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Discussion Starter · #1 ·
OK, guys, need some help. Here is what has happened. I have a 08, this morning I went to car wash and washed engine VERY well. Dryed car and left and went to Golf Course. Car drove fine no problems at all. I was at Golf Course about 20 minutes and cart boys came and got me and said my alarm was going off?? I went out and the alarm was NOT going off, BUT the horns were stuck? open. I hit panic button and horn went to sounding like was alarm, but when I would shut if off, the horns kept blowing. I got in and stated are and taped horn button and hit panic button , but no help. I did notice that it sounded like by this time only one horn was blowing...THEN it finally quit....I went on and played golf and came back out about 5 hours later. started car and no problems..on way home, message came on..."Service charging system"....I tried horn and would not work. After I got home, I checked fuse box and horn fuse was blown. I replaced fuse, but horns would not blow. I pushed horn button and one of the horns just "beeped" one time and nothing. Fuse is still good. I then jacked up car, unpluged one of the horns, pushed panic button...I could hear replay clicking (working) AND was getting 12 volts to plug...on ,off, on, off, but horns not working....Do you guys think with the horns just blowing for maybe 10 minutes, they blew their selves out???? ALSO, why do you guys think I would get a message saying "Service Charging System"???.....I AM NOT TAKING TO DEALER, even thou, I have under 36,000....if major problem, yes, but with this NO!!! I have visions of some guy, that knows about what I know, driving around.."checking out" and driving the crap out of it, THEN, them telling me that I have a stero system and I messed up wiring, (system in car is a pro in stalled $8,000 system and has been in for 20,000 miles) and blew out horns, and it is going to cost..$618.32,,haha...SO WHAT do your guys think?
Jim
(Remember NEVER too much horsepower)
 

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OK, guys, need some help. Here is what has happened. I have a 08, this morning I went to car wash and washed engine VERY well. ALSO, why do you guys think I would get a message saying "Service Charging System"
Apparently you got some electrical connections wet and shorted out to blow the horn fuse, which could possibly explain the Service Charging System message. Don't know why the horns would blow out. You would think that they would last longer than that.
 

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That's a tough one. I have heard of strange electrical things happening when someone washes their engine - even if carefully done (which is why I never spray water under the hood). When the car is started and driven after washing the engine it can create steam that can get into places and create havoc.
 

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I suspect the horns may be shot. They are not designed to operate for long periods of time. They probably overheated and blew the fuse. I would un hook the horns and hot wire them one at a time. If they don't work you have found the problem. If they work you have another problem.
 

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Discussion Starter · #5 ·
Wellllll.....here is more now!! I started this morning working on car. First, checked horns and they were gone....so went and bought 2 new horns, almost same horns, only thing that I had to change were conections, but bolted up perfect. They were working fine, and then just quit...opened fuse box and "wiggled" relay (not fuse) and they went to working. Drove maybe 50 miles and they stopped wroking AND same message came on.."Service Charging System"...Came home, opened fuse box and wiggled relay and horns went to working. I then used compressed air to blow out fuse box..REAL GOOD...also pulled out relay and sprayed in a little WD40 and sprayed it out very good. Pulled off top section of fuse box and blew it out. Then switched relays with another same number "bent" prongs just a little and plugged in and made sure was tight. Checked all other relays and made sure they were tight..started car and let run for about 2 or 3 minutes and no message...keeping my fingers crosssed.....OK HERE IS MY QUESTION...Do you guys think that the computer senses when the relay came unplug...I tried to hong horn 2 or 3 times....IF SO that is why message is coming on??? what do yall think???
OH!!! by the way, if any of you guys ever need to replace horns (hope not)...pull off front right wheel, take off enter fender well, air scoupe is part of it and you can get to horns very easy....you do NOT have to pull off whole front end......hope this helps somone.
Jim
 

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We have some sharp electrical guys here that may jump in but here are my thoughts.

I don't think the Service Charging System message can be triggered by a loose or bad relay. However these cars are very sensitive to a weak battery which can result in all sorts of electrical gremlins. Besides just a defective battery if your car has not been driven regularly or if it has been repeatedly discharged the battery life will be shortened. I don't know about the C6s but many C5s had to have batterys replaced under warranty. My 02 battery went out just before the 3 years were up and the electrical system was acting really wierd until the battery was replaced. I used a Battery Minder after the battery was replaced and it was still going strong after 4 years when I sold it.

My guess it that your horn issue was due to water and the battery may be a seprate issue. Have some one give the battery a thourough test including a load test.
 

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Here is what I'm thinking happened. Horns shorted, drew excessive current which in turn burnt the relay contacts and blew the fuse. You replaced the fuse and the horn was intermittent.

If your relay contacts are burned bad enough, it will cause enough of a voltage drop across the contacts to prevent your horn from operating. When you swapped the relay, you eliminated that problem. The PCM might have seen the voltage drop due to the excessive current draw and figured you had a charging problem.

Now all you need to do is replace the relay that you swapped and you should be good to go.
 

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Discussion Starter · #8 ·
Update.....Everything seems to be working fine now....I cleaned the fuse box (under hood)...VERY good, by pulling every relay and shooting a very small amount of WD40 and then using compress air to blow out. I did end up switching horn relay with another relay...bent prongs just a little and made sure it plug in tight...as yall know I replaced horns...BEST ADVICE!!! now I know, NEVER!!! wash motor , clean by hand...yea, know I know. Little advie also, if you ever need to replace horns, it is maybe a 1 hour job, just remove right front wheel, remove enter finder well, and you can get to horns very easy. Also, go to quality auto store and you can buy horns that are almost exact replacement for about 1/3 price...thanks to all who checked in and gave me some ideas.....
REMEMBER , never too much horsepower!!!!
Jim
 

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now I know, NEVER!!! wash motor , clean by hand...yea, know I know. Little advie also, if you ever need to replace horns, it is maybe a 1 hour job, just remove right front wheel, remove enter finder well, and you can get to horns very easy. Also, go to quality auto store and you can buy horns that are almost exact replacement for about 1/3 price...thanks to all who checked in and gave me some ideas.....
REMEMBER , never too much horsepower!!!!
Jim
We all learn from our mistakes, some harder than others. Thanks for the tip on replacing the horns. :yeadog::yeadog:
 

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Discussion Starter · #10 ·
MORE...update...threw same message today..."Service Charging System"...when this message comes on horns do not work, then in about 1/4 mile they went to working again and message went off. IT IS NOT replay, because as I have posted in pass, I switched OEM relay with another one in fuse box. I have a hard time beliving , in fact I KNOW that when I washed the engine (a week ago) the water is all gone...I am kinda at a lost now, do any of you electrial guru's have any thoughts???? One more thing that a couple of guys brought up, I replaced the battery only about 1,000 miles ago and bought the best....
Jim
 

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Some owners of a 2005-10 Corvette or 2004-09 XLR may comment that the Service Charging System message displays on the DIC. DTC P0621 is stored.
This may be a result of aftermarket spark plugs or an open in circuit number 2540.

1. Check for aftermarket spark plugs. Plugs that are designed with a "pulse" technology may interfere with this circuit and cause the Service Charging System message in the DIC and/or P0621 DTC to store in the ECM.

If aftermarket plugs are installed, replace the plugs with OEM parts.
This is not considered a warranty repair and all cost associated with this repair should be the customer's responsibility.

2. Circuit 2540 is supplied voltage from the horn fuse, position 2 in the UBEC.
Try the horn to see if it works.

If the horn does not work, suspect an open fuse.
This fuse may open if the horn is shorted due to water intrusion.

If the horn is functional, check the integrity of circuit 2540 between the UBEC and the generator.
 

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Just Wonderful!! This just happened to me too. I washed car with engine compartment. Ran engine for 20 minutes to dry everything off. Waxed car. Parked car in garage and put car cover on it and went to work. Wife comes home 3 hours later and calls me in a panic while I am at work to tell me the horns are on and she can't turn off with a remote button. I had to call neighbor to come disconnect negative on battery to stop it (yeah everyone is used to a battery in the trunk). She said the horns had changed tone, so they were probably burning out the last time she hung up on me. Based on this post-string, I guess I will need to pull horn fuse in the morning and try to dry out elect box. But it sounds like a dealer visit to replace horns, horn relay and reset computer based on this post. I had open heart surgery a few months ago, so I am not going to try to deal with it. Go figure that a car designed for a rain environment can't take light cleaning of the engine compartment without shorting out! My respect for GM engineering just dropped 5 notches, and I literally just was telling a coworker, how the build quality of the Corvette is so much better than most of their cars!!
 

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Update: I was not able to mess with the car for several days, due to my extended work hours at the Nuclear power plant for our major modification refueling outage (increase Gross megawatts from 890 Megawatts to 1005 MW).

- When I hooked the battery back up, the horns did not come back on.
- A check of the steering wheel horn button confirmed the horns still functioned on/off, but horns sounded sick. Sounds like 1 is blown and the other is hurt.
- Started the car and no DIC codes were shown.
- Pulled the car into the front driveway and opened the hood & electrical box. It was a warm Florida day with bright sunlight and 40% dry humidity.
- Removed the horn fuse (front of box/car) and found it in good conditon.
- Removed the horn relay (front of box/car) and did not see any evidence of overheating.
- Inspected electrical box and found no evidence of water.
- Removed/inspected high beam relay (adjacent to horn relay) and saw no evidence of water.
- Operated high beams to ensure that they worked and did not remain on.
- Ran 1500W hair dryer on electrical box for 20 minutes, with warm sunlight and engine still running.
- Reinserted horn fuse and horn relay.
- Bought 2 new factory replacement horns and a horn relay.
- Drove car 4 times @ 20+ miles without event.
- Will replace horn relay and horns, once I have a couple of weeks to verify that the body control module does not light off horns again.

Pain in butt for an $80K new car! I have gently (not powerwashed) engine compartments for years. My 1990 & 2010 Maximas were impervious. My 2004 Silverado SS has had no problem. My 1994 Z28M6 and 1996 Impala SS required caution that no water got into the opticrap distributors and sometimes had minor belt squeal until dry. Even my daughters 2003 Ford Focus was fine.
 

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I guess if you never drive a car, then you won't ever need to clean the engine compartment. My daughter has not cleaned her car's engine compartment in 40,000 miles and it looks like it is just seconds away from an engine compartment fire with all of the accumulated grease, dust (lawn clipping dust, sand, bug remnants, ???), etc. I have cleaned many engine compartments since the late 1970's without incident. In fact the only problem I have ever had was with the mid-1990's LT1 engines (Z28 & Impala SS), which had the terrible optispark distributors, which would allow water in, but never let it out; ... and even with the LT1 engines, the problems were NOT with my cleaning the engine compartment, but with an automatic carwash. The big surprise with the LT1 engines was if you drove through an automatic car wash, which cleaned the undercarriage. After one pass in a car wash with my Z28, it was backfiring at higher rpms down the drag strip until I finally said uncle and had to replace the distributor. So imagine my surprise after many Toyotas, Nissans, Chevy's, Pontiacs, an Infinity, and even a Ford; when my $80K-new C6Z06 can't tolerate a gentle (non-high pressure & carefully aimed hose) water washing with a soft bristle hand brush!
 

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Jim, the very same thing just happened to me! I have a 2007 Z06 and have always washed under the hood without any problems on late model cars. I washed the engine compartment, sprayed it out and finished the entire car. I went inside and about an hour later the horn is stuck on and I race to the garage and try hitting all the alarm buttons on the keyfob but that just made it crazier! I started the car and ran it for 2-3 minutes and the horns stopped. Back to my den for a beer and about 20 minutes later the horns started up again but this time, instead of one long blaring horn, it now is beeping a horn the way you might say "hello!" or you go first! then it turned into the beeping a really pissed off driver would do! " I store the car at my office when its not home, so thinking I had better get this car out of my neigborhood, and maybe a fast hit drive would dry out the relay panel or whatever it was that got soaked enough to misfire
The 15 minute drive to the office was filled with a lot of puzzled looks from other drivers wonderd what was the problem with the guy in the Vette!
It seemed to beep less......I will wait and see what it is waiting for me when I'm back in the office tomorrow!
OK, guys, need some help. Here is what has happened. I have a 08, this morning I went to car wash and washed engine VERY well. Dryed car and left and went to Golf Course. Car drove fine no problems at all. I was at Golf Course about 20 minutes and cart boys came and got me and said my alarm was going off?? I went out and the alarm was NOT going off, BUT the horns were stuck? open. I hit panic button and horn went to sounding like was alarm, but when I would shut if off, the horns kept blowing. I got in and stated are and taped horn button and hit panic button , but no help. I did notice that it sounded like by this time only one horn was blowing...THEN it finally quit....I went on and played golf and came back out about 5 hours later. started car and no problems..on way home, message came on..."Service charging system"....I tried horn and would not work. After I got home, I checked fuse box and horn fuse was blown. I replaced fuse, but horns would not blow. I pushed horn button and one of the horns just "beeped" one time and nothing. Fuse is still good. I then jacked up car, unpluged one of the horns, pushed panic button...I could hear replay clicking (working) AND was getting 12 volts to plug...on ,off, on, off, but horns not working....Do you guys think with the horns just blowing for maybe 10 minutes, they blew their selves out???? ALSO, why do you guys think I would get a message saying "Service Charging System"???.....I AM NOT TAKING TO DEALER, even thou, I have under 36,000....if major problem, yes, but with this NO!!! I have visions of some guy, that knows about what I know, driving around.."checking out" and driving the crap out of it, THEN, them telling me that I have a stero system and I messed up wiring, (system in car is a pro in stalled $8,000 system and has been in for 20,000 miles) and blew out horns, and it is going to cost..$618.32,,haha...SO WHAT do your guys think?
Jim
(Remember NEVER too much horsepower)
 

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Car horns are not rated for "continuous" duty. In my case, the horns blared for at least 20 minutes straight until I could get a neighbor to disconnect the battery in the trunk. This totally burned out 1 horn and serious hurt the second horn.

After that event, the one remaining horn sometimes worked and sometimes did not. I had bought 2 new AC delco horns (hi & lo) and a horn relay within 5 days of when this happened to me (over a year ago), but only replaced the horns 2 weekends ago; as it is a big pain in the ass to get to the horns.

As both horns blared, it is clear that the water somehow made it to the relay box and shorted out the relay or the circuit downstream of the relay. I ran the car for 20 minutes BEFORE I washed the engine compartment and ran it for 20 minutes AFTER I washed the engine compartment, to make sure that it was ALL dried out. I guess in the Corvette electrical system this is NOT enough. I was gentle with washing the engine compartment, as I have done with all of my cars since the late 1970's. This is the FIRST vehicle to do something like this. My 1994 Camaro Z28 with the optispark distributor, had a problem ONLY if you drove through an automated car wash with high pressure spray coming from underneath the car, which allowed water to get into the distributor, but I have NEVER had a problem like the horns on this Vette.

So I identified the horn relay in the relay box with Blue tape around the relay, so I can quickly isolate the circuit IF it is the relay and have also identified the horn fuse for isolation.

Note that the AC Delco horns that GM provides to replace the Corvette horns are NOT exact relacements. The connectors are different, such that each horn is designed to each connect to a vehicle connector. However, my C6Z only uses a single vehicle connector and the second horn ties in via a piggyback connector on the horns. This piggyback connector on the original horns DOES NOT fit the new replacement horns, and you cannot even connect just a single horn as the connector type is different. I spent 1 hour with the parts guy looking it up on the AC Delco site by both vehicle type and VIN number. You will need to cut off the old connector and splice it in a Y fashion with the new horn wiring. I recommend that you use plenty of heat shrink tubing to avoid creating another short or corrosion open circuit connection point. I had to remove the inner fender well and much of the underbody panels in order to reach the horns. Although you can see the horns from above, you cannot reach the horn mounting nuts or connectors from above.

So if you burned the horns out, you will need to replace them and possibly the horn relay too for good measure. It will set up back about $130 or so.
 

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Note that the AC Delco horns that GM provides to replace the Corvette horns are NOT exact relacements. The connectors are different, such that each horn is designed to each connect to a vehicle connector. However, my C6Z only uses a single vehicle connector and the second horn ties in via a piggyback connector on the horns. This piggyback connector on the original horns DOES NOT fit the new replacement horns, and you cannot even connect just a single horn as the connector type is different. I spent 1 hour with the parts guy looking it up on the AC Delco site by both vehicle type and VIN number. You will need to cut off the old connector and splice it in a Y fashion with the new horn wiring. I recommend that you use plenty of heat shrink tubing to avoid creating another short or corrosion open circuit connection point. I had to remove the inner fender well and much of the underbody panels in order to reach the horns. Although you can see the horns from above, you cannot reach the horn mounting nuts or connectors from above.

So if you burned the horns out, you will need to replace them and possibly the horn relay too for good measure. It will set up back about $130 or so.[/QUOTE]

A separate pigtail is available, at the Chevy dealer, to accommodate the plug and both horns with the new connectors. I ran into the same problem, as above. One ‘parts guy’ went back and found the pigtail that would plug right in to the harness and both horns. Just checked to see if I still had the wrapper, with the part number for the pigtail, but I had discarded it. Apparently, it takes a sharp parts person to know about this. Good luck.
 

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If searching the internet
OE replacement for a pair (high and low tones) is about $13 each
Such as Wolo Manufacturing
 

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Ok, so this is an older posting I found but others are even older and my problem was similar to jmdutko's description after driving through some puddles after an all day rain ~2yr ago. I guess I have just been avoiding big puddles and so far no repeats.

Has anyone determined what the intermittent (or longer) horn problem is exactly when caused by water intrusion? I can't see it being water in the horns; if they short out they would just quit working and not beep at all. Must be water in the relay or the circuit from the horn button leading up to the horn relay. My initial hunch was the alarm system (a bad sensor) but the alarm is a distinct pattern and not a short or long beep.

I thought this was just a one-off on my car and hadn't searched around for a similar problem. I happened on this topic again today as it's been raining all day; I'm staying dry. :)

Thanks
 
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