buccicone

My 1989 S4 5speed Low beams last night cut out/turn off when I reach 3500 rpm-higher. Most of the time they will come back on with reduction of RPM's below 3500 but not 100%. The high beams still operate and does the fog lights saving me from utter blindness in the dark. The brand new head light relay (latest superseded version) is maybe a year old. Before I spend $180 or look for my receipt any quick answers? My '90 GT I will switch out the relay when I get some time.

gazfish

Are you saying you rev the car stationary and they go out with higher revs or the car has to be moving, could it be wind resistance shifting them slightly causing it?
And usual suggestion of cleaning the grounds if you havnt already.

buccicone

Revving in the garage stationery or moving. Grounds clean but will check again.

MALinPA

No knowledge of this problem per se, but this sounds awfully a lot like an alternator/voltage regulator issue. Although that wouldn't really explain why the fog lights & high beam are not having this issue.
Have you checked to see what happens with the voltage while increasing engine rpm? (And if anything changes at 3500rpm?)

buccicone

Update: Headlight relay replaced with new (the old one was less than a year old). Still failure of the low beams only at 3500-4000 rpm stationary or driving down the road. I've gone over all grounds in the last year. The CE panel was removed and cleaned in the last year. Seems like something is vibrating loose on connections but you would think driving on a rough road would do the same.

Headlight switch?? Ignition Switch??

The Forgotten On

^^ If your key comes out fairly warm you need a new ignition switch. Especially if it is original, they can cause all kinds of weird issues.

buccicone

Another “weird” thing is the window winder relay is very warm when no windows or sun roof is being operated. I don’t think it’s related. Why would the relay be so hot to the touch (had to pull my finger off because of temperature). Will check the temperature at the key.

buccicone

Tested today cold. Didn't like to run up the rpm when cold, but lights stay on. It's a heat issue and time running that's a little more evidence. Possibly ignition switch? I will need to run it a while to get it hot and see if the key is warm. Currently doing timing belt/WP on the GT.

928NOOBIE

I had same thing happen...when too much current is running through that relay (you run both windows at once for example) the relay contacts can get too hot and will get stuck together and can't come apart so that even if you aren't pushing window/sunroof the relay is still on...it will impact your charging as well.....I found the same way...relay very hot to touch...replaced it and no more problems. Run the windows up/down one at a time and run sunroof by itself.

If you have any kind of special relay system to give your car one push up/down for windows make sure the outboard relay is releasing when the window reaches full up or down....I have the system and have had issues with the instant up/down outboard relay releasing and I think that's what zinged my relay....anywho replacing the relay will fix it.

buccicone

Thanks Noobie, this seems like a good smoking gun to start with. Will remove window winder relay and test lights. There is no reason for that relay to be active and hot when windows are not operated.

Mrmerlin

the window relay will run when the door is open or the pin switch is grounded
best thing to do is roll down the windows and verify the door edge lamps are off.
make sure they are working first.
look into the doors and you can see the lights if they are on

buccicone

Stan, that explains the window winder relay. I always was testing for the headlight low beam quitting at 3500 rpm+ with the passenger door open. I’m leaning toward the ignition switch. I have yet to test to see if the the key is hot after running for a few miles. The headlights stay on when tested while cold. Will continue to report back.
Missed you at Frenzy!

Mrmerlin

NOTE best to disconnect the battery if the doors are going to be open for more than a few minutes,
as relays will be energized and after a while they will get hot and can be damaged

I would replace the window relay and the X bus relay,
check the battery terminals, replace the ground strap if original.
also clean the hot post terminals under the hood,
and do a CE panel service with Deoxit 100 on all the fuses and relays,
and the hot wires and the ground wires at the top of the CE panel

jbrob007

Looks like you need a new relay and a call to our favorite Texas-Brit is in order. He may give you a discount since the relay is only a year old. The replacement relays quality are questionable… at best.

buccicone

Stan, as usual you got the answer. I replaced the ”X” relay and cleaned the battery positive terminals. The negative cable was new when I first got the car. Tested this afternoon. Lights are working perfectly. Can’t tell if it was the relay or the little bit of corrosion on the battery. My suspicion it was the relay. The 53 relay looked original. Thanks to Stan and all for your insight.