2nd Gen Non-Engine/Transmission lights dim at idle

[**ICEMAN**]

warm engine(after being driven several miles) with head lights or just parking lights on and the truck in gear(auto) and foot on the brake and @ idle the amp gauge drops a little below 14 and the lights dim.

i put it in park and no foot on the brake and the amp gauge goes to just a hair above 14(normal) and lights are fine.

i turned the heater fan off,,radio and anything else that would draw current and they still dim while in gear.

i'm thinking it might be the 7 pin trailer plug. there is some corrosion in it and it might be shorting out when the brake is applied.

any other things i might would want to check out ??



oh,,, this is happening on my 94

 

[HEYBOSS]

7 pin trailer plug? is it connected to trailer? If not I don't think it would matter. Don't forget that when brakes applied your brakes lights are on and drawing more from batteries.

Sounds like you may have a weak charging system. Did you put on a volt meter on the battery and all loads on see what it reads.



You may have a weak alternator that with loads off is fine, but the minute you start to load up the system it may not keep up.



Good luck,



Fred.





PS. you may want to check all battery and alternator connections too.

 

[AggieJustin]

Is it possible that you were noticing the grid heaters cycling? Now that winter is upon us (well some of us), the grid heaters will be cycling at idle to keep the intake temps up. Whenever they come on, you can see the voltage drop and the lights will dim. Once you get over at set speed (15 mph, I think) they go off and you won't see the dimming anymore.



JM

 

[Cooker]

If they only do it with your foot on the brake I would be inclined to think it is something with the trailer plug as well.

 

[athompson]

Check the alternator.

If it's fine, check the batteries. The only time my voltage meter on the dash dips below 14 volts is when the the grid heaters are on. Then it dips to just over 10 volts. You shouldn't be seeing the voltage drop you're describing. If you had a short in the trailer plug it would blow a fuse.

 

[WestTN]

dim at idle

Have you noticed a drop in your idle speed? It is somewhat common for the P7100 pumps to lose idle rpm's after a while. Possibly you just need your idle speed set up.

 

[Brand-X]

like they said check the charging system and batteries,the alt. can put out good volts and not enough amps . After you find out the charging system and batteries are good and this only happens with your foot on the brake after making sure your idle is good set the parking brake so you can still load the drive line in gear at idle take your foot off from the brake and see if the Gage goes back up this will help isolate the problem if it still does it I would first disconnect the power from the trailer brake controller good luck

 

[**ICEMAN**]

i ruled out grid heaters because it does it even after the truck has been driven an hour or so.

idle speed is fine.

i'll have the alternator checked.

i was assuming it was the 7 pin plug due to an episode with it last year. i would go to leave for work in the morning and my parking lights would be on. switch was off,,had to unplug batteries at work till i finally found that the parking light hot and the ground were connected together with the green/white corrison stuff inside the 7 pin plug. i put a new plug on then but it looks to have that same stuff in it again. i keep it sprayed with wd-40 etc but always seems to collect moisture some-how.

setting here writing this ,,i can remember that the green light(connected) on my brake controller has been flickering now and then(with no trailer etc attached to the plug).

i'll check it out today and post the results after i get my snow plowing done.

 

[**ICEMAN**]

UPDATE "PROBLEM FIXED"

finally got around to fixing my amperage problem.

i had the batteries tested and found that the passenger side battery was dead/toasted.

installed 2 new ones and everything is fine now.

the old ones(2, 1100 CCA INTERSTATE batteries) were close to 6 years old.

 

[JohnG]

If you're spraying WD-40 in the plug and still getting corrosion, it's more evidence (that I've heard before), that WD-40 actually attracts moisture! I would use some di-electric grease or

LPS-3. . JohnG