Readers Respond

October 1, 2017 | By Staff

A Reader Recently Complained About the Repeated Alternator Failures In His Volvo With a Ford V-8. Other Readers Responded With Helpful Advice.

Some Insight Regarding Those Repeated Alternator Failures

Editor’s Note: In the March Mechanic on Duty reader Peter Harding said that a previous owner had placed a Ford V-8 with an automatic overdrive transmission in his 1985 Volvo. Harding said the car “runs great but has an electrical problem no one has been able to diagnose.” That problem has been repeated alternator failures. Since Harding’s letter ran we’ve received a number of responses from readers and want to share some of them here.

Hi Ted—It’s been awhile since you have had any odd electrical problems. This is in response to Peter Harding and the Volvo-Ford conversion. For all of those alternators to fail, it sounds like the output wire (B+) is going to ground, or dead short. You are correct in suggesting starting with the battery. It’s easy to take another known good one and install it and eliminate that first.

I have had four- and five-year-old vehicles come in with warning lights on (Check Engine, ABS, etc.) and they won’t even scan, and we have replaced what was a battery that never showed any problems and cured the other problems. Plates in batteries DO short out, but sometimes they will still appear OK. Always have them load tested.

As far as the Volvo goes, the first thing I would do is put on a 1-wire alternator, (any brand that fits) and install a temporary wire direct to battery positive from Alt. B+. A 10-gauge wire should be fine. Too bad he is so far away; I keep loaner alternators around just for these problems.

Doing that should hopefully keep it operational while figuring this out. We don`t know if the original alternator output wire is where they get the main feed for the car or if it is at the starter or a junction block solenoid on an inner fender or the firewall. Hopefully the main feed is from the battery positive at one of those locations and the car will still run. The whole reason for all of this is so that it will stay driveable without eating alternators and everything can start being hooked up one thing at a time with an automatic resetting circuit breaker. I like those because they are affordable, and if one pops on a test drive I haven’t burned anything up and it will reset and go again after cool-down. I know this sounds like the long way around the barn to fix this, but I would bet that it is a pinched wire or the way the alternator was wired. Not knowing what parts were used and how it was wired, it is tricky to figure out.

Feel free to give Peter my e-mail and phone number, and I will try to help him out. By the way, if this is printed I answer all calls and e-mails.

Todd Heidenreich Todd’s Auto Electric Columbia City, Indiana ;

There are several possibilities regarding Mr. Harding’s alternator woes and you did mention many of them. A little more information is needed to truly diagnose it, but here are some suggestions and diagnostic steps to follow.

He mentions that he installed a test meter near the battery and a voltmeter in the dash, but did not say what the readings were. The first test is to put a voltmeter across the battery terminals. He should see charging voltage of 13.5-14.5 volts with the engine running. If not, check for battery voltage (key off) at the alternator output terminal, it should be equal to battery voltage, which should be very near 12.5 volts with the key and all accessories off.

If the battery voltage at the alternator output terminal is not within .1 or .2 volts of actual battery voltage, the problem is in the output wire from the alternator to the battery or a dirty/rusty connection on one or both ends.

The next test is to check the alternator for a good ground. Some alternators are mounted in rubber mounts for vibration and therefore require a separate ground wire. He can test for ground by connecting a test light from the battery positive post to the alternator casing and it should light up indicating a pathway from hot to ground. Also make sure there is a ground wire that connects either the battery or the engine to the chassis. All too often, people leave these off when working on their cars, especially when doing an engine change or other major work. Remember that the engine is mounted to the frame with rubber mounts and the body is mounted to the frame via rubber mounts also. You need a ground wire connected from the battery to the engine block, head etc. for the ignition system, starter and alternator, but you also need a ground wire to ground the body and chassis for things like lights, gauges, electric fuel pumps, etc. The one thing most people do not consider is that current has to travel from the battery positive, through the load (bulb, electric motor, etc.) to ground and then back to battery negative to complete the circuit. Bad grounds are often the culprit and have caused many a mechanic to want to commit themselves to an insane asylum. Many vehicles of old used a braided copper strap from the engine to the firewall, and/or a 4- to 8-gauge copper wire from the battery to the radiator support or inner fender. I recommend doing both. Especially on the ground side, bigger is better.

The other thing he did not mention (but you did) was whether his alternator had an external voltage regulator. But either way, the diagnosis is the same. He needs to check for voltage at the regulator. I am unfamiliar with Volvo wiring, but his wiring diagram should show a wire from the ignition switch to the external regulator or to the plug on the alternator if it has an internal regulator.

Since he mentions the car has been changed to a Ford V-8, they may have used a Ford alternator so he would need to locate an appropriate Ford wiring diagram.

Again, he should see voltage within a couple tenths of actual battery voltage at the regulator input wire (key on). If not, he needs to find out where the voltage loss is and repair it or replace the wire.

I once repaired a man’s Dodge Pickup with this issue. His battery had literally exploded and the new one was too hot to touch when he arrived at the shop. He only had 10.5 volts at the external regulator. Turns out he had installed a stereo and in his quest for a key hot source under the dash he had tapped into the voltage regulator feed wire. The radio acted as a giant resistor causing the regulator to see low voltage. The regulator in turn instructed the alternator to charge-charge-charge! as it sensed that the battery was dead. The result was 18.5 volts and 65 amps being pumped into the already charged battery. This could also cause the alternator failures he is experiencing as they will literally burn themselves up, especially the large capacity units he mentions—100 amp and now upgraded to 150 amps, which by the way, his Volvo should not require unless it has a large bank of fog lights, a snow plow, electric hydraulics, etc. Once the problem is resolved, he should be able to use a factory recommended amperage unit, although he may not want to give up the money he paid for the 150-amp unit. It will work fine, but shouldn’t be necessary.

To recap: test battery charge voltage with the engine running; test for battery voltage at the alternator output and regulator input terminals, and check/test for a good ground from the alternator to the engine, engine to body, and body to battery. You can also test for voltage drops by taking the voltmeter and touching each end of the wire and looking for a reading, or use the ohm setting and test it for resistance. These tests will help you diagnose and find bad connectors, wires, etc. Start at the extreme ends of the wire or cable, then work your way closer and closer until the resistance disappears. Now you have narrowed down your search to a few inches. Also do these tests on either side of a connector or splice, and you will often find corroded connections this way.

Another simple test is to make some long test leads out of 12- or 10-gauge wire and attach them to a suspect circuit, such as alternator case to battery negative, or alternator output to battery positive, etc. You can also use a small pin pushed through a wire to test for voltage or to connect the test lead to. By doing this, you bypass the suspect circuit. If it corrects the issue, you have identified the problem; now you have some more diagnoses to do.

The easiest test for voltage draw is to remove the positive battery cable and insert a test light in series from the battery post to cable end. It should not light or light dimly. Even in newer cars there should only be a few milliamps of draw to operate the computer memory, radio presets, clock, etc. If unsure, install an amp-meter in series but make sure it is rated for 5-10 amps of draw so you don’t ruin the meter. If you see a draw of several amps, there is a problem such as a glove box lamp, trunk lamp, etc that is staying on, but these small drains would not cause the alternator problems he is experiencing as the loads are not large enough to cause alternator failure.

And maybe I should have mentioned this first: Have the battery tested (also as you suggested). A dead cell will also cause the problems he is having as the alternator tries to charge a battery that will never get fully charged.

Daryl Conley Truth or Consequences, New Mexico

First thing that popped into my head reading the question was how is the alternator failing? Maybe it’s not directly electrical. Maybe the alternator pulley and the drive pulley on the engine are not coplanar. This could be causing undue stress on the alternator, driving it to an early grave. This might be particularly true if it’s a Ford block and a Volvo alternator with a possibly homemade bracket.

Adam Fisher West Hartford, Connecticut

There is a simple reason why Peter Harding’s alternators are failing. The simplest reason is one that bit me many years ago. Oddly enough it was on my wife’s 1974 Volvo but it could have been any car. The battery died and I replaced it with a new one. After a few weeks it was dead again. The ALT light was not on, but when I checked the voltage on the battery with the engine running it was only 13 volts. It should be 14.

I replaced the diodes in the alternator. No fix. I replaced the regulator. No fix. I replaced the alternator. Still no fix.

I finally touched the pulley on the alternator after shutting off the engine and it was hot as blazes. It was only then that I realized that the V-belt that drove the alternator was worn so narrow that it bottomed out in the pulley groove. The belt looked like new. It was tight; in fact, very tight. But it could not get enough grip on the pulley to do anything except turn off the warning light. My wife always drives with her headlights on so the battery would slowly run down.

Carl Bauske Charlottesville, Virginia

Editor’s Note: Regular readers will recognize Carl as an AR contributor and Volvo owner himself.

I’m not sure where the alternator ended up in this conversion, but on my E-Type Jaguar the alternator is very close to the exhaust. There was what appeared to be a shield that protected the belt and pulley.

When the mount on this shield broke I did not replace the shield right away, assuming I was smart enough to keep my fingers out of the belt and pulley.

Then I started frying diodes in the alternator.

Fortunately, they were the types that were replaceable with identically sized Chrysler diodes, but the real problem was heat build-up due to the lack of the “belt” shield. That “belt” shield was actually an air funnel that allowed cool air to be focused around the back of the alternator, and keep the hot exhaust air away. So be sure the VolFordo alternator is getting plenty of cool air or change the mounting location.

Paul Ruimerman Via email

Peter Harding is tired of replacing alternators (and about ready to give up on the car). When I was a young mechanic I came across an older mechanic who was having the same problem with a customer’s car in his repair shop.

The customer’s car was a ’60s model that had the regulator mounted on the inner wheel panel. He had replaced both the alternator and regulator many times under warranty and was at a loss for a solution. Basic testing (that he had done repeatedly) showed good connections on the battery, alternator and regulator.

He then talked to the customer to get the rest of the story. The car had been in a fender bender and the body man had painted the fender, the inner panel and other parts before putting the parts back on the car. The regulator was grounded to the inner panel but there was not a good ground through the inner panel back to the battery.

Daryl Koch Via email

I have been a generator and starter rebuilder since 1960.

Concerning the multiple failures on the Ford into Volvo swap I am going to wager that it is a Ford alternator being used. Ford alternators have fed my family for years due to the short lifetime of many of them.

I would put a 10SI Delcotron on this car so he can enjoy it for many more years of driving. The 10 SI has from 55 amps to 108 amps and is easily installed with just a wire from an idiot light to energize it.

Many have been converted to one wire for street rods for years. My only hesitation on the one-wires is you have to rev the engine which forces the alternator to charge while the two-wire charges immediately with the signal from the idiot light.

Rich Gabrielson Hornbrook, California