I am sure this is an electrical connectivity issue on my 1992 ROW Auto, I could use some help from trusted minds to help figure this out.

Observed Problem: The headlight H4 bulbs will cut out (turn off) under situations where I am doing an extended hard acceleration (WOT but not kickdown), and then return on again after I ease off the throttle (less than 2/3 throttle). It seems to only do this in the higher rev range (above 3500rpm).

• I can recreate the issue pretty easily in 1st, and 2nd gear on a straight road, but will also happen in 3rd.
• The issue is limited to BOTH headlight bulbs and nothing else. The pods stay up. Since the lights are fused and grounded separately, I conclude the the left/right fused circuits are not the issue and the problem is coming from upstream (eg the relay or before).
• The parking lights and fog lights stay active.
• The volt gauge stays constant so I can conclude power to the CE panel is not being disrupted.
• The headlight relay (928-618-017-64) is new in 2021.
• I have verified if the problem persists with the high beams
• The lights do not cut out going over bumps only in these hard acceleration situations

The lights do not flicker when they turn on or off, so my hypothesis is that the relay that controls this circuit within the headlamp relay is loosing power or ground. Does that seem reasonable?

I would appreciate any thoughts on how to narrow down and test for the problem. I have had my CE panel out a few times for cleaning etc, so it is plausible this is a self inflicted issue

 

Here is my best attempt to understand the pinouts and relays in the headlamp combination relay. The low beams are handled by the yellow and blue circuits. The K controller decides to energize the relay with the blue line through it.

As consider the headlights cutting out, it could be:

1. the power from the X bus at terminal 30 (and/or terminal X). However, I haven't noticed other X-bus accessories turning off. it would seem isolated to the low beam circuit.
2. the controller within the relay

In looking at the diagram, I cannot see other faults only impacting the the low beams without also impacting the pod position. Thoughts?

1. 

 

Michael,
check the CE panel is correctly and securely mounted.
I had an intermittent headlight cutout a few years ago which I eventually tracked down to the top of the headlight relay coming into contact with the CE panel cover and turning off the main beams only.

Myles

 

What is the output of the alternator at idle vs. WOT or higher RPM? The diagram shows a transistor in the module for the low beam. I would start with changing that module with a known good one. Sorry. I have more questions than answers.

 

With the car parked and the headlights on can you recreate the problem by pushing on the headlights from the front?

 

Thanks for tips and suggestions. I was able to replicate the issue by rocking the headlight rely back and forth. So I removed the relay and gave everything a dose of DeOxit 100 and made sure I pushed the relay in securely. Hopefully this is the end of this drama.

 

Hi Michael,
I have dealt with the same issue on my '89 S4 5 speed. Every time I thought I had it solved it would cut out but now at a higher rpm. The headlights (low & high beams) both go out at above 4K rpm and originally would come back on after keeping the revs down but now the headlights stay out and come back on whenever they feel like it. Did change to a brand new relay originally with no change. The only time the problem went away is when I ran LEDs for a short period of time. They turned out to have their own set of problems and removed them. Every time I think I have solved the problem it comes back.
Any new tips appreciated.
Mike

 

Hi Mike, thanks for sharing. It's interesting to hear you are having the same problem. I noticed that relay has some play even with it pushed in properly. If the problem persists, I think the next step will be to try to tighten up the grip of the receiving sockets using a pick or small flat blade screwdriver or other appropriate instrument.

Based on the diagram above, I figure there are 3 supply side pins that could influence the bulbs going out:
30 --> Block I, Pin 4
X --> Block 1, Pin 3
30a --> Block II, Pin 8





See if you can improve the contact on these pins, and check to see if your problem goes away.

 

I’m going to put that new relay back in and clean and “tighten” up and Deoxit the terminals and see what happens. Hopefully I will get some results.

 

I replicated the head lights last night pulling into the garage. Brand new relay. Head lights coming and going on the 35 mile trip home at 3-4K rpm. They went out when I pulled into the garage. Stayed out long enough to wiggle the headlight relay. They came back on and stayed on. Even though I Deoxited the socket, the contacts must me loose enough to fail. The relay I thought was rather hot to the touch. Is this an indication of bad continuity in the socket? It seems I may have to remove the CE panel and work from the rear to tighten the contacts. Any other way from the front?

 

Bugger, I am sorry for your situation sounds like you have a clue of where to look next. If you wanted to be sure, you could put some foam above and below the relay to prevent it from rocking (maybe use some tape to help secure it) and retest to verify if the movement is causing the issue.

On my end, I have seems to have solved my problem after one round of testing.

 

I think you should evaluate performance without the relay to be sure it is the issue. Raise the pods - turn the ignition off to keep the pods up - then *remove the relay and connect a switched (and fused) jumper between X and 56b on the socket then drive it an see if you see any issues

*battery disconnected

I'd suspect the relay contact could just be just dropping out under acceleration - could be weak drive to it or the contact spring too tight. Difficult to fix but it would have to be the beam on/off relay. Alternatively: while the beam control relays do not affect the pod drive relays - the pod drive relays do affect the beam relay - beam only comes on when the pods are fully up. So its possible the pods move under acceleration and affect the limit switch in the motor - that feeds back to the relay to control the beam. Adjust the up-stops on the headlight pods a little higher (or lower) - you'd have to adjust the aim again after this. You can maybe test the hypothesis perhaps by wiggling the pods back & forward with headlights on. Doesn't explain the effect of wiggling the relay of course.

Alan

 

Alan,
Last night when the headlights went off when I entered the garage, the first thing I did was strongly shake the pods while they were up. No effect. I can rule that out of the scenario?

I will next jumper the relay as you describe and report back.

 

Not definitive, but less likely - sounds most likely the relay area. Might be worth taking a good look at the terminals in the relay socket - make sure they are all properly in place and haven't been pushed out of place or damaged. its difficult to do anything but evaluate condition from the front.

Alan

 

Bump