Hello everyone, hoping someone can help me out with my truck. My issue is every light in my truck flashes after my gm alternator swap. I put a fleet wood Cadillac alternator running 140 amps. The lights will be flashing as soon as the turn on,( I mean my dash,tail lights, and headlight lights). when I hit my breaker for the alternator it seems to go up in idle a tad bit and my lights will be fine. Werid issue for me been having problem after problem lately for the past 3 weeks. My battery is good. Looking for some extra help can't find anything on flashing lights. Appreciate the time and any advice anyone has. Thanks

 

That is a strange one .

By chance do you have a alarm or parts of one .

Do the lights flash completely off and on??

Go from dim to bright ??

Have you checked the output of your alternator ??

It comes down to the alternator or something you may have done in the install.

When the alternator is taken off line it reduces the load on the engine so some increase in rpm might be noticed.

Just how much increase in rpm are you getting??

What other electrical loads are you using to need this higher output

 

So my truck lights flicker as soon as they turn on. Not on and off but flash while on. As I said it's every light in the truck. Out out on battery is good and when I put the alternator in is was running where it should. I have a sub in my truck. I can't try disconnecting it to see if that helps. However I followed 4x4 crawlers forum while installing the alternator with a friend who has done in his 88 forerunner and he's has no issues for 1000 miles. The truck has no alarm. If it help I removed the ac belt to the truck never used it. And for the idle seems to run better without the alternator hooked up. I have one more problem to check when I get home and to test the output on the alternator. It has just baffled me . Feels like I'm running in circles right now.

 

So far I have tested the amprige the alternator is running 15-16.3. Hit the breaker runs steady at 15 volts. I thought my battery light would come on if I hit the breaker it has not. Also while the breaker is flipped off my lights do not flash anymore

 

none of that makes sense.

you can't test alternator amperage output with a multimeter, what you are probably doing is checking the voltage, and you should be doing that at the battery terminals first.

you didn't tell us what breaker you are messing with, and i'm not aware of any breaker that can be turned off and on like you are describing... there is however at least one breaker that will trip when something is shorted out, but you can't turn it off and on at will.

 

The breaker has a switch on it. I've never messed with electrical before, never liked it. The alternator has an international regulartp but still when I turn on my lights they will start to flicker.

 

If you are getting 15-16 VOLTS at idle you are over-charging your battery. this will eventually cook off the fluid and ruin your battery as well as burning out headlights before their time. I put a gm one wire alternator in a 1980 Yota pickup that I used for a hunting buggy and had the same charging issues, I didn't notice the lights flickering though. I fixed it by building my own voltage regulator with some ignition resistors and a relay. with some trial and error I found a resistor combination (different values) in parallel that gave me around 14.2 volts at idle. the relay was hooked up to bypass the resistors when I turned the headlights on. it wasn't pretty, but it was easy and dependable. I no longer have the truck so I couldn't give you any specifics on what I did other than what is stuck in my dusty old brain.

 

it sounds like you have a bad diode in the alternator and it's putting out AC instead of DC. Is this a used Alternator? some parts stores have alternator test benches or portable in-car testing devices. Go have it tested to be sure you have a good Alternator to start with (even new ones are junk sometimes).

 

I had it tested today it is the regulator in the alternator. Thanks for all the replies I'll have to look into how I go about finishing this. Might go wih safari 105 amp alternator.