I'm now on my third flasher module in my GMC Sierra in less than 2 years. The last time, my mechanic checked all the related wiring and even replaced all the TV turn bulbs because it's just crazy to have 2 fail in 2 years. He also suggested the problem may be in my trailer.So, I have a Prowler trailer. I inspected the wiring and fixtures and saw no evidence of shorts, etc. But I did notice one thing: this trailer has 3 lamps on the left and 3 on the right, so when the hazards are on that's 6 bulbs flashing, for a total of 11 amps, plus whatever the truck's flashers use. So could this just be too much power for the flasher unit, causing it to burn up?Do most trailers use less than this many lamps for the turn/hazard indicators?Maybe I should replace them with Led equivalents to cut way back on the amperage?Because I'm going camping next weekend, as a temporary measure I removed one of the 3 bulbs on each side and will also try to avoid using the flashers (the left or right turn signals would only use half the power of the flashers I'm guessing).

It could be the flashers that are being installed. Normal flashers cannot handle that big of load.Your profile does not show year of your Sierra. It would be good to know that to research whether yours have an available heavy duty flasher.Do you have trailer package? You could look under the hood for those fuses. The trucks wiring works relays under the hood fuses and relay panel. These only work if the truck has towing package and the trailer is connected to those wires rather then being tapped off truck's lighting wiring.You will get a lot of input about switching to LED lamps.

I know next to nothing about vehicle electricals, but I do remember that when U-haul wired my vehicle for trailer lights etc, the lights themselves were connected at the rear of the vehicle, and they put in what they called a "heavy duty flasher" back there since according to them the regular one wouldn't handle the load.

count the number of bulbs that could be flashed at one time and buy a flasher that is rated to flash that many bulbs. Most parts stores have them

enblethen wrote:It could be the flashers that are being installed. Normal flashers cannot handle that big of load.Your profile does not show year of your Sierra. It would be good to know that to research whether yours have an available heavy duty flasher.Do you have trailer package? You could look under the hood for those fuses. The trucks wiring works relays under the hood fuses and relay panel. These only work if the truck has towing package and the trailer is connected to those wires rather then being tapped off truck's lighting wiring.You will get a lot of input about switching to LED lamps.It's a '08 2500HD. I bought it used from a dealer; supposedly the previous owner towed a double horse trailer with it but that doesn't necessarily mean it has the officlal towing package. How would I check for this?Since I just had the flasher module replaced at my mechanic I don't think I will be replacing it right away. I will see if it happens again, and next time will insist on a heavy duty flasher (unless I switch to LED bulbs first). The mechanic did not tell me that was an option.

truck's flasher module keeps burning out; trailer's fault?

19 Replies

enblethen
Nomad
Jun 08, 2014
I just through some info into O'reilly auto parts and came up with these.
Flashers
I ask the OP earlier to post year of his truck but haven't seen anything back.
My MH uses the old two pin style found in many rigs. I replaced the bi-metal unit with a soild state one many years ago. Electronic flasher
down_home
Explorer II
Jun 08, 2014
enblethen wrote:
It could be the flashers that are being installed. Normal flashers cannot handle that big of load.
Your profile does not show year of your Sierra. It would be good to know that to research whether yours have an available heavy duty flasher.
Do you have trailer package? You could look under the hood for those fuses. The trucks wiring works relays under the hood fuses and relay panel. These only work if the truck has towing package and the trailer is connected to those wires rather then being tapped off truck's lighting wiring.
You will get a lot of input about switching to LED lamps.

x2 Don't know much about Chevys but on Dodge and Ford that is usual. they all plug in, or did, just alike. The larger unit for RV or truck is physically larger. On a Dodge I had I had to use a drop of silicone glue to hold it in. It was larger than stock Dodge Truck, to aid boat trailer.
down_home
Explorer II
Jun 08, 2014
enblethen wrote:
It could be the flashers that are being installed. Normal flashers cannot handle that big of load.
Your profile does not show year of your Sierra. It would be good to know that to research whether yours have an available heavy duty flasher.
Do you have trailer package? You could look under the hood for those fuses. The trucks wiring works relays under the hood fuses and relay panel. These only work if the truck has towing package and the trailer is connected to those wires rather then being tapped off truck's lighting wiring.
You will get a lot of input about switching to LED lamps.

x2 Don't know much about Chevys but on Dodge and Ford that is usual. they all plug in, or did, just alike. The larger unit for RV or truck is physically larger. On a Dodge I had I had to use a dro pof silicone to hold it in. It was larger than stock Dodge Truck, to aid boat trailer.
wa8yxm
Explorer III
Jun 07, 2014
Changing to LED's is a very good option..

Flashers come in 3 types now days

One is a special "Module" that only fits your truck and alas if you have those you are in tribble, I can fix but your are in tribble.

The second is either a 2 or 3 wire flasher that is specific to the number of tail lights you have..

The third is the HD, 2 or 10, makes no difference, it works. IN fact it will work with just one lamp.. This is the one you want.

How to tell them apart. If you turn the signals on and the light comes on RIGHT NOW, you have the WRONG type of flasher

If you turn it on and the light comes on about a quarter to half second later
You have the RIGHT kind of flasher.

NOTE: This assumes an old mechanical flasher,, Modern solid state ones that will not apply.

IF you want to know why.. Ask.
solismaris
Explorer
Jun 07, 2014
enblethen wrote:
It could be the flashers that are being installed. Normal flashers cannot handle that big of load.
Your profile does not show year of your Sierra. It would be good to know that to research whether yours have an available heavy duty flasher.
Do you have trailer package? You could look under the hood for those fuses. The trucks wiring works relays under the hood fuses and relay panel. These only work if the truck has towing package and the trailer is connected to those wires rather then being tapped off truck's lighting wiring.
You will get a lot of input about switching to LED lamps.

It's a '08 2500HD. I bought it used from a dealer; supposedly the previous owner towed a double horse trailer with it but that doesn't necessarily mean it has the officlal towing package. How would I check for this?

Since I just had the flasher module replaced at my mechanic I don't think I will be replacing it right away. I will see if it happens again, and next time will insist on a heavy duty flasher (unless I switch to LED bulbs first). The mechanic did not tell me that was an option.
CA_Traveler
Explorer III
Jun 07, 2014
Or change the bulbs to LEDs.
othertonka
Explorer
Jun 07, 2014
count the number of bulbs that could be flashed at one time and buy a flasher that is rated to flash that many bulbs. Most parts stores have them
Francesca_Knowl
Explorer
Jun 07, 2014
I know next to nothing about vehicle electricals, but I do remember that when U-haul wired my vehicle for trailer lights etc, the lights themselves were connected at the rear of the vehicle, and they put in what they called a "heavy duty flasher" back there since according to them the regular one wouldn't handle the load.
enblethen
Nomad
Jun 07, 2014
It could be the flashers that are being installed. Normal flashers cannot handle that big of load.
Your profile does not show year of your Sierra. It would be good to know that to research whether yours have an available heavy duty flasher.
Do you have trailer package? You could look under the hood for those fuses. The trucks wiring works relays under the hood fuses and relay panel. These only work if the truck has towing package and the trailer is connected to those wires rather then being tapped off truck's lighting wiring.
You will get a lot of input about switching to LED lamps.

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truck's flasher module keeps burning out; trailer's fault?

19 Replies

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