It's hotter than hell here in Vegas! The Shark is running a little hot and I noticed my Volt guage below 12. I had the battery checked and it's good, so I did the "disconnect the battery while the car is running" and no difference.

If the voltage is weak, would that contribute to the hi temperatures (causing the fans to run slower)?

Anyone have an idea if this could be due to the electric fan I installed a few months back replacing the clutch fan?

Thanks,

 

Darien
Low volts will cause low running speeds of many motors, including fans.

Not sure about this but I think I've heard it said that disconnecting the battery with the engine running ruins diodes or some other component in the alternator. Could be your alternator IS faulty and that's why the symptoms showed no change when you did the disconnect.

Colin. 89GT

 

Thanks Colin, now I just need to find the right ALT. There are a few on ebay but noy sure which one.

 

Darien
If you intend to do an alternator swap there was an article on upgrading to a bigger-output Bosch unit on the Australian 928 website about 6 months ago. May be still there..

Colin

 

As has been said MANY times here and elsewhere - DON'T depend upon the dash-mounted voltmeter!

First thing to do is to use a good voltmeter at the starter terminal where the alternator wires hook up, or at least at the jump start terminal.

Disconnecting the battery with the engine running will often damage the alternator. It is not a recommended test.

If the alternator output is actually low, there are several possibilities:
- Loose drive belt. The multirib drive belt should be very tight - the old "half-inch with thumb pressure" test does not apply to the flat belts.
- Open diode in the alternator.
- Faulty regulator.

If the alternator is questionable, my suggestion is to find a good local auto electric shop - not a general garage, not a parts house, but an auto electric shop that does nothing except repair alternators, generators and motors. Take them the alternator and have them test and repair it. That way, you have the correct alternator, with the correct harness and cooling cowl.

If you need an alternator and want the original, we sell a Bosch-rebuilt for $216 exchange.

 

Wally? What's the way to check and/or adjust-to-spec the belt tightness if the "1cm deflection with thumb pressure" method from the WSM is no longer pertinent?

 

The 10mm with thumb pressure check given on page 13-18 applies to the V-belts.

The flat poly-rib belts should be adjusted using Porsche Special Tool 9201 per page 13-18b.

It is worth noting that the 32-valve timing belt is set to 5 on the 9201 gauge (in whatever units that might be ), while the alternator belt is set to 8.4 - 9.2 of the same units. That is so tight that the belt feels like a solid bar.

 

I'd definitely go with the re-build Wally mentioned if it tests bad. It's usually about $100 here and they run and last like new.

 

those would be PMUs (Porsche Measurement Units...)

Sigh. Yup. That's where I thought this would go. In the absence of the 9201 PMU gauge...?

My concern would be getting the belt too tight and fragging the alternator's pulley bearing.

 

Alright, the only common denominator is the electric fan I installed. Prior to that, I had no problems with elect power, it's only 2100 CFM. I'm just curious how folks have installed up to 3100 CFM fans and not had problems. Do I need to install a beefy alternator?

 

Hi Darien,

I wouldn't worry about installing a beefier alternator, just stay with the stock unit. My 84 Koenig car is running 3 Spal fans, and 1 stock a/c fan (3 for the radiator and a/c, and 1 for the external oil cooler). And it has the stock alternator, with no problems.

I could just be that your alternator has weakened with the record heat out here.... (my old Zcar alternator just died last week, after I added an electric Spal fan to that radiator) (different car though..) However, as Wally said, DON'T rely upon the voltmeter in your dash, they can be inaccurate at times.

BTW, how'd the timing belt job turn out? (that was my belt-tension tool that Tony brought over)

 

Thanks Bill, I'll just have to test the Volts/AMPs with an external guage and see what happens. The alternator looks stock and it just turned 152,000 mi on this last road trip.

The T-Belt job went very nice, thanks for the tool

We need to hook up some time, I'm down at Raptor, look me up

 

What about bad grounds? It is worthwhile to check them all. Made a difference on my old car ('85S). The can get worse over time (more resistence or something) and cause the problems you are describing.

 

Hi Darien, welcome back to springtime.