headlights quit working. If that is the case, here is a possible solution. In the fuse box under the hood,, you will find what looks like a relay. It will be marked HDM #46. Swap HDM #46 with HDM#45 and see if the low beams come on. If they do come on, you need to replace HDM#46 with a new one, which you will probably have to get from the dealership. Be sure to swap the two back in to their original positons because HDM#45 controls the cooling fan.

Dec 06, 2010 | 2004 Chevrolet TrailBlazer

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2003 gmc Envoy Low Beam Headlights both quit at the same time. Checked fuses and replaced bulbs. No dice. ????

Relay in fuse box under hood on driver side wheel well labeled HDM, #46 on 2004 Envoy XUV. Swap with relay #45 labeled "Fan" to test. That was my problem.

Good Luck,

Jul 01, 2010 | 2004 GMC Envoy

1 Answer

The Saturday before Easter I was doing last minute shopping,when i got in the car to leave my headlight wouldn't work.The parking lights and high beams work, I changed the bulbs that didn't work. I got in...

Try temporarily swapping #45 Cooling Fan relay and and #46 HDM relay in the under-hood fuse block, and see if the low beams come on.

The one originally in the HDM #46 socket is bad. That relay is actually is a solid state module, not a conventional relay, and will cost you anywhere from $25-45 at the dealer.

HDM = Headlight Driver Module

Also known as a solid-state relay, since instead of relay contacts and a coil, it uses a power switching transistor capable of running the headlights (and the fan clutch in #45) at less than 100% power, to provide daytime running lights, and control the fan clutch engagement for the engine cooling fan.

Thank you for using fixya and be safe.

Apr 16, 2010 | 2006 Chevrolet Trailblazer

1 Answer

Highbeams work but low beams wil come on regardless of the settings. Chcked fuses and they are fine.

Check the relay #15016745 in the under hood fuse box. It is in position 46. There are actually two of them side by side, one for the low beams and one for the cooling fan. Swap the two relays and see if the headlights work, if so you have found the problem. Swap them back and purchase a replacement relay. The dealer should have them for around $45, other parts stores may have them or you may find them on ebay by searching for 15016745.

Feb 28, 2010 | 2004 Chevrolet TrailBlazer

2 Answers

Low beam headlights

Try swapping #45 cooling fan relay and #46 HDM (headlight driver module) relay in the underhood fuse block. These are solid state modules and are not like conventional relays.

Oct 21, 2008 | 2004 Chevrolet TrailBlazer

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