Alternator overdrive pulley question

[willyt4r]

With the high heat and heavy traffic in smoggy California, I find myself paying a lot of attention to the temperature gauge when I am stuck in traffic with the A/C blasting, music playing. and electric cooling fan. I did install a high output alternator for just this scenario. But when the RPM,s are under 950 with the heavy electrical load, the amp gauge reflects lower voltage. The problem is the cooling fans are not turning fast enough dissipate the heat soak. If a rev it up to 1100- 1200 RPM's, turn off the A?C and music the temperature returns to normal. Regular driving - no issues.:usa2:

Denso alternator pulley specs - 15mm bore 4 groove 2.5 inch .
I found a overdrive alternator pulley that is 1.9 inches, which should result in 900 more rpms from the alternator. STARTERS AND ALTERNATORS
I am interested in opinions and feedback on the alternator overdrive pulley modification.

 

[KidVermicious]

What output is your alternator supposed to be, vs. it's actual output? What's the amp draw on your sound system and electric fan? Have you checked your wiring for bad power or ground connections? Before you mod, make sure everything is working correctly first. And then I'd consider going back to a stock fan clutch instead of the electric fan.

 

[fourwd1]

Your electric fan may be drawing more current than your "high output" alt can supply at low RPMs (which is actually very common, they usually don't).
You may want to try the stock fan as suggested and see what happens before changing even more things.

 

[dorton]

Whats the voltage range when all acc are running, and the fan is on?

 

[77'911]

With a new factory rad (brass/copper, multiple core) in our 1990 (3VZE, auto) with the A/C on in an hour of stop/go traffic, the temp gauge never moved off center. Now, we're in the PNW which is probably a tad cooler. Having said that, the temp gauge should not be moving up like it is on your truck. Your rad might be loosing it's efficiency or the fan clutch might be worn out. You might address the over heat issue before addressing anything else.
regards

 

[KidVermicious]

Your rad might be loosing it's efficiency or the fan clutch might be worn out.

It's an electric fan, there is no clutch.

 

[77'911]

It's an electric fan, there is no clutch.

Ah, no surprise it's over heating. The original units take some power, but they flow a lot more air reliably through the rad. This is a common issue for guys who remove the factory fans from older BMW's. The relay and temp switch structure is not sensitive enough to handle the temp swings and spikes. Each to their own though.
regards

 

[willyt4r]

voltage report

At idle the voltage is at 12 volts at 1100 rpms 13.4 volts.
After reading more on the electric fan mod,I did reinstall a new fan shroud. It does draw the air more across the engine.
It hasn't been 100 degrees So i haven't had any temperature rise issues lately. we shall see what happens during the week- if the shroud makes a difference in the heat soak.
I originally did the electric fan mod because of what I read on the forum.

 

[KidVermicious]

At idle the voltage is at 12 volts at 1100 rpms 13.4 volts.

Here's your problem. You should have over 14 volts at idle. I go back to what I said up top, check your wiring connections. Clean and reterminate the Big Three grounds and both sides of the voltage wire coming off the battery. If that's all awesome and you're still only getting 12 volts, it's a bad alternator.

 

[willyt4r]

overdrive pulley installed 14.4 @ idle

I did install the 1.9 inch overdrive pulley.. I now have 14.4 volts at idle.
There was slight corrosion in the terminal plug just a little contact cleaner and Di-electric grease. There was plenty of slot left in the alternator bracket so I didn't have to buy a shorter belt.
Thank you all for your responses and ideas.
Willy:lookout: