1985 300D-Changing Belts - PeachParts Mercedes-Benz Forum

Ya Mar · #1 04-17-2010, 03:23 PM

Hello All,

I had to replace my Alternator today and I thought I might as well replace the belts since they are all worn.

I loosened the tensioner screw on the alternator belt and removed the alternator with no problem.

My problem now is I can't find tensioner screws for either the powersteering or the AC belts...I can't for the life of me figure out how to remove them.

Any ideas?

Thanks!

toomany MBZ · #2 04-17-2010, 04:21 PM

The pics should help, two bolts on the front of the p/s unit, one (maybe) just below the adjustment bolt, third pic is the adjustment bolt itself. Fourth is of the A/C unit.

Ya Mar · #3 04-17-2010, 09:47 PM

Thank you for this. I'm going to try to change the belts tomorrow, hopefully it goes smoothly.

Related to the Alternator, I replaced it today and then went to an Autoparts store near where I live to have them test it to make sure it's working. They said it's reading low voltage.

They also said when I rev'ed the engine it didn't show up on their monitor, I don't know exactly how that works but the guy working there said it was strange. He wondered if something was messed up in the wiring.

Does anyone have an idea of what might be going on here? Is there something I should be checking?

When I turn off the car the second the engine dies the battery light comes on and stays on until I turn the key and take it out. Is this normal?

Thanks!

toomany MBZ · #4 04-18-2010, 07:23 AM

Inspect/replace the voltage regulator, but that usually shows up as the battery light staying on all the time and yes it's normal for it to come on when you turn the key off and before the engine shuts down.

Ya Mar · #5 04-18-2010, 12:27 PM

Thanks, TooManyMBZ, for the advice. I'm glad to hear that it's normal for the battery light to come on as the car turns off.

I'm pretty sure the new alternator has a new voltage regulator. Instead of being a rectangular box it's a little disk about the size of a couple of quarters stacked up, it says Bosch on the top. The new alternator didn't come with a new resistor, so I put the old one on the new one. I'm not sure if that was the right thing to do but that's what I did.

I'm going to look through the wiring from the Alternator to the Battery to see if anything looks out of place.

Ya Mar · #6 04-18-2010, 12:34 PM

Do you know of any quick ways to know if the Alternator is working without bringing it to the autoparts store for them to do the scan?

I still have my old battery that is dead. I was thinking I could take out the new battery and jump start the car with the old one, and then see if the lights stay on after the car is running. With the old battery the lights were not working because it was so dead. That would tell me the alternator is at least producing some electricity. But I don't want do something that could strain the new alternator.

toomany MBZ · #7 04-18-2010, 01:32 PM

There are two styles of regulator, the one you describe are the ones I'm familiar with. If you can get the car started, try this. Using a multimeter measure the battery with the car off, start it and measure again, you should read higher voltage while running.
The alternator's job is to keep the battery charged without over charging it, so the folks at the auto parts store hook it up and can measure numerous items.

vstech · #8 04-19-2010, 09:06 AM

yeah, don't hook the old dead battery to the new alternator. bad things can happen.
try this.
with car off, turn on the headlights for 30 seconds or so. then turn them off.
get a digital volt meter and measure the exact voltage on the battery terminals. it should read 12.75 or higher. if it's below 12.65 connect to a battery charger until it reads a full charge. (10A charger for 1 hour, 2A charger for 24 hours etc...) anyway, re check the lights for 30 seconds, and then measure again, if still under 12.75, battery problems are showing, check water level in each cell, and return battery to store.
if pass the 12.75 test start the car, and measure the voltage while idling. should be 13V or higher.
then rev the motor above 1500RPM, should be 13.5 or higher but below 15V
last check on the AC scale for voltage. should be 0 if it's reading AC voltage, the alternator is suspect.

disqo · #9 04-19-2010, 02:36 PM

I replaced my alternator and all of my belts last week. It was not the most fun job I have ever done. Many of the adjusting and retaining bolts for the accessories were gunked up and covered with oil, making them a little harder to locate. I also had to replace the bracket that holds the alternator to the engine, and that is not a job that I would not recommend doing unless you have to. I did find that access to many of the bolts was better after biting the bullet and removing the fan and fan guard. Removing the U shaped tube between the turbo and air cleaner was also a big help.

vstech · #10 04-19-2010, 03:00 PM

Quote:

Originally Posted by disqo

I also had to replace the bracket that holds the alternator to the engine, and that is not a job that I would not recommend doing unless you have to.

mama, sorry for all the double negatives mama.
ugh!

snookwhaler · #11 04-19-2010, 08:49 PM

Before you do anything drastic... Follow toomany MBZ advice and report back the results after using the multimeter at the battery with the car turned off and running.

If the results are low voltage while running, pull the old regulator out of the alternator for inspection (preferably with the alternator out of the car).

The brushes can "stick" in the bore causing a no or low charging condition. Also, the brushes can be broken off.... I have seen it before. An inspection of the brushes is worth it for peace of mind. Especially if you drive the car daily.

Ya Mar · #12 04-19-2010, 10:48 PM

Hello All,

I took the car back to the parts store today where I bought the alternator. They tested the system and said the new battery they just sold me was defective. They replaced it, retested the system, and everything was working properly.

I don't have a volt meter, but I watched the guy at the parts store use his and with the lights on after about 30 sec the battery read 12.84. While idling it went up to 13.93 volts.

I didn't want to change the belts until I resolved the alternator issue, so that is my project for later this week.

My next project after the belts will be replacing motor and transmission mounts.

Thanks for the advice everyone!

toomany MBZ · #13 04-20-2010, 10:20 AM

Those are good voltage readings, hopefully, your problem is solved.