Alternator Question

[joecool911]

My alternator output is less when warm out than when cold. Now it’s putting out 14.3 on average. When it’s hot it’s more like 13.7. Is this an indication of trouble ahead? 

[Me78569]

%100 normal for charging voltage to be higher when cold.  

[joecool911]

Ok, thanks!!!

[Killer223]

it does that to heat up the batteries.

[Mopar1973Man]

Batteries resist charge when cold. So the battery temperature sensor under the driver side battery detects the battery temperature and adjust the charging rate for the battery temperature. So on a cold morning, you could see as high as 14.8 volts DC and on a hot summers day you could see as low as 13.2 volts DC. This is all very normal. This is one of the reasons why the battery lifespan on our trucks is much higher like average of 10 years typically. 

[JAG1]

Another question.....

 

How difficult is it to change the diode bridge? You don't have to tear it all the way down do you?

[bcbigfoot]

Depends on which alt., there are two different makes the Bosch and the Denso.  The Denso has bolted in Diodes and the Bosch which I have,  the diodes are welded in (possibly soldered in) not easy to change.  I had the Alt. apart several years ago to rebuild but found it to difficult ( I have rebuilt dozens of alts over the years) decided to take it to the local alt. shop to rebuild. The alt. didn't need diodes but it did need new slip rings, brushes, and bearings. 

 

 On the bright side the Bosch diodes seem to be hardy as mine are the original and I have worked heck out of them.  The last 8 years the truck has been loaded with a truck camper and two extra 105 ah agm batteries connected via a 4 gauge charge wire I can see 130 amp charge rates for 20 mins after starting the truck after boondocking for the night, then tapering to 40 amps. for several hrs. afterwards.

[Mopar1973Man]

No. It's easy just pull the back cover off and the diodes are held in place with Phillips screws. While your there you can change the brushes too.

[bcbigfoot]

21 minutes ago, Mopar1973Man said:

No. It's easy just pull the back cover off and the diodes are held in place with Phillips screws. While your there you can change the brushes too.

 

Wish my Bosch alt. was that easy.  I might look at switching over to one if this Bosch gives trouble.

[joecool911]

Is there an easy way to tell which one you have? Does changing out the diode bridge take care of a/c noise?

[bcbigfoot]

14 minutes ago, joecool911 said:

Is there an easy way to tell which one you have? Does changing out the diode bridge take care of a/c noise?

 

The Bosch alt. has a black plastic rear cover and typically has their name engraved.   Their are pictures of each type of alt. on Rock Auto's website just to be sure.

[Mopar1973Man]

2 hours ago, joecool911 said:

Is there an easy way to tell which one you have? Does changing out the diode bridge take care of a/c noise?

 

Yes changing out the diodes pack repairs most AC noise problems. There are other issues like bad brushes and other things that could cause the issue.

 

Denso alternators tend to look smaller than the Bosch as far as I know Denso also have the replaceable diodes.

[JAG1]

8 hours ago, bcbigfoot said:

 

Wish my Bosch alt. was that easy.  I might look at switching over to one if this Bosch gives trouble.

I still have a Bosch on the shelf from the time I switched  my 2002 over to Denso. I did that because on my 1st gen truck I found those Denso's lasted.. Then 9 years later I bought my second truck, an 01 and it came with a Denso.

[IBMobile]

How to change the diodes and brushes in a Denso

 

[joecool911]

Ok, is this everything that would be done on a rebuilt alternator from the store?

Got to be some bearings in there to replace. 

[Mopar1973Man]

There are two bearings and a brush kit too. The problem is the bearings have to be pressed off and the new ones pressed on.

[joecool911]

Can the bearings be lubricated?

[Dieselfuture]

They are a sealed bearing type, you could probably try to get some oil pass the seal but I would just change them, they're not hard to do. Also when I changed diodes in my Bosch it only fixed half the ac noise I had to do brushes and slip ring to get it right. Mine were tack welded in, I soldered them back in, after squeezing them together. 

[dripley]

10 hours ago, IBMobile said:

How to change the diodes and brushes in a Denso

 

My tablet tells me I don't have permission to see this article.

[Mopar1973Man]

Should have access now being I've just approved the article...