Annoying Fan!!! 97 GMC Truck

Did you buy the right clutch? You need to specify with or without A/C and the rear-end gear ratio when you buy it to get the right one. Also, did you buy a heavy duty model?

Doc

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Doc,

Right off I'd like to thank you for all the help you are always so willing to give here.

Curious about the rear axle ( gear ratio) statement from the above. Never saw that as a requirement for a clutch fan. I understand the engine turns more revolutions per mile driven, but how does that change the fan clutch specs?

Al

They usually come in two versions for GM trucks 3.42 and numerically lower,

3.73 and numerically higher. Basically a fan clutch is gunna kick off at a certain rotational speed as at that point the truck is moving fast enough that the fan isn't doing much anyways.

Trucks with 4.10's require a higher RPM cutoff as they are moving much slower at a given RPM than a truck with 2.73's. So, if you were to get the wrong fan you might see it staying engaged too long or not long enough given the circumstances.

Ya know, I just did a parts lookup and that doesn't apply to his model year. I believe it was in 95' they switched over to fan clutches that weren't partial to rear-end ratios.

Doc

Doc,

Can you confirm something else fan related? Someone told me on cars and trucks with electric AC condenser fans, the fan shuts off at some preset MPH. Is that true?

Al

I dunno to be perfectly honest with ya! It would make sense as after a certain MPH the incoming air would be pushing the fans faster than their motor and could burn em' out real quick.

Doc

most of the cars I've dealt with in the past which had electric fans worked this way. with the A/C off the fan comes on purely by temp. once the A/C is engaged the fans either run continiously or they run when the compressor is engaged. Never heard anything regarding a fan that cuts off based on mph.

In general electric radiator fans are controlled by two factors. engine temp and / or if the A/C is on or off.

I have a 92K1500 with a 350 and I put a HD GM fan clutch on it some time ago. The parts book I looked at only offered two models for the 92K1500 one was a "regual" version and the other was a HD version ( i assumed HD meant heavy duty).. I bought the HD version and it works fine. I does engage and you will hear some air flow across the radiator but I guess thats just by design.

Well, I have no idea what you all are talking about. I just went to the auto parts store and asked them. They did ask me if it had A/C and it does so I told them yes. Then they gave me the part. A friend of mine has an 85 K10 Blazer that he put a Vortec 350 in (just like mine). He went to replace the fan clutch and his makes the same noise!

I think that it would be alot easier to get an electric fan.

Does anyone have a dual electric fan for sale that is under $150?

Nice try! A decent electric fan that pulls the kind of CFM's required to cool a truck radiator will run you at LEAST $300, more like $400.

Doc

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Well, Advanced Auto Parts sells one for $189. Do you not think this will be good enough? What are CFM's?

Not, not good enough. CFM=cubic feet per minute, how much air the fan is physically moving. You want at least 4600 CFM's. The ones they sell at Advance for $189 pull 1600 CFM's IIRC.

My advice to you, if the fan is noisy it means it working, and it will be quieter in the cooler months. Just leave er' be.

Doc

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I definately welcome the sound of my fan in the KY heat... my truck's temp has been creeping creeping up at idle w/ the AC on.. I guess it's time for a flush and fill.

-Bret

Ya know what Bret, mine's been doing the same damn thing ever since I switched from R-12 to 134a. The condensor gets much hotter with 134 than it did with 12. In my case, flush and fill, new fan clutch and t-stat didn't accomplish shit.

I'm actually looking into a HD 4-row radiator to bleed off the execc heat is't getting from the condensor.

Doc

Retrofit r134A conversion condenser my friend!

Maybe one from a later year will fit right in there, without any modifications?

speak to Guy.

They're where I get all my stuff from, 30% below jobber. Technical help all you need. National distributor for: AC/Delco Motorcrap, Mopar, Nippon, Nipponseiki, and all the other foreign shit you can ever imagine!

Refinish King

yeah, mine never did it with R12 either.... I'm going to take a drive down to the local yard and see if I can find a HD radiator out of a

454 truck...though I'm not sure it's any different than the HD cooling group my truck came stock with... I don't have the $$ for a AL radiator right now.

but for now I'm going to go pick up a fin comb and F&F the rad as it's due for it anyways... maybe it'll help.

-Bret

I really doubt it.... the AC systems seemed to change yearly... the only thing similar between my '88 K2500 and my bro's '93 C1500 is the R4 compressor, the plumbing is completely different.

may have to look into it.

-Bret