alternator failure- Belts? guages?

hertfordnc · Post by **hertfordnc** » 05 Oct 2006, 08:11

Greetings,

The alternator on my 89 240 dies suddnely last night.

I had removed the speedo cluster to begin looing into reapiring the odometer gear and I had not gotten it all back together so the warning lights had no ground and therefor did not warn me about hte alt.

first question: was this cooincidence or could I have done something in the to the wiring while messing with hte instruments

second question; one of my two belts is missing. It was there last week. The other belt seems pretty tight but I know they put two on for a reason, could it slip that much with just one belt to cause the car to die?

peace

wojeepster · Post by **wojeepster** » 06 Oct 2006, 15:22

The alternator gets the voltage to iniatiate charging through the warning bulb. Unlike a generator that has residual magnetism in the pole pieces. Once alternator starts charging there is 12 v on both sides of the bulb so light goes out (no ground). If you had the warning light disconnected the alternator will not give you any output. One wire alternators are another animal and have magnets to iniatiate a small voltage to get the alternator going. They work without the warning light voltage but have the disadvantage that they have to reach a certain rpm before they give output. You are better off with a three wire system.

brucepick · Post by **brucepick** » 08 Oct 2006, 20:39

hertfordnc wrote:Greetings, ...
second question; one of my two belts is missing. It was there last week. The other belt seems pretty tight but I know they put two on for a reason, could it slip that much with just one belt to cause the car to die?...

Definitely use two belts. Get them in matched pairs from an import specialty parts place or a Volvo dealer parts counter. They package them in pairs for that purpose. The matched pairs are carefully matched for length - not just "close enough". Also should be from same rubber/stock batch so stretching tension etc. should be the same.

Reasoning for two belts - Primarily due to combined heavy load of the two items, water pump and alternator. Also both are critical items, if either shuts down you're not going very far.

The two belts can carry the mechanical load better than one. Also requires less tension to deliver the power to them. So less tension = less stress on the accessory bearings. Pump or alternator due to failed bearings is not fun. Less tension should also give better belt life.

Also check that the remaining belt is running parallel to the pulley grooves. If not - if running at an angle - then the alternator is sitting crooked. This will wear out a belt early and cause belt failure. BTDT.

This happens when the rubber mount bushings get worn. Alt's main mount bolt is below the alt, there's a rubber bushing at each end. There's a 3rd bushing on the belt tension adjuster - however the adjuster stud sometimes breaks when attempting to replace the bushing there so maybe leave that one alone or approach with caution and a ton of PB-Blaster in advance.