View Full Version : 2001 C3500 HD Hazard Relay Location

White Gardens
09-04-2011, 12:31 PM
My hazards come on but don't flash. Before I replace the multi-function switch I'm going to try the relay first.

Basically I need to know the location or where to start looking for it.

The cab is the older body style so the location should be the same as a chevy silverado up to 2000.

Thanks in advance.

Impressions Landscaping
09-04-2011, 02:52 PM
The relay should be under the dash. Are you talking about the same relay that works the left and right turn signals? If it's that one, then it is under the dash near the e-brake pedal. Should be the bottom of the relay panel under there if I remember correctly. I'll take a look later on and let you know if you would like me too. Also, if your looking for it and your turn signals work, turn your signals on and you should hear a "click" coming from the relay. Just put your finger on it and you'll feel and hear the click.

White Gardens
09-04-2011, 03:16 PM

Ended up finding it, easier than expected.

Swapped out the relay with no luck. Probably the multi-function switch is the problem.

09-04-2011, 08:20 PM
This may sound like a dumb reply, but replace the all the signal bulbs (front/rear). Sounds like one bulb maybe out on both sides.

White Gardens
09-10-2011, 11:44 PM
Multi-Function switch was the culprit. Hazards work great now.

As a side note IMPRESSIONS, I know you take great care of your truck, so you might want to check out the rear auxiliary tank.

I had have problems with the rear tank not filling the front, and I have re-built most of the fuel system and when I got to the back I noticed the issue.

The rear sending unit had rotted enough to allow air leaks at the metal fittings. Basically I just grabbed the hoses and they broke off.

What has happened is that the venting for the tank seems to have plugged itself and the tank has collapsed in at the top, and I'm guessing when the temps dropped and the fuel condensed.

So now what has happened is that water and salt can't run off the tank like it should and rotted the sending unit. I'm either going to just stick a new unit in and paint it up good, or try to find a replacement tank so it doesn't happen again.


Impressions Landscaping
09-11-2011, 12:01 AM
White Gardens...thank you for the heads up...it's appreciated. Believe it or not, but about a month after I picked up my truck, it died....with about 1/2 tank of fuel. Couldn't get it to restart. The sending unit ended up being the culprit, it was rotted and I didn't notice, so I replaced that about five years ago. However, I keep some grease on it and keep it clean since its easy to get to with the dump body. I think it's a crappy design personally...why would GM manufacture a tank with a dip on top for water/sand/salt to sit on? My front sending unit is crusty and its time to replace that, but that also includes fuel lines as well....How's the truck doing??