C3 Vette Registry - The Best Resource on the Net for C3 Vettes! C3 Vette
Forums -> C3 Electrical
Not Logged In! Login or Register!  Users Online: 6 / Help 
Features  Find C3 Parts on ebay in only 2 or 3 clicks!  | Add YOUR C3 to the Registry

Supporting Vendors
Bair's Corvettes
Mid America Motorworks
CorvetteClothing.com
VetteBookStore.com
Volunteer Vette Products

C3 of the Month
None Current
Enter Yours Today!
Online C3 Show
13
C3s are Registered

Vanity Plates
1BADL82
73inAZ
Featured Links

Buy Now
Collector's Originality Guide Corvette 1968-1982 (Paperback)
Collector's Originality Guide Corvette 1968-1982 (Paperback)


Corvette 50th Anniversary
Corvette 50th Anniversary


Corvette Magazine - $19.99 for 8 issues
Corvette Magazine
Only $19.99 for 8 issues


Corvette: America's Sports Car Yesterday, Today, Tomorrow (Hardcover)
Corvette: America's Sports Car Yesterday, Today, Tomorrow (Hardcover)



| Hide Signatures and Profile Pics

 New Topic New Topic Post Reply Reply New Poll New Poll Search     Search Page [1]  
1/22/14 9:13am - Original Message: ''81 Secondary electric fan'
jimiam
Former Member
- Send Private Message


Memphis, TN - USA

Vette(s):
1981 Red 1993 Black Rose

Joined: 2/16/2007
Posts: 134
 Why do I have continuity between the two disconnected terminals on my '81 secondary fan motor? Should not one be a ground and one be hot? For whatever reason, I'm suddenly completely confused and lost here.
My understanding of the circuit is 12 volts from the fuse panel straight to the fan motor and a ground from the temp sensor to the fan motor which remains open until the sensor closes at x degrees completing the engine to ground circuit. What am I missing/overlooking here? It's as if the sensor opens and closes on a hot lead and the fan is grounded to the mount. But if that be the case how/why does the sensor ground to the engine? Heck all I know is I'm confused.  Confused 

____________________________________

(click to see a bigger image)
 Reply Reply  Quote Reply w/Quote
 
Support C3VR!
Suport our advertisers
1/22/14 12:27pm - Reply: 'Re: '81 Secondary electric fan'
Sarge81 Lifetime Member
Lifetime Member
- Send Private Message


WEST SENECA, NY - USA

Vette(s):
1981 Blue Ice Met. w/pearl ghost flames TKO500 5speed. LS1 Swap 3.45 Dana 44.

Joined: 12/3/2001
Posts: 2376
The fan switch in the cylinder head is the ground. The fan motor and mounting bracket is bolted to the fiberglass fan shroud. So there is no grounding there. 
That fan switch doesn't kick on until 238 degrees from the factory. Which in my opinion is way to hot to begin with. 

When I had my original aux fan in I used a temp switch from NAPA with the corresponding pigtail. That switch would come on at 204-220 degrees.  Part # ECH FS113. I don't have the corresponding part number right this moment. I'll look later on today.



____________________________________

GEN III 5.7L "LS6" Engine swap
TKO500 5 spd.
3.54 Dana 44
'69 "N11" Sidepipes
Borgeson Steering Box
Born 8/1981
Sequence #3975




Click here to see more pics of my Vette on CarDomain.


Lifetime Member #26
 Reply Reply  Quote Reply w/Quote
1/22/14 2:13pm - Reply: 'Re: '81 Secondary electric fan'
Adams' Apple Lifetime Member
Lifetime Member
Moderator
- Send Private Message


Duncanville, TX - USA

Vette(s):
#1-1974 L-48 4spd Cp Med Red Metallic/Black deluxe int w/AC/tilt/tele./p/w-p/b/ Am-Fm/map light National/Regional/Chapter NCRS "Top Flight" #2-1985 Bright Red/Carmine Cp.L-98/auto Member: NCRS, NCRS Texas, Corvette Legends of Texas

Joined: 11/8/2003
Posts: 19448
Are you measuring the FAN itself, or the connector on the car for the fan?
You're right in that the 12v power comes from the "Fan" fuse, and the temp switch in the cylinder head provides the ground when it gets to it's pre-set temp rating...assuming the switch is functional. Have you disconnected the temp switch and checked the resistance on the connector then? If you disconnect the temp switch, and STILL see continuity between the two wires in the connector, you probably have a short between the two somewhere. If you do NOT have continuity with the switch disconnected, the switch itself may be gummed/corroded internally, causing the resistance. Check the switch itself....you should have NO continuity between the terminal and the switch body/ground. If you do, the switch needs to be replaced.


btw...if you have continuity on the ground side, the fan should be running all the time, depending on how solid the short is. Sometimes, the temp sender wires get melted on the exhaust, and do silly stuff like this.....


|UPDATED|1/22/2014 11:13:29 AM (AZT)|/UPDATED|


____________________________________
Joel Adams
C3VR Lifetime Member #56    
My Link


(click for Texas-sized view!)
             NCRS

"Money can't buy happiness -- but somehow it's more comforting to cry in a CORVETTE than in a Kia"
 Reply Reply  Quote Reply w/Quote
1/22/14 5:38pm - Reply: 'Re: '81 Secondary electric fan'
jimiam
Former Member
- Send Private Message


Memphis, TN - USA

Vette(s):
1981 Red 1993 Black Rose

Joined: 2/16/2007
Posts: 134
With no wire connected at the switch there is no continuity between either of the two terminals to switch housing, nor between the two terminals. Should there be two terminals on this switch or one?
Measuring at the fan terminals there is continuity with no wires connected. From the fan terminals there are two wires which run to a 2 pin connector located above and front of the fender near the a/c compressor. Disconnected at the fan terminals, there is no continuity between those two wires. From that connector's mate, a black wire runs directly to the fuse panel. A light blue wire runs to a six pin connector near the fire wall where it mates to another wire running to the temp switch.  With everything connected, because of the continuity between the terminals at the fan both the light blue and the black wire show 12 volts when grounded back to the chasis via the multi meter or a test light and the fan is not running. With all wires disconnected at the fan, I can run a 12v wire to one of it's terminals and a ground to the other and it will run.  I'm probably not doing a good job describing this, but it's the best I can.

____________________________________

(click to see a bigger image)
 Reply Reply  Quote Reply w/Quote
1/22/14 5:48pm - Reply: 'Re: '81 Secondary electric fan'
jimiam
Former Member
- Send Private Message


Memphis, TN - USA

Vette(s):
1981 Red 1993 Black Rose

Joined: 2/16/2007
Posts: 134
Sarge81 said: The fan switch in the cylinder head is the ground. The fan motor and mounting bracket is bolted to the fiberglass fan shroud. So there is no grounding there. 
That fan switch doesn't kick on until 238 degrees from the factory. Which in my opinion is way to hot to begin with. 

When I had my original aux fan in I used a temp switch from NAPA with the corresponding pigtail. That switch would come on at 204-220 degrees.  Part # ECH FS113. I don't have the corresponding part number right this moment. I'll look later on today.



Thanks sarge. I agree 238 degrees seems much too late for that fan to kick in. Though I've heard many folks say these things run better a little on the warm side. I couldn't say as I very seldom see mine below 200 on the gauge.


____________________________________

(click to see a bigger image)
 Reply Reply  Quote Reply w/Quote
1/23/14 2:12pm - Reply: 'Re: '81 Secondary electric fan'
Adams' Apple Lifetime Member
Lifetime Member
Moderator
- Send Private Message


Duncanville, TX - USA

Vette(s):
#1-1974 L-48 4spd Cp Med Red Metallic/Black deluxe int w/AC/tilt/tele./p/w-p/b/ Am-Fm/map light National/Regional/Chapter NCRS "Top Flight" #2-1985 Bright Red/Carmine Cp.L-98/auto Member: NCRS, NCRS Texas, Corvette Legends of Texas

Joined: 11/8/2003
Posts: 19448
The two terminals ON the fan itself should have continuity(with the connector un-plugged)...those are the windings of the fan motor. You're good there.
The fan switch should only have ONE terminal. Another temp sender with two terminals is for the gauge/ECM input.
With the system connected, you WILL show voltage(key on) on BOTH wires(at the fan motor) until the fan/temp switch closes, and gives you a ground.

With the key ON, take the connector loose from the fan temp switch, and run the wire from the connector to ground....the fan should run. If it does, the wiring is all good. Then, if the fan is not coming on when the engine gets hot enough for it to be needed, the temp switch is no good. As Sarge mentioned, you can get another switch with a lower closing calibration that will kick the fan on sooner. Thumbs Up

____________________________________
Joel Adams
C3VR Lifetime Member #56    
My Link


(click for Texas-sized view!)
             NCRS

"Money can't buy happiness -- but somehow it's more comforting to cry in a CORVETTE than in a Kia"
 Reply Reply  Quote Reply w/Quote
1/23/14 2:20pm - Reply: 'Re: '81 Secondary electric fan'
rraider1
Former Member
- Send Private Message


Woodland, WA - USA

Vette(s):
1977 T-Top,350,Auto Black Ruby Pearl,Steeroids R&P conversion

Joined: 10/14/2003
Posts: 1152

 

http://content.mamotorworksmedia.com/production/website/articlefiles/installfiles/601972_X.pdf

 

It looks like replacement switches have 2 wires. This is from Mid America.

If you are going to put a meter on the 2 wires coming from car to fan you would have to remove the fuse and disconnect the temp switch to isolate the circuit. to check to see if there is continuity between them or a short to ground. If their was a short to ground on the pink wire the fuse would blow if the lt blu was shorted to ground fan would run all the time, if the wires are shorted together and the temp switch closed it would burn out the contacts in the sw.

This is how I would check it.

Disc the connector to fan, disconnect connector at temp sw check for continuity between the 2 wires at the fan Con car side if shorted together (bad) look for wires melted together. Ground the lt blu wire at temp sw , now check for 12v pink wire at fan Con. If not this is the circuit that is bad and you can concentrate here. If OK check for ground on lt blue wire at fan connector. If no ground this is the circuit to follow.

 

Now what is not clear is the temp sw. if it is a 1 wire it would ground threw the sw to the block. (if it was wrapped with Teflon tape could effect that)The MA instructions say to hookup just the lt blue wire to existing lt blue, which would indicate it grounds through the sw to block. But the 81 wire diagram shows that the temp the sw makes and grounds through the sw black wire to ground  



____________________________________
Bob R
 Reply Reply  Quote Reply w/Quote
1/24/14 10:23am - Reply: 'Re: '81 Secondary electric fan'
jimiam
Former Member
- Send Private Message


Memphis, TN - USA

Vette(s):
1981 Red 1993 Black Rose

Joined: 2/16/2007
Posts: 134
Picked up a new sensor with a lower temp setting and with the info from you guys the fan seems to be working great now. Reading voltage on both those leads was really confusing me. I don't know if it's an age thing or what, but a lot of fundamentals seem to evade me in recent months. Oh well, with you guys here to bail me out I'm good as long as I can remember how to log on.
Thanks again for all the help. I appreciate your knowledge. Clap





|UPDATED|1/24/2014 7:23:00 AM (AZT)|/UPDATED|


____________________________________

(click to see a bigger image)
 Reply Reply  Quote Reply w/Quote
1/24/14 2:01pm - Reply: 'Re: '81 Secondary electric fan'
Adams' Apple Lifetime Member
Lifetime Member
Moderator
- Send Private Message


Duncanville, TX - USA

Vette(s):
#1-1974 L-48 4spd Cp Med Red Metallic/Black deluxe int w/AC/tilt/tele./p/w-p/b/ Am-Fm/map light National/Regional/Chapter NCRS "Top Flight" #2-1985 Bright Red/Carmine Cp.L-98/auto Member: NCRS, NCRS Texas, Corvette Legends of Texas

Joined: 11/8/2003
Posts: 19448
 Clap Thumbs Up

Glad ya got it fixed!
'Lectrical stuff can be confusing as heck at times. But....just remember that a MOTOR will show voltage on both sides of the connection until it gets switched to ground. Light sockets are the same way....until the circuit goes to ground, there is voltage on both sides. That's where switches, and relays come into play. Thumbs Up


____________________________________
Joel Adams
C3VR Lifetime Member #56    
My Link


(click for Texas-sized view!)
             NCRS

"Money can't buy happiness -- but somehow it's more comforting to cry in a CORVETTE than in a Kia"
 Reply Reply  Quote Reply w/Quote
1/24/14 5:03pm - Reply: 'Re: '81 Secondary electric fan'
rraider1
Former Member
- Send Private Message


Woodland, WA - USA

Vette(s):
1977 T-Top,350,Auto Black Ruby Pearl,Steeroids R&P conversion

Joined: 10/14/2003
Posts: 1152
Glad you got it going

____________________________________
Bob R
 Reply Reply  Quote Reply w/Quote
1/24/14 5:15pm - Reply: 'Re: '81 Secondary electric fan'
jimiam
Former Member
- Send Private Message


Memphis, TN - USA

Vette(s):
1981 Red 1993 Black Rose

Joined: 2/16/2007
Posts: 134
Adams' Apple said:  Clap Thumbs Up

Glad ya got it fixed!
.............


Well Joel, Bob, sarge, ya gotta admit, it's usually pretty easy to fix stuff when somebody tells ya how. C3VR, my desktop mechanic. Thumbs Up






|UPDATED|1/24/2014 2:15:25 PM (AZT)|/UPDATED|


____________________________________

(click to see a bigger image)
 Reply Reply  Quote Reply w/Quote
1/24/14 5:35pm - Reply: 'Re: '81 Secondary electric fan'
rraider1
Former Member
- Send Private Message


Woodland, WA - USA

Vette(s):
1977 T-Top,350,Auto Black Ruby Pearl,Steeroids R&P conversion

Joined: 10/14/2003
Posts: 1152
Hey at least my knuckles did not get scraped up, I'm learning its easier to tell someone else how to do something than do it yourself 

____________________________________
Bob R
 Reply Reply  Quote Reply w/Quote
1/25/14 6:38am - Reply: 'Re: '81 Secondary electric fan'
Sarge81 Lifetime Member
Lifetime Member
- Send Private Message


WEST SENECA, NY - USA

Vette(s):
1981 Blue Ice Met. w/pearl ghost flames TKO500 5speed. LS1 Swap 3.45 Dana 44.

Joined: 12/3/2001
Posts: 2376
Cool man! Glad you have it sorted out. Thumbs Up

Sorry I didn't get back with you sooner with that part number for the pigtail. We've been busy at work with snow removal stuff. 


____________________________________

GEN III 5.7L "LS6" Engine swap
TKO500 5 spd.
3.54 Dana 44
'69 "N11" Sidepipes
Borgeson Steering Box
Born 8/1981
Sequence #3975




Click here to see more pics of my Vette on CarDomain.


Lifetime Member #26
 Reply Reply  Quote Reply w/Quote
 New Topic New Topic Post Reply Reply New Poll New Poll Search     Search Page [1]  
 Forums -> C3 Electrical
(Moderator: Adam Wartell, Norsky, Adams' Apple)
 

 
Official C3 Vette Registry Community:
Home | Forums | Email | Who's Online | Clubs | Events | Member Stats

Other Official C3 Vette Registry Areas:
Members | Research | Shop | My Account | About C3VR
 

Corvette is a registered trademark of the General Motors Corporation(GM) & Chevrolet Motor Division. Vette Registries, LLC is responsible for all site content (except for member submitted content or where otherwise noted) and does not claim or imply that Chevrolet or GM is responsible for Official C3 Vette Registry content. Vette Registries, LLC is independent from GM and is not affiliated with, sponsored or supported by GM.  Copyright/trademark/sales mark infringements are not intended, or implied and are in fact used to support GM, Chevrolet and Corvette

Official C3 Vette Registry content is Copyright 2001-2017, Vette Registries, LLC. Content may not be reused without written consent. All Rights Reserved. NS

Corvette (Vette) Model Years on this site: 1968 1969 1970 1971 1972 1973 1974 1975 1976 1977 1978 1979 1980 1981 1982 30