Blogs Car Info Our Show Deals Mechanics Files Vehicle Donation

Volvo 740 - Endless Electrical Issue

I’ve been on here before about this. We’ve got a drain and I don’t know wherefrom. Been through (what will be) 4 batteries in 6 months. We replaced the alternator (no change) and I put a kill switch on the battery. Still, it died today after a new battery two months ago.

I’m probably just going to get rid of the thing because I’m fed up with fixing it. Just curious if anyone has any last ditch efforts to save me from a hefty car payment…

Have you had anyone actually check out the systems? What did they find?

Can you explain how you wired in your “kill” switch?

Have you used it religiously?

What are your usage habits with this car (i.e. how often is it driven and for what time/distance)?

I suggest you have a shop that specializes in electrical repairs look into the matter. They will be able to pinpoint where the drain is at. For about the price of the first new car payment, or maybe less, they should be able to find and fix the trouble.

Not really. They’ve checked the connection to the battery and alternator and that such thing, but since it seems to be somewhat of an electrical gremlin, I don’t want them to just have at it and then come back with a bill for hours and hours of labor looking for it.

Didn’t wire it, just put the standard kind right onto the terminal, it’s got a screw knob on the top, you turn it to loosen it so it doesn’t connect, and you turn it to tighten it so it does. We’ve used it religiously, give or take the occasional slip up. The battery still died in the same amount of time it has died every other time, even with the use of the kill switch.

I’m hesitant to take it somewhere for the electrical problem because it could be anywhere. We’ve already dumped over $1500 into fixing this piece of crap and we’ve only owned it since February 2007!! Since the problem could be anywhere, I don’t want them to find it, after hours upon hours of looking, which will be costly for me. Was curious if there is something I’m blatantly overlooking…

If your batteries are dying even with use of the kill switch, perhaps the problem is occurring while the car is running/on? I wonder if something could be damaging the battery while the car is on. Someone with more knowledge of automotive electrical systems can give you a better idea of whether or not this is possible.

You came here with this self-same problem in 12/27/2007. Much of the advice still stands. Since you can’t do the troubleshooting, you really need a shop do it for you. A capable shop should be able to pinpoint the faulty circuit in a couple of hours. You could stipulate to the shop that you’ll only authorize two hours of diagnostics. Doing nothing gets you nowhere.

More of the usual good advice from Hellokit. I totally agree about just limiting the time spent on the problem. If the problem isn’t something that is intermittent then a good tech should be able to pinpoint the trouble circuit within a half hour. When you have the right tools, service data, and trouble shooting knowledge, it makes finding this kind of stuff pretty easy, which is why they should get paid well for what they do. I know there is out there, the other end of the spectrum, which makes you feel they way you do, but there are good shops out there. When you deal with one, you don’t mind paying for the work done. If you don’t know of one close to you, you may be able to find one through the Mechanix Files that is available on this site also.

Replacing the battery 4 times in 6 months points to nothing more than wild guessing. I only remember this problem very vaguely but did you ever inspect the battery cable ends, and more importantly, inspect for any corrosion at a distribution terminal?

With a freshly charged battery, and the negative cable unhooked, simply touch the cable end to the battery negative termnal lightly and note what type of spark you see.
If there is a noticeable blue spark then you have a voltage draw in the system worth worrying about; if the spark is faint and yellow in appearance then that is probably a non-issue (that is likely the clock at work).
That’s strictly a crude, back yard method but it does work.

Believe it or not, the problem with your car is probably going to be comparatively simple to figure out. It’s going to require a simple methodical approach to the problem.
You stated you do not want to pay a shop to repair this, well sometimes you have to bite the bullet. The problem is not the car; it’s a failure to turn the car over to someone who can properly diagnose it and repair it.
An alternator, kill switch, four batteries, and a ton of aggravation would have already repaired it more than likely.

The one thing I’m curious about is if you’re paying for all of these batteries or how in the world someone is covering them under a warranty. ???

OK, that’s the best method of fully isolating the battery. I think it’s not a drain but actually insufficient replenishment by the alternator. The service battery is designed to start the engine, supply energy to certain systems when the car is off, make up for peak demands when operating and act as a capacitor to smooth out the alternator output. The alternator must replenish the charge lost in the battery and supply the working demands of the vehicle while it is operating. If the alternator is not capable of restoring ALL of the battery charge, it will can slowly deteriorate to the point it no longer can start the car. It’s also a spiraling death since low charge results in sulfation which contributes to the demise.

What I believe is happening is that there is a marginal connection between the alternator and the battery or in the sense circuit that determines how much output the alternator should supply to the system. Check every connection, terminal and wire end at the battery and alternator for signs of corrosion. An electrical diagnosis would involve checking not only the terminal voltage at the battery terminals (not the connectors, but right on the terminals) but also the current capability of the system. You can have a situation where the battery terminal voltage is correct but the current is being limited by a bad connection.

Wal-Mart. They don’t keep track of who returns them. So I only paid for the initial battery.

Also, I’ve had it preliminarily looked at, and also consulted my normal Volvo mechanic who said that the only thing they could/would do would be to hook a voltage meter up to it and pull each fuse to see where the draw is, which could be time consuming on their end (not sure how… seems fairly simple). It’s not that I’m cheap per se, it’s that I bought this car from auction, I’ve owned it less than two years and already poured $1500 into it. The electrical problem isn’t the only problem it has, so I’m trying to assess when to cut my losses and just get rid of the thing.

All the connections to and from the battery have been inspected, cleaned, tightened, etc. Also the same with the alternator.

I think you biggest problem is that you keep going to mechanics for this problem. You need to find a specialist in automotive electrical systems. A specialist should be able to locate the problem and repair it for less than one new car payment, certainly less than two.

BTW, is there anything electrical that is not working, like a power window or mirror, that would be the place to start.

I thought of that. Everything electrical is working, except the back wiper, but I think that’s actually a mechanical problem.

Like I said previously, I agree with taking it to a specialist, I just don’t want to dump another few hundred into it just to have something different go wrong next week/month. I know this seems annoying to you all, but in my mind I sort of drew the line and if anything else major (meaning over $200) happened I was getting rid of it. So, trying to feel it out…

This makes the most sense out of anything… however when the alternator was replaced (within the last 8 months) we checked the connections, and they (supposedly) were checked again within the last 5 months. I will go through them again (with assistance to make sure I’m not missing anything) to make sure they’re all clean and tight. Can you think of anything else that is alternator related that could be causing this?

NEW INFO! My husband said there was one night where he went to roll up the back windows (power), and the headlights dimmed when he did it. I mentioned this to the service guys via email and they had this reply:

“If the lights are dimming when rolling up windows, it could mean the alternator is not charging at a proper rate, but may be the voltage regulator’s fault. There are carbon brushes on the regulator that get worn and don’t allow the battery to be charged properly. Regulator is on the alternator.”


Who replaced the alternator? There should be a warranty on it…could’ve been a bad alternator, even if it was new/rebuilt. But that’s just me guessing. I think it can be tested fairly easily and eliminated/identified as the cause.

I’ll have to noodle on it for a bit. In the meantime, you didn’t answer one of my original questions-

What are your usage habits with this car (i.e. how often is it driven and for what time/distance)?

BTW- just looking at the connections will never be definitive. What needs to be done is someone with a digital volt meter and current probe needs to measure these parameters.

I had the alternator tested when the problem continued, and the alternator was said to be fine. My brother in law helped me replace it, we bought it used from a junk yard, so no warranty.

If it WERE to be the regulator… I’m looking them up on Rock Auto… do I have to buy the kind that corresponds with my alternator? I.E. I have a Bosch alternator so I need a Bosch Regulator?