Hello everyone I hope that some wise guru will be able to answer the follow question, why is my car trying to kill me?! Here's what is happing: as I'm driving along I will hear a "click" sound (sounds like a relay under the dash), the climate control blower slows/stops, the dash lights dim, tail lights dim, and the headlights cut out for a split second.Just as quickly everything goes back to normal. It seems to happen the most under braking but it will (rarely) do it just cruising down the road also. I've had it in the shop twice for this problem. 1st time they replaced the alternator (was dropping from 14.7v to 9.8v). This seemed to cure the problem for a while but about 2 weeks later it was doing it again. This time in the shop they could not make the car act up, at first I was doubtful but it has stopped, for now. Any Ideas what is going on? I like the car but if I cannot get this squared away I will be forced to sell it. Help and Thanks!

 

It would be nice to know if this Sonata has the automatic headllight option. That may help others understand the problem. If so, I know those auto light functions are routed through the body control module (aka, BCM). A bad relay associated with the BCM would explain most of the other symptoms, but I don't know if the blower control is related to the BCM. Perhaps the car has simply become psychotic.

 

Yes it does have the auto headlights. It does'nt matter if the switch is set to auto or not if that helps. I don't why the car hates me, I change the oil on time, have the prescribed service done, etc.

 

The BCM is an integrated circuit board that's mounted inside the relay and fuse box underneath the dash board on the driver's side of the car (which may explain the click you hear). It controls a whole host of functions and has additional relays incorporated onto it. If you browse the various vehicle forums on this site, you will find lots of threads describing weird electrical problems associated with this circuit board. I hope your 60K bumper-to-bumper warrenty is still effect, because I think a Hyundai dealer needs to deal with problem. Question, has the car been jump started in recent history, like just before this problem manifested itself? I'm curious because you mentioned an alternator problem and a lot of the aforementioned threads always seem to start with "I had to jump start my Hyundai and now my electrical whatever isn't working right". Many end up replacing the BCM. My advise isn't much help, perhaps someone with more detailed knowledge will respond. I wish you luck.

 

I have never jump started the car and now I never will. ken99 from what you are describing itsounds like my problem could be the BCM. The car has been to two dealers for this problem. I still have 11000 miles left on my bumper to bumper thankfully. The problem is so bad thatI cannot drive at night for fear that it will start going crazy again and I will be drive a car with lights that flash off every 30 seconds or more in heavy traffic.

 

iwuzwhatiwuz - I'm sorry, I didn't mean to scare you with the jump start comment. There may well be a time when you will need a jump start. I think some, if not all, of the jump start problems may have resulted from the jump start procedure while the key was left in the "on" or "accessory" position in the dead car. When drivers turn the key and nothing happens, they quite often forget to turn the key back to the "off" position before dealing with the issue. IC boards, like the BCM, are notoriously sensitive to electrical surges. If someone has the engine rev'd up on the boosting car when the cables are connected between the batteries with the key on, that shot would be felt through the whole system. The situation could be made worse if the cables are hooked up backwards, if only briefly when the mistake is noticed. This is speculation on my part, but I think if a person remembers to turn the key off before jumping and leaves the key off for the few minutes the dead battery is being recharged by the boosting vehicle, these problems are avoidable or at least minimized.

 

hi all,
this conditioncould be caused by a poor ground contact under the hood. have the tech check the ground terminals for good and clean contact.

 

I had a similar problem with my 2006 Sonata. Intermittent dimming of lights, wiper slowing down, radio cut out, blower fan etc all typically lasting about 2 seconds when I would touch the brake or even just take my foot off the gas. Seemed to be worse in damp winter conditions that in the summer dry heat. First time I had the vehicle back at the dealer they could not reproduce the problem so they refused to deal with it. Second time they found a TSB that supposedly addressed the issue but the fix only lasted for 1 day. The third time they simply replaced the battery negative cable and all has been well now for over a month. Perseverence sometimes pays off!

Dave