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Blower Fan Electrical Load

mickd's Avatar
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11-03-03, 10:41 AM   #1  
Blower Fan Electrical Load

I recently completed a head gasket replacement on my 1987 Chev Suburban 5.3 L with TBI (coolant leak from overheating when heater core failed). Everything appeared to be ok. The weather has now turned cold which requires me to use the heater.

When I turn on the defrost with the blower fan and the truck at idle, I can hear belt squeal which goes away when I increase the throttle (but will come back). I then let if fall back to idle and notice on the voltmeter that it drops well below 13 V. In one case, while pulling away, the truck stalled.

Turning on the lights doesn't appear to effect the alternator load (I guess its really charging voltage).

It appears that if I lower the blower setting from max to a few steps below, the load on the alternator remains above 13 V.

My questions are

1) Is the high load indicated by the alternator indicating that the fan is getting ready to fail or is it the alternator getting ready to fail?

2) Belt tension appears to be good, but should I try tightening it up more?

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Desi501's Avatar

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11-03-03, 06:51 PM   #2  
Most likely it is energizing the A/C compressor coil in the defrost mode to remove moisture. It wouldn't be unusual for the compressor to draw like that.

mike from nj's Avatar
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11-03-03, 08:13 PM   #3  
mike from nj
low voltage+squeeling belt=loose alternator belt

the easiest thing right now is to tighten the belts, defrost calls for the compressor to come on, old stiff belts are more prone to making noise, even if tight, try unplugging the compressor plug and see if it makes a difference.

how old are they anyway?

to find the noisy belt, squirt a small amount of WATER on to the suspected belt and it will usually quiet it for as long as it's wet, then come back with a bigger noise when it dries in a few seconds. if the belt is way too loose, the water will make the belt slip even more, but should still be quiet.

let us know what you find

Joe_F's Avatar
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11-04-03, 09:38 AM   #4  
If the belt is over 4 years old, throw it out, way overdue for replacement. Only use good quality Dayco and Gates belts.

I assume you mean 5.7 TBI as there is no 5.3 in this year.

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