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HELP! Reinstalling serpentine belt on Chevy P-30 (454 w/ac)
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Hi there!

I recently had to replace the alternator on my parents 1989 Safari Trek. (Chevy 454 with AC) The serpentine belt fell off in the process and I am desperately in need of a diagram to put it back on. My vision to the front of the motor is also greatly inhibited, so if anybody has any other advice or pointers to help me complete the job, it would be GREATLY appreciated!
 
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I took this page out of the 1997 Chevy Motorhome service manual. In this case, this image is supposed to be from 1985½ to 1997. With or without a/c and with or without airpumps.



I found this 454 serpentine routing on the net



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Posts: 7107 | Location: Newburgh, New York | Member Since: 05-10-2003Reply With QuoteReport This Post
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It seems that the belt routing was a compromise at GM. On my '87, both the crankshaft pulley and the power steering pump pulley have 3 grooves, and on the crankshaft, only 2 are used. So it seems that at one point in the design cycle, the intent was to have 2 v-belts between the crankshaft and the PS pump.

But GM also had to drive the upper AIR pump and the AC compressor. Maybe due to groove offset reasons, GM chose to drive the upper AIR pump from the PS pump.

The water pump pulley supports the 1 serpentine belt, and then has 1 v belt. If this pulley supported 2 v belts, it would probably enable better belt routing ideas.

The Sanden AC compressor has 2 v belt grooves.

Matt


1987 Barth 27' P32 Chassis
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One technique to figure out is to look at the pulleys; those to use the front (inside) of the belt will be grooved; the back, smooth.

The idler pulley will always be on the back of the belt.


Rusty


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Thank you Bill, Matt and Rusty. I was able to get the belt restrung and mounted!

Which now leads me to the second problem: The output of the new alternator is weak. There is obviously a short somewhere dragging it down, which is why the last alternator died. My question is, are there common places to look for the short? Or am I doomed to tracing the wiring inch by inch???
 
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How do you know the output is weak? What happened to the last alternator? If there is a short, a fuse, breaker, or fusible link should have opened. My first assumption (having had multiple decades old vehicles) is that there are grounding problems between the engine, the frame, and the battery. If your alternator isn't seeing 0V where it should be, it will not output 13 or 14V where it should be.

Also, in the timeframe of the production of your vehicle, GM put several different models of alternator on the 454. One of them has a remote sense line to check the +V. This should be checked for clean contacts also.

Good luck!
Matt


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Matt,

I know the output is weak because the dashboard gauge only registers 9v with the engine running. I confirmed this with my digital voltmeter connected directly to the alternator and ground (it registered 10v). The last alternator died after only a few hours of operation. I checked ground between the engine block and frame, and it measured near zero resistance, as it should. Is it possible a bad isolater or v regulator could be to blame?
 
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Hi Rio!
"I know the output is weak because the dashboard gauge only registers 9v with the engine running."
I don't think you can be sure that the output is weak, without a few more tests. What is the voltage on the dashboard gauge when the engine is not running? What is the voltage on the dashboard GND connection, relative to battery GND, with and without the engine running.

Also, if your dashboard GND is not at 0V, your fuel gauge will not properly indicate fuel level. (I can attest to this at midnight, somewhere in Idaho, last summer)

"The last alternator died after only a few hours of operation." Could you get a parts shop with a tester to tell you if a coil or the regulator failed?

"and it measured near zero resistance, as it should." That is with a volt-meter, under a condition of forcing a few milli-Amperes through the connection paths. The resistances shown by the corroded connection points are not going to be perfectly ohmic. At 50 Amps loading, you might find a different story about the resistance. Galvanic corrosion and the interface of dis-similar metals are going to do strange things after 20 years.

Does your dashboard radio work OK?

First thing to try, take the isolator out of the circuit and see what happens. On mine, the isolator is attached to the aluminum body, with steel screws. The aluminum body is attached to iron framing, with bolts and/or rivits. This is in turn bolted to the vehicle frame. Every step of the way adds trouble for good grounding.

I think I recall that I had a CS130 Delco alternator, and this has a sense line which went to the isolator. This has to be dealt with as well, and serves as a remote sense for the +V.

First thing, when the engine is running, start taking out the fuses and see if any particular circuit causes trouble. Try headlights on and off. Try the horn. I think if there are failures in the relays for those circuits, you could have a power drain.

Adding new ground lines between the battery, the frame, the engine, the isolator, and the dashboard might be worthwhile.

Good luck!
Matt


1987 Barth 27' P32 Chassis
Former State Police Command Post
Chevrolet 454
Gibson Exhaust
 
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I'll check all that out and let you know!
 
Posts: 6 | Location: Arvada, Co. | Member Since: 05-28-2010Reply With QuoteReport This Post
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Alternator problem solved! Again, thanks to everybody who made suggestions. The problem was in a broken fuse in the fuse box. After growing very frustrated in searching-out wiring harnesses, along with verifying the v regulator and isolator were good, I decided to check the fuse block underneath the drivers' side dash board. I found a burnt fuse marked 'gauges' (10 A) and replaced it. When i then fired up the engine, all charging characteristics were restored to all batteries. I verified this by again useing my DMM to check output from the alternator itself, as well as charging voltage to all of the batteries. Everything is fine now. Why a fuse that only routes power to the dash-board would affect the entire charging system is a mystery to me, but that is what happened. I have also included in this post a serpentine belt diagram for my 1998 chevy p-30 chassis 454 V8 vortek fuel injected engine w/AC, for future reference, which was the original problem. Again, THANK YOU ALL!
 
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quote:
Originally posted by Rio:
I found a burnt fuse marked 'gauges' (10 A) and replaced it. Why a fuse that only routes power to the dash-board would affect the entire charging system is a mystery to me.


Does your dash have an idiot light for charging?


.

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No.
 
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Voltmeter? Ammeter? How do they behave before and after fuse replacement?

You might want to also take the fuse out and check for continuity to GND, battery +, and alternator +.
Matt


1987 Barth 27' P32 Chassis
Former State Police Command Post
Chevrolet 454
Gibson Exhaust
 
Posts: 279 | Location: Massachusetts | Member Since: 07-28-2006Reply With QuoteReport This Post
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    Forums    Tech Talk    HELP! Reinstalling serpentine belt on Chevy P-30 (454 w/ac)

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