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buzzing relay

5K views 35 replies 1 participant last post by  xxxxxxxxxxbrodave872 
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#1 ·
Hope this is in the right place.

99 Deville

Loud buzzing coming from up front. Then my hi beams won't stay on. They come on when I pull the dimmer but won't stay on. I did get this code PZ2472 which should be a B code so: B2472 Low Beam Fault.

Found the relays near the fuse box. Pulled the Hi/Lo beam relay. Buzzing stopped. Replaced that relay. Still buzzes. Pulled the headlamp relay. Buzzing stops. Replaced that relay with a new one. This time the buzzing stops but my lights don't work.

Again that is... with the old headlamp relay lights work relay (or something very close to it) buzzes loudly. New relay. No lights or buzz.

Puzzled here.
 
#2 ·
One headlight relay is four pin and the othe is five pin relay. Do believe four pin is main light relay and other is hi lo.
I would check the fuse box connections for corrosion while you are there.
I'd take a shot and say the replacement relay may not be good.
I used horn relay when my headlight relay sent out at night a while back. Since your horn relay should be good provided your horn works headlights the should work then.
 
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#4 ·
So this is weird. The horn relay is the same as the headlamp relay, and it's working so I know it's good.

HL relay in- lights work but relay (or something) buzzes loudly.
Horn relay in- no buzzing, but no lights. And I know that relay is good because I plug it back in to the horn spot and it works.

Thoughts?
 
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#5 ·
I did this again to confirm what happened earlier. I put in the HL relay, the original, and the headlights come on but that relay buzzes like crazy?

I put in the another working relay, say the horn relay... No buzz but no lights either.

Stumped! Any one who knows more boy out by automotive electrical than me have any suggestions?

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Tried a couple more things. Tried the other relays there (DRL, Horn, and whatever the other one was) swapping them all around. None of these would turn the lights on when put in the HL relay spot. Only the old HL relay runs the lights but only with that horrendous buzz.

HOWEVER, that same relay works the in the other positions.

What the heck is going on here?!?!?!?
 
#8 ·
That is way up the old weird stuff o meter... since it stops it must be related to HI/LO somehow. I would jump past the HI/LO relay on either hi or lo and see if lights work and if buzzing stops. If your stalk on column is stuck or bad it could be sending both hi and lo signals at same time and that will freak relays out.
 
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#9 ·
Ok so here's my latest accumulation of information and my latest theory.

The hi beams will flash when you pull the stalk on the steering column but will not stay on. I remembered that this started right before I noticed the buzzing. At some point I remember smelling the "electrical" smell and seeing a slight wisp of smoke over the dash. Very small. Also the same time I noticed the hi beams wouldn't stay on.

The DRLs will come on as normal but not without that original relay in place. The one that buzzes. No other good relays will bring the lights on, and that relay does work at least in the horn spot.

All that together and I have a wacko theory. Tell me what you think.

With the hi beams coming on when you flash but not staying on, the dimmer switch has to be bad. the one under dash on the steering column. First, is that correct?

Second, if that original relay is somehow stuck in an "on" or "partially on" position and the dimmer switch is bad, somehow throwing both hi and lo signals, then perhaps this is the reason why only that relay will work. And when I change the dimmer switch and put in a good relay, that should fixe the problem.

Does my theory make bizarro kind of sense? Is there anything else I should check or consider?

Everyone always says trace and check grounds, but I can't imagine a ground causing something like this.

OK, gentlemen. tell me what you think.
 
#10 ·
I would unhook the turn signal wiring, but me thinks you may have found the issue. Don't have a good answer why the original relay works other than it is worn and confusing the diagnostics.
That's why I said the jump the relay wiring to low and high independently and see if both work and if buzzing stops.
The DRL have their own wiring I checked. they should work independently from low beams if I'm reading the diagrams correctly. The DRL should only be coming on if car in gear not park also(don't know how you checked them).
I will walk out in a bit and take my HL relays out and check DRL operation. and post back know good.
 
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#11 ·
The DRLs do disable when the HL relay I pulled.

Walk me thru jumping the relay hi and lo. Haven't done much electrical work myself in a long time. Don't want to burn something up.

Is that on the hi-lo relay? Which contacts?

Can you give me a step by step? If at this point you think it's still helpful or should I just go ahead and replace the dimmer switch?
 
#12 ·
well I just checked and DRL do not go off if you pull the relays for either headlight or hi/lo.
That would be a problem then.
The PZm sends signal to DRL relay when car in gear and HL not on by switch or twilight sensor.
DRL wiring is completely separate until headlights themselves. From fuse panel to relay to DRL resistor(behind battery) and to the headlights themselves.
If the HL ground(s) are bad it could be back feeding a ground.
Usually a buzzing or clicking relay is a short somewhere.

I walked out and jumped and here is what works.
ON HI/LO relay:
Find the numbers on bottom of relay and jump the terminals in fuse panel:
30 to 87A for Low
30 to 87 for High
If cant read google 5 pin relay (siemens 12135180)
30 is bottom row of 2 towards the engine. 87A is top center and 87 is top towards FENDER.
double check before you do it please.
 
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#13 ·
rodnok01 said:
well I just checked and DRL do not go off if you pull the relays for either headlight or hi/lo. That would be a problem then. The PZm sends signal to DRL relay when car in gear and HL not on by switch or twilight sensor. DRL wiring is completely separate until headlights themselves. From fuse panel to relay to DRL resistor(behind battery) and to the headlights themselves. If the HL ground(s) are bad it could be back feeding a ground. Usually a buzzing or clicking relay is a short somewhere. I walked out and jumped and here is what works. ON HI/LO relay: Find the numbers on bottom of relay and jump the terminals in fuse panel: 30 to 87A for Low 30 to 87 for High If cant read google 5 pin relay (siemens 12135180) 30 is bottom row of 2 towards the engine. 87A is top center and 87 is top towards FENDER. double check before you do it please.
Hmm... I could have sworn my DRLs went off when I pulled the HL relay, but with the other weirdness that could be another symptom.

On the jump, I'll look at it tomorrow. Just use a short wire and touch to those two contact points?
 
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#15 ·
OK here we go. Jumped the relay with the dimmer switch under dash both plugged and unplugged. Both times the lights work as they should (hi & lo) but still buzzing. Tried jumping with another relay for HL. Nothing.

Also, I turned the key on forcing the DLs on. They do not burn when I pull the HL relay. I'm wondering if that's just a difference between my 96 and your 98. There were a few differences.

I haven't bought a switch yet, since that now might not actually be the problem.

Any ideas what to try next?
 
#16 ·
Do it again with the DRL relay unplugged. There just may be different wiring for the DRL between years, I do not have specific 96 diagrams. I would even start unplugging the headlight wiring harnesses and see what happens. Should be able to see under the lights with hood up. The idea would to isolate the fuse panel into the car. If it stops buzzing the problem should be from panel to lights(or DRL even). I still think something is back feeding through the lights not sure what.
Makes zero sense they only work with the old relay.
Does the HL relay work in horn spot?
These years are know to have rotted fuse panels underneath and cause all kinds of problems also.
Elec problems can suck and it's probably a minor issue of course it's in a hay stack...
 
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#17 ·
rodnok01 said:
Do it again with the DRL relay unplugged. There just may be different wiring for the DRL between years, I do not have specific 96 diagrams. I would even start unplugging the headlight wiring harnesses and see what happens. Should be able to see under the lights with hood up. The idea would to isolate the fuse panel into the car. If it stops buzzing the problem should be from panel to lights(or DRL even). I still think something is back feeding through the lights not sure what. Makes zero sense they only work with the old relay. Does the HL relay work in horn spot? These years are know to have rotted fuse panels underneath and cause all kinds of problems also. Elec problems can suck and it's probably a minor issue of course it's in a hay stack...
Jumps still work with DL relay pulled. Working now on getting. The relay panel pulled out to inspect. Gonna trace and inspect.

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Checking Inadvert relay next to relay panel, fuses, and the connections at the bulbs. The buzzing stops if I unplugged both lo beams. I guess there's nowhere for the power to go, but it's still there. Plug on back in, buzzing returns. Didn't think to jump the hi beam relay without the hi beam bulbs plugged in.

Try that? Does this tell us anything?
 
#18 ·
the ground for all the headlights is from FSM:
On the left front corner of the engine compartment, on the radiator support

I would check and clean that and start looking at headlight wiring I guess.
If everything was fine the relay should act the same regardless of the headlights being plugged in.

You can test for power at the Hi/Lo relay using OLD and a different relay to see if any difference. if power using both it's just luck(bad or good) that they works using old relay. Terminal is 30 to test for power coming from HL relay.
 
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#19 ·
If I was able to jump the relay, doesn't that show it's got power?

Is the ground on the battery side connected with the big wire from the battery? Not sure which one. Can you show with a pic?

What's FSM? I know I'll probably have a duh moment when you say.

By the way, you're being tremendously helpful. Thanks much!!!
 
#20 ·
FSM= Factory Service Manual check ebay they run 30-60 for a set usually. INVALUABLE especially when stupid stuff goes wrong.

G101 shows up on drivers side under the corner brace with 2 grounds going to it, looks to be tucked up there good.I checked my 98 and there are 3 grounds on rad support and I would clean them all.
1 is near battery
1 is Drivers side off to side of rad and easily seen(wire goes down and out of site)
1 is behind the wire loom(has two lugs that wires go into harness covering the ground)) and very hard to see, you'll prob have to take corner brace off at least. It is drivers side also about half way between rad and fender.
That last one shows as G101 in FSm, but who knows for sure if HL are using this one, things change and FSM is wrong sometimes.

FYI these are very picky about grounds .

Also the DRL has a connection right there near the batt ground on my 98(I know they are wired differently over the years).
I would check for continuity from the ground lug to the lights.
 
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#21 ·
FSMs on eBay I see Haynes and Chilton, which I know. I see the GM ones, I think. Green looking cover. Say E/K platform on the front, very expensive.

Them there's one in two big binders. Like 3 inch binders. That ones $40. Only see one. That the one I need? I searched "repair manual cadillac 1996".
 
#22 ·
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#23 ·
Could only find two of these grounds you're describing. Next to battery and driver side between radiator & fender. Tucker under in front of the air box but easily seen. Can't find another.

Cleaned those two and it got weirder. Not lights inside or outside. The inadvert relay was clicking loudly. Weird part was when I turned the headlight switch back off it stopped and a click came from somewhere else I couldn't pinpoint. Going to replace that relay and see what happens. Have read a lot about those things acting weird.

Any ideas about the third ground? The wire loom is the big panel the fuses and everything is on?
 
#24 ·
In case I didn't mention it UNHOOK the battery when messing with grounds or weird stuff happens also.
I unhooked one for the BCM without unhooking battery ground and man all kinds of stuff started clicking when I hooked it back up until I unhooked battery.

May or may not be 3 grounds on your car, they only show 2 for mine IIRC anyways. Did the drivers side ground have more than 1 wire going to it?
I didn't pull airbox out to check where those drivers side grounds go, they may be another near the fuse panel even for it. There are so many grounds makes my head hurt trying to find them... The FSM lists no less than 6 under the hood for a 98.
 
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#25 ·
Well on Saturday I found and clean the two grounds on either side of the radiator. Couldn't find the others at that time. Didn't see your post unit after I gave up and dropped it off at my mechanic's place. Went by today and we're both still puzzled. HOWEVER, it's at least related to grounds. He temp grounded that relay and it stopped buzzing consistently. We might just add a ground there, but I'm having him continue because I'd rather find out this real issue incase it causes anything else weird.

I aldo replaced the dimmer switch by the way, and no improvement.
 
#26 ·
I'd have to look at FSM to tell you where the ground is for the relay/fuse panel. I mentioned grounds are used to control a lot of on/off on these. It could possibly be something unrelated(ground) causing your issues.
Besides the grounds you cleaned there is main engine ground, ground on trans(weird connector), ICM ground, think ground on water pump area. I'm sure I'm forgetting one or two. Inside the car, both kick panels(two on right side probably), behind/under back seat(1 on x brace, 2 under seat bottom front edge), probably seat grounds(frt), trunk has 2 or 3 at least. Thats just the one's I can remember off top of head that I have actually seen.
 
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