Hi Boys and Girls,

I have a 1999 Bonneville SLE with 182k (about 70k on rebuilt transmission). Naturally aspirated, bone stock. Electronic climate control. I have a couple of problems:

-Weirdest of the problems - when I blow the horn, the blower motor stops but comes back on within a few seconds of releasing the horn. Seeming like a grounding issue, I checked the battery ground, both horn grounds, main ground near starter, both buss bars under carpeting, alternator (recently replaced) and basically wiggled every single wire I could find. Consistently charges ~ 14v. Headlights super bright; blinkers click fast as expected. I'm thinking perhaps a bad horn as I cannot come to any other conclusion.

-Second problem: Transmission lockup just quit. I'm going to buy a brake switch as I had a Grand Am that did the same thing and a new brake switch fixed it. As it is a $10 part, I'll crap shoot this one. Brake lights and cruise control work fine. Looking for suggestions here as well. Wondering if there may be some tie in with the blower motor problem. Might put in a new horn relay as well; another $10 part.

I appreciate any and all feedback on these issues.

It may be a good idea to have it scanned for codes, because I would expect a bad brake switch to throw one on that generation, and present more symptoms.

Thanks rjolly87,

I did scan with my obdII scanner; no codes. I happened to stop at Pep Boys last night and one of the techs is a former GM tech. His suggestion was that I should replace the brake switch (there are two - he directed me to the correct one). He also suggested I check under the dash as there are other grounds under there that can work themselves loose. He felt my grounding problem and TCC problems were probably unrelated and just happened about the same time. He also said that the brake switch performs many functions that are not listed for the switch and there may be a possibility that changing it out may fix the grounding problem as well. So dash diving I will go and will publish my results.

I think he gave you good advice. Fix what you know is wrong and see what problems are left when you are done. A lot of times the brake switch is not defective, it gets loose and slips out of place. You will find out when you get under there.

Good luck.

Unfortunately not good news. I replaced the brake switch I thought was the problem (there are two) and it had no effect on lockup or my grounding problem. I'm going to replace the other brake switch (has a vacuum line) because it is never clear which switch truly effects lockup. When I have more time, I'll rip into the buss bars again. Not a happy camper.

The plot thickens. Last night I replaced the second brake switch as it was cheap and easy enough to do. While I was under the dash I looked for any damaged or disconnected wires that could be ground related. Finding nothing, I took the car for a hopeful ride that the second brake switch controlled the TCC. No changes, no lockup. I also noticed that there is a "TCC" 10 amp fuse in the left fuse box so I checked that and it was fine.

Getting back to the horn issue, as mentioned previously when I blow the horn, the blower cuts out and then comes back on after a few seconds. I now notice that blowing the horn also turns off the traction control and disables the ABS (according to my dash warning lights). Shut the car off, don't touch the horn and the ABS and traction control warning lights are off indicating normal function. So my circumstances presently involve the horn, blower motor, ABS, traction control and TCC lockup. Obviously a ground issue; I have disconnected the battery several times to reset the ECU/PCM but does not make a difference. I still need to tear apart the passenger buss bar but I'm losing any shred of optimism that I had. Hopefully someone out there can direct me to some commonality of these problems. The only good thing - car runs great otherwise!