QuestionQUESTION: I have a 1970 Deville Convertible whose battery continually drains, I think it may be the horn relay as the horn no longer works, could you tell me where the relay is located for this particular model? Thanks- Garrett
ANSWER: Very likely, you have two independent problems, because horn failure is in the steering wheel circuit, about 99% of the time. But, to answer your question, the horn relay is a black, rectangular box with 3 wires on it, mounted to the metal panel that is behind the left headlights, under the hood, behind the radiator. To check it, short from the "B" terminal to the "H" terminal - that should make the horns blow. If it does, then short the "S" terminal to the "-" terminal of the battery - that should also make the horns blow, and if it does, the problem is in your horn circuit between the relay and the steering wheel switch. All that switch does is ground the "S" terminal of the relay, but to service it you have to take the steering wheel apart, and may have to remove the steering wheel to get at the problem. You can check the connector from the steering column harness to make sure it is plugged in solidly first - sometimes those work themselves loose. Also, of course, check the horn fuse! With that old a car, typically, if the car has been east of the dry southwest most of it's life, the fuse clips will be corroded, so while the fuse might be OK, it might not be making good contact with the clips. You can use a test light to see if there is 12 volts on both ends of the fuse AND on the clips that hold the fuse (there should be).
If doing the first test at the relay does makes the horns blow, but the second test does NOT, the relay is bad, but this has nothing to do with your battery draining.
Now, to the more important problem:
I doubt your battery drain is going to turn out to be a bad horn relay - it would have had to fail in a way that makes it draw current, but not blow the fuse, and not sound the horns - highly unlikely! After you've checked the horn relay, it's time to start the detective work.
I really need to know how quickly the battery goes down, before I can give you a good proceedure to follow to find out what is staying on in the car. Most everything in the car is automatically disconnected when the key is off, so the problem has to be in one of the few circuits that is on WITHOUT the key. Glove box, underhood and Trunk lights come to mind, along with power seats, courtesy lights, power antenna motors are all likely culprits. If you can pull the fuses from all those things and it continues to drain the battery, something is probably wired wrong.
Get back to me with a "follow up" question if you want to get into a process of tracking down the culprit after you check those few things. Tell me if you have or can borrow a VOM (Volt-Ohmmeter) or a test light, and are comfortabke with using them. The VOM needs to have an AMPs scale that goes up to at least 10 amps. And, tell me how many hours it takes for the battery to go down to the point where it will not start the car when you park it after a drive of at least 1/2 hour.
In the meantime, disconnect the "-" battery cable each time you park the car, just to prevent a fire until we get it fixed.
Dick
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QUESTION: Ok so the problem may be a little different than what I thought. Last year I had replaced the battery with a wal-mart battery, in checking the two batteries recently the walmart battery had 600 cold cranking amps, vs. the old batteries 725(600 is the minimum recommended by the factory, but mine has an aftermarket radio and the power convertible top). The ampmeter inside the car registered 20amps with the old walmart battery, which im told is a sign of a defective battery ( 20 amps even after the car was running for 5 minutes with no extra load on the system). I just bought a duralast with 825 CCA's and turned the car on, ampmeter read under 10amps. I have since disconnected the battery awaiting further response. My Deville has no glovebox light, underhood light, trunk light or power antenna. None of these were put in by the previous owner during the cars frame up restoration for whatever reason. I have also since disconnected the power seat wires underneath the seat as I am the only one who drives the car and the seats are at my liking. Is it possible that my problem was just the defective battery. I have a multimeter and a test light and wanted to know what can be done to see if there is parasitic draw, or if that is neccesary anymore - Garrett
ANSWER: I think we need to do a bit more before you can relax. Can you clarify when you see the reading of 10 amps?
If you are talking about the ammeter reading a DISCHARGE of 10 amps when the engine is off, and nothing is turned on, that's a problem we need to track down (and you should continue to disconnect the battery until we do).
If you are saying that you see a CHARGE of 10 amps with the car running, that is the charging system replenishing whatever was taken out of the battery when you started it, but it does sound a bit high, even if that is what you mean. In either case, I think we need to do some checking.
The easy thing to do is to make sure everything is off, and then connect the test light from the + terminal to the - terminal on the battery (to make sure it is awake and working) and then connect it between the disconnected battery cable end and the post that the cable would be on if it were connected. It doesn't matter which end of the test light is on the cable end and which end is on the battery post, and it doesn't matter which battery post/cable you are disconnecting.
Now: Does the test light come one when you touch it to the two points? If so, there is a current drain still, and your battery will still go down if you don't fix it, and there is still danger of a fire, so let's keep going here.
If the light does not come on when you do the above test- there is no current flowing when everything is off, and you can relax.
I'll wait until you come back to me with what you know so far, and we'll take the next step, if we have to (tracking down the current thief).
Keep your chin up, we'll git it!
Dick
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QUESTION: Ok now that I am a little bit more knowledgable about electrical systems etc. I have some information that will actually be useful. With the car sitting and nothing on the battery has 12.7 volts measured through the multimeter. When the car is on and there are no accesories running the battery registers 14 volts at the terminals. Now comes the not so fun part. When you disconnect the negative battery cable, and attatch the multimeter to the wire and terminal (measuring for current now), the reading is 3.6 Amps, meaning there is a draw somewhere. I then did the same test but this time removed the first fuse from the fuse box, shut the car door, and there was still a draw of 3.6 amps. This process was repeated with each individual fuse and both circuit breakers, the draw was still the same for each one. The reading of 10 amps from the previous question refers to an aftermarket ampmeter inside the car. It runs just a little below 10 amps with the car at idle. Hopefully the information I have given you is a little bit more helpful than the previous questions have been. The car is currently sitting with the negative cable disconnected.
ANSWER: OK, you are now a skilled auto-electrician! You have no idea how long it has taken to get some folks up to your level!
The 3.6 amps drain certainly explains your battery drain problems! That is about the drain of brake lights stuck on, but I'm sure you'd have noticed the red glow. It could also be a cigar lighter stuck in its socket - check the back seat lighters!
You are tracking it down exactly the way I would. I'd now leave every thing disconnected that is already in that state, and then try further disconnections. Next thing I would try is the alternator (I suspect a failed diode). Find the one large wire on the alternator, and with the battery cable off, remove that wire from the alternator, then see if you still see 3.6 amps drain. I'm betting that will now be gone, but if not, we'll have to dig further.
As an aside, if I haven't already said this, it would be a good idea for you to arm yourself with the factory shop manual for this car - it contains the wisdom of the ages regarding the car, and of course has a wiring diagram which shows EVERYTHING. The shop manuals run on eBay frequently, or you can contact one of the auto literature dealers and get one off the shelf. An original is to be preferred as the pictures are much clearer, but a competent reproduction is a close second, and much cheaper. One literature dealer is Ed Faxon, at www.faxonautolit.com
Your mention of a hang on ammeter concerns me - someone has been creative in the electrical system, and no doubt that is going to complicate troubleshooting - we have no idea what may be connected to the wrong place.
But try the alternator - if that isn't it, try any other wire you can find that looks like it was added after the car left the factory - something ain't right, somewhere.
Get back to me with your findings, please. I'm going to appoint you my representative in your area!
Dick
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QUESTION: Dick, hope your vacation went well, I had been busy with work so was not able to immediately further troubleshoot the Cadillac for the draw. I do have good news though, I have isolated the parasitic draw. My car is equiped with a Delco Remy 10s Generator with an internal voltage regulator. This model has two terminals and the "bat" post in the back. When you disconnect the wire going into the second terminal, the car read a draw of .26 amps, instead of the 3.26 amps earlier reported. Is this definite news of a bad diode? If this is the case is it cheaper/easier (in terms of finding parts) to replace the entire generator, or are diodes readily available. Thanks so much for all of your help - Garrett
AnswerYes, we had a nice few days away from this machine - our local old car club had a tour event - since I'm the newsletter editor, it was a command performance!
The diodes are probably available, but they are not usually sold to repair shops, as it takes a special tool to press them into the housing,and some experience disassembling and re-assembling an alternator including soldering wires etc. My advice is to take the alternator to a reputable auto parts place and turn it in for an exchange rebuilt unit. I prefer NAPA stores for this - the el-cheapo places will have much cheaper units, but their idea of a good rebuilder is the lowest bidder. NAPA has cheap units also, but they also have a premium line which is done right. All of them are covered by a free replacement warranty, but you don't want to have to do this again in 6 months!.
The 1/4 amp drain is quite small, and probably won't cause you much problem, unless the car sits for a week or more, but it would bother me to settle for that. That is about the drain of a small light bulb - and it will run the battery down in a week or so. I'd stay on the trail until you find the culprit. Someone has been fiddling with your electrical system, and probably has something that is suppose to go off with the key hooked up to the "always on" 12 volt circuit. If anything works with the key off other than the power seat, cigar lighters, or courtesy lights, I'd investigate that particular item.
Dick
