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1991 Chevrolet Lumina OBD port.

Tiny
MIKE LUCKEY
  • MEMBER
  • 1991 CHEVROLET LUMINA
  • 3.1L
  • 6 CYL
  • FWD
  • AUTOMATIC
  • 161,000 MILES
Why do the cooling fans come on when I paper clip jumper A and B to read my obd1 engine codes? Thank you in advance.
Wednesday, March 4th, 2015 AT 8:30 AM

6 Replies

Tiny
HMAC300
  • MECHANIC
  • 48,601 POSTS
It's been so long since I checked one I think it is designed to do that.
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Wednesday, March 4th, 2015 AT 9:29 AM
Tiny
MIKE LUCKEY
  • MEMBER
  • 38 POSTS
I thought that was probably the case. Having a bit of trouble with the fan not coming on. A/C doesn't work, so the secondary fan probably won't, but the primary fan should. I replaced the ECT and the relay. I took the connector wire off of the ect and jumperwired it and thought that would work, no dice. So I jumper wired in the relay socket from the always hot pin to the load (fan) pin and the fan came on! Could I have a problem between the ect and the relay?
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Wednesday, March 4th, 2015 AT 2:15 PM
Tiny
HMAC300
  • MECHANIC
  • 48,601 POSTS
It may be a problem with the fuse box. Check relay to see if you get any power to it if you do twist or bend the prongs a tad and see if it works that way. It may be making poor contactor corrosion. I can't get into a manual to check circuit out so thatis all I can advise now.
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Wednesday, March 4th, 2015 AT 3:19 PM
Tiny
MIKE LUCKEY
  • MEMBER
  • 38 POSTS
Will do. Is there only one pin (#30) that has power all the time in the relay plug? Thank you again by the way!
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Wednesday, March 4th, 2015 AT 9:52 PM
Tiny
HMAC300
  • MECHANIC
  • 48,601 POSTS
When you key up onewill come from ect/pcm and the other will go out to fan. One is ground.
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Thursday, March 5th, 2015 AT 5:37 AM
Tiny
MIKE LUCKEY
  • MEMBER
  • 38 POSTS
Thank you!
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Thursday, March 5th, 2015 AT 6:35 AM

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