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10-09-2002, 01:05 PM
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#1 |
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Registered User
Join Date: Feb 2001
Location: USA
Posts: 2,613
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Fan- High Speed Relay
My heater fan only works intermittantly on high speed. Is it the first sign the relay is going bad?
Damn- I just replaced the thing last winter. Who sells quality electrical parts ? I don't remember which vendor I got it from, but it's not a expensive part. |
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10-09-2002, 02:48 PM
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#2 |
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Senior Member
 
Join Date: Jun 2000
Location: Texan in Iowa
Posts: 2,522
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Sounds like a rheostat problem to me. It is the thingy
 that controls the fan speed via three different circuits that offer three different levels of electrical resistance to make the fan spin. I think I've heard some ppl refer to it as a relay but it's not really. You'll find it in your heater duct work behind (if you're looking from the pass. seat) and below the glove box liner. It's a little fiber plate with some coiled wires on one side and electrical connectors on the other. I think the LMC catalog may show a good diagram of its location. Good luck. 
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Ben '68 Chevy C10 Custom LWB 327/TH400 2nd owner '16 GMC Sierra 1500 SLE Dblcab 4wd 5.3 |
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10-09-2002, 06:10 PM
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#3 |
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Registered User
Join Date: Dec 1999
Location: Austin, TX, USA
Posts: 7,717
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Leinie, If you have recently replaced the high speed relay (that doesn't mean it's not bad again, but...) could be either the switch itself, a bad ground to the relay (should be a jumper from the plastic box where relay mounts to the cab) or a sign your blower motor is on the way out. Also, just check the connection to the blower motor itself and make sure it is clean. The hot wire resistors in the heater box only control the fan on low and medium.
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44 Willys MB 52 M38A1 64 Corvette Coupe 68 Camaro 'vert LT1 & TH700 69 Z/28 355 12.6's @110 69 Chevy Short Step 4 1/2"/7" drop 72 Jimmy 4WD 4spd 4" & 35's 02 GMC 2500HD 4x4 Duramax |
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10-09-2002, 07:14 PM
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#4 |
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Registered User
Join Date: Oct 2001
Location: Grapevine, Tx.
Posts: 2,142
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I would say that the ground that MikeC referred to would be the first thing to check.
It seems that the ground wire is a little shorton hte harness. Mine had actually broken. Easy test is to take a short legnth of wire and ground the high speed relay. My symptons were Low =low, Med=Med and High=low Have fun and let us know your fix.
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John Hutchison Grapevine,Texas 68 1/2 t swb 68 Mustang 69 Jaguar 71 1/2 t swb 88 Supra CompTs6m 93 Escort GT 2005 Corolla XRS |
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10-09-2002, 08:07 PM
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#5 |
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Registered User
Join Date: Jun 2002
Location: Knoxville Tenn.
Posts: 3,058
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high speed
Also check the large red wire to the left of your fuse block. Sometimes it is a 2 into 1 at the fuse and this connection will get loose and heat up causing a bad connection. If it looks burnt this will more then likely be your problem. ( found this to be the case many times.)
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56 Chevy Bel-Air 2dr. HT (purchased new) 71 Chevy Cheyenne SWB PU (502HO) 65 GMC short bed step--work in progress and my gofer |
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