LT1-LT4 Modifications 1993-97 Gen II Small Block V8

Fan wiring diagram

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Old 06-25-2007, 03:51 PM
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Question Fan wiring diagram

any suggestions on where i could find wiring diagrams on my 93 T/A? I am trying to figure out why my fans will not turn on by themselves. I replaced the relays, and the senson in the waterpump and the one right under the head(sending unit for gauge cluster). I know my fans function because i have a SLP designed (home made) manual fan swith and the high and the low speed both work. I do own a Hayes Book for my car, but my buddy still has it from us getting his 98 Z-28 back on the road. I would go pick it up but the weather in my area has kinda kept me in my house. So any suggestions on websites would be greatly appreciated.
Old 06-25-2007, 03:53 PM
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i found mine at gearchatter.com.,,,,,,,but mine is a 2000.
Old 06-25-2007, 03:55 PM
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did it help you figure out why yours was not turning on by the pcm alone. Or were you having the same problem?
Old 06-25-2007, 04:08 PM
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another thing that i had a question about is that i have read that people say that the 93 only has one speed for the fans (only two relays). Mine on the other had has both a high and a low speed. When i connected the manual switch i can click it one way and only on comes on. When i click it the other way both fans engage at a higher speed. I have 3 relays in the electrical box under the hood. Any suggestions that might help me. Because I am lost big time on this one.
Old 06-25-2007, 04:47 PM
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Go to www.shbox.com and there are all the schematics right there in the wiring section.
Old 06-25-2007, 04:48 PM
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wel that one is fr a 95 and mine is a 93. Dont know if it make to much difference. But figured i wouldfind out first
Old 06-25-2007, 05:50 PM
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The 93 fans are one speed. We have to fans, a primary and secondary. The 95+(maybe 94+) are dual speed fans.

Have you tried turning your AC on? This will force both fans on. Are you sure you didn't unhook the factory wiring when you wired your manual switch?
Old 06-25-2007, 06:41 PM
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If they're single speed, why the triple wired plugs? Usually that's for twin speeds. One ground, 2 power. Unless I'm REALLY not remembering the plug right, but I just unplugged it a couple weeks back, so it's pretty fresh in my mind.
Old 06-25-2007, 07:04 PM
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If it has 3 relays, its 'high' 'low' fans.
I have the exact same problem, fans work fine on a manual switch, but no kick-on by the computer.
I traced mine to the PCM, when the car is overheating, the PCM is only seeing 184 deg so it doesn't turn the fans on. You might want to hook a scanner up and check the temp the PCM is reading.

Sara Lou
Old 06-25-2007, 07:54 PM
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What kind of scanner would i be able to hook up to it since it is a 93 ecm OBD I? And the ecm is new, out in a month ago
Old 06-26-2007, 01:30 AM
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find out if your even getting power to your relays (test lite) if you are run a jumper for "testing purpose" in the relay

Last edited by streetwarrior96; 06-26-2007 at 01:48 AM.
Old 06-26-2007, 02:49 AM
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I use an AutoXRay scanner, and it can even data log, if I had the computer link to download the log It can do real time scanning of everything though. I leave it hooked up while I drive and if I get bored turn it on and check sensors

Resembles this one, but not quite. http://www.obd-codes.com/reviews/dat...2000-large.jpg
Old 06-26-2007, 05:58 AM
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Any of the OBD1 scanners should 'read' your computer, I used Datamaster (free for first 20 scans). If I remember right, on the '93 you can jumper pins 'A' + 'B' on the diagnostic terminal (under steering column) to get the codes, and it should also kick the fans on which will tell you if the relays, wiring, fan motors, etc are working ok.

Sara Lou
Old 06-26-2007, 08:53 AM
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my fans and everything do work. When my SES light comes on both of my fans kick on. I have a manual swith in my car for the fans with the LED. When i turn it to the left the fan kicks on, when i click it to the right both fans kick on. When i have the switch in the off position and the ses light turns on then both lights; both fans; turn on. The only time they wont turn on is when my car reaches the point at which the computer is sapposed to turn it on.
Old 06-26-2007, 07:19 PM
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Sounds like you got the same problem as me then. Or the sensor in the water pump might be giving a false reading to the PCM. If you go to shbox.com he has a list there of what Ohms relate to what temperature that the sensor is sending.

Sara Lou
Old 06-26-2007, 07:24 PM
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Ohh, and the diference in the '93 and '94 fan setup. your low speed is one fan running, high speed 2 fans running. On my '94 low speed is both fans running at a lower speed, then both running at full speed for high setting.

Sara Lou
Old 06-26-2007, 08:40 PM
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that explains alot then. Thanks Zralou.
And what do you do if you pcm is not reading it right? And would it be doing that if the PCM is new?
Old 06-26-2007, 09:49 PM
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Could be damaged wiring somewhere. PCM is new, so turn to what is old.
Old 06-27-2007, 05:58 AM
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If the fans come on with the SES light, that pretty much tests all the wiring, relays, etc., and the PCM is capable of operating the fans. Did you replace the whole PCM, or just the removable chip?.

The only thing I am doing about the PCM is to replace it, I picked up another on e-bay, just got to gef off my @## and reprogram it (came out of a 'B' body).
The first thing I would suggest for you is to check the Ohms readings at different temperatures at the sensor in the waterpump, then compare them to the list at shbox.com, if they are within acceptable range, then I would suspect the PCM.

Sara Lou
Old 06-27-2007, 10:35 AM
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i replaced the whole PCM




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