My 2013 Avalanche starts to have low battery problem about a month ago. After recharge the battery with an external wall charger overnight, I found the voltage drops below 14V after driving it for about an hour and keeps dropping. So the alternator is not charging the battery.

I think it's either the voltage regulator, the rectifier, or both inside the alternator. My alternator is DR37 (cast on housing). When I tried to find a voltage regulator for it, I found one for DR44.

My question is can a DR44 voltage regulator be fitted into a DR37? Some website says this may need some modification on the alternator. Do you know what kind of modification this is?

I am thinking using something more heavier duty than the original one when I do this repair so I will not need to do it again.

Thanks for your help!

 

When I looked inside the DR37, I saw black colored wires. I don't know what the original color is, but it's usually dark brown kind. So I assume the wires are burned a little bit that's why it works only when it's cool.

I bought a DR44 on eBay and found DR37 and DR44 have identical mounting dimensions. So it's a direct drop in replacement. The pulley center maybe a little bit higher than before but the tensioner can take care of it.

So my recommendation is to use a DR44 to replace your DR37 when it's broken. This way you don't need to worry about it later.

 

Has anything else ever occurred . when driving around with the change you did?

 

It works fine. But I found the low charging voltage is caused by temperature control: it happens only when it's hot in summer time. The control set the voltage on the alternator too low with high temperature. So this has nothing to do with the alternator. But I have no idea where this control is.

 

Anybody knows how to bypass the temperature control on this alternator to let it output maximum voltage? I found the voltage is low whenever the headlight is on. Thanks!

 

how low?

 

Without headlights, it's over 14V. But with headlights, it drops under 14V. It's also getting worse when ambient temperature increases. I think there is a control from the car to the voltage regulator inside the alternator which tells how high the voltage based on temperature in order to prevent overcharging the battery. And there is something wrong with this control. But I don't know how to verify or fix.

 

how much under 14V? What did you measure it with?

 

I just tested it: when I first start the car cold, the voltage is around 14.98; soon (less than 5 minutes under Texas sun, 80F) it will drop to around 13V. My old DR37 was doing the same before I replace it with a DR44. So the problem is not the alternator, it's the control signal that is sent to the alternator.

 

Why do you want higher voltage? Your charging system is working how it should. Leave it alone.