Alternator Belt Keeps Breaking

mustu521 · December 19, 2014

Hi guys,

I have a Mazda BG familia 91 which keeps snapping alternator belts quite often. After replacing a new belt and driving for a few weeks or month the belt becomes loose and alternator doesn't charge properly. Then belt needs to be adjusted. Then again after sometime it becomes loose. This keeps repeating until the belt finally breaks.

This car has two belts. One drives the alternator and the waterpump and the other drives the ac and power steering. The ac and ps belt is fine.

Any ideas and pointers where to start looking?

jaga · December 19, 2014

Check 1. condition of the pully. 2. Allignment 3 .Quality of the belt.

Rumesh88 · December 19, 2014

In addition to what jaga has suggested above check if the V-groove is polished all the way to the bottom on both pulleys (crank pulley in particular) and the belt. When a new belt is installed the belt should not touch at the bottom of the V-groove on the pulley and vice versa.

The Don · December 19, 2014

What is the brand of belt you are using?

I had a similar experience on the belts on the same car, and switching to a different brand of belt sorted it out if I remember right. Also check if all the items connected by the belt move freely without play and the belt is tightened to the correct tension and not too tight.

mustu521 · December 19, 2014

Hi Guys,

Thanks for all your suggestions.

Both the alternator pulley and water pump pulley turn freely without any play. I took the car to an electrician down zoo road and he advised me to change the alternator pulley. The pulley appeared to be rusted and a groove had formed in the center section. Only the grooved was polished. This was the most likely cause that was found. Unfortunately there were no replacement reconditioned pulley for this model, so had to go to a lathe to turn one out. The guys at the lathe turned one out from scratch to the exact measurement of the original. It's a one piece pulley as opposed to the two part flange type that came originally.

Let hope this solves the problem once and for all. I tried Bando and Mitsuboshi brands of V belts but didn't find much of a difference. The one I replaced this time is a Bando. Will keep you'll updated on how things go.

mensoft · December 22, 2014

Hi,

I had exactly same issue and couldn't run the belt at least 500 km. and the battery charging issue when headlights on.

when I went to electrician he removed the pulley and polished it with the machine. cost me about 2000 and so far no issue.

tiv · December 22, 2014

The brand also makes a big difference, try to get oem or closest, Mitsuboshi is good for the older ones, recently I saw a belt change done in a swift, It disintegrated within one week, powdered bits all over the engine bay

perfect pulley (thoroughly checked) and no more than adequate tension (checked by many people), they seem to be importing sub standard belts and scamming buyers

The correct Tension also matters as I've personally seen an order of 21 Water pumps and belt kits (genuine) for 21 LR Defenders (Tdi) by the forces due to one faulty mechanic going overboard with the tension.

mustu521 · January 31, 2015

Hi Guys

Here's an update to my issue. After turning out a brand new alternator pulley and replacing it along with a new belt the problem returned after a few weeks!!. Yes same old problem about the belt slipping and battery not charging.

I took the car to Nishantha's garage (auto electrician) and after looking at various things his diagnosis was that the alternator was bad and needed to be replaced and only then further diagnosis can be made.(he noted it was unusually hot) I wasn't too happy with that as the financial damage was too high just to rule the alternator out. I decided to do my own investigations as for some reason i wasn't ready to replace the alternator specially when it was working fine.

After a detail looking around at the alternator, pulley, belts and wiring during a weekend I made a startling discovery!. The main battery wire that goes to the battery terminal was loose!. The place where the cable joins the connector it has two screws to hold it in. I found that it was holding only on one screw and that too the threads were worn and wouldn't tighten. I decided to fix it by rotating the terminal so that the other unused screw came in first contact with the wire and tightened it properly. I started the car and checked the voltage which was around 13.9v and with lights and AC running it remained at that. Reving the engine raised it to about 14.2v.

It's been about a month now and I don't have anymore belt issues. I think I've fixed the root problem. What was happening all this time was that due to the loose connection in the battery terminal the battery wasn't getting charged effectively. This was causing unnecessary load on the alternator which caused it to overheat. This was then destroying the drive belts prematurely. I will monitor the vehicle for a few more weeks and if the problem doesn't return then the above diagnosis is correct.

It is unfortunate that most of our mechanics are always interested in quick fixes and want to perform trial and error at the clients expense. Had the mechanic spent a little more time in diagnosis he would have found the problem as I did.

Rumesh88 · February 1, 2015

On 1/31/2015 at 3:37 PM, mustu521 said:
Hi Guys
Here's an update to my issue. After turning out a brand new alternator pulley and replacing it along with a new belt the problem returned after a few weeks!!. Yes same old problem about the belt slipping and battery not charging.

I took the car to Nishantha's garage (auto electrician) and after looking at various things his diagnosis was that the alternator was bad and needed to be replaced and only then further diagnosis can be made.(he noted it was unusually hot) I wasn't too happy with that as the financial damage was too high just to rule the alternator out. I decided to do my own investigations as for some reason i wasn't ready to replace the alternator specially when it was working fine.

After a detail looking around at the alternator, pulley, belts and wiring during a weekend I made a startling discovery!. The main battery wire that goes to the battery terminal was loose!. The place where the cable joins the connector it has two screws to hold it in. I found that it was holding only on one screw and that too the threads were worn and wouldn't tighten. I decided to fix it by rotating the terminal so that the other unused screw came in first contact with the wire and tightened it properly. I started the car and checked the voltage which was around 13.9v and with lights and AC running it remained at that. Reving the engine raised it to about 14.2v.

It's been about a month now and I don't have anymore belt issues. I think I've fixed the root problem. What was happening all this time was that due to the loose connection in the battery terminal the battery wasn't getting charged effectively. This was causing unnecessary load on the alternator which caused it to overheat. This was then destroying the drive belts prematurely. I will monitor the vehicle for a few more weeks and if the problem doesn't return then the above diagnosis is correct.

It is unfortunate that most of our mechanics are always interested in quick fixes and want to perform trial and error at the clients expense. Had the mechanic spent a little more time in diagnosis he would have found the problem as I did.

Good observation if it actually solved the problem. The only way this can happen is that while running, the battery connection may go on repeatedly connecting and disconnecting thus creating an abrupt load/no load condition on the alternator.

Edited February 1, 2015 by Rumesh88