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#1 |
![]() Join Date: Jan 2012
Location: Houston, Texas
Posts: 17
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1990 #849 black/black--Houston,Tx- I have searched through previous posts, and looked through the solutions section and haven't found this problem discussed. About two weeks ago I went to start the zr-1 the battery was very, very low. (The battery is less than 6 months old-Auto zone black and yellow battery) Charged battery about 24 hours,battery took a full charge- car started like it normally does. As soon as the engine started both radiator fans came on (they do not come on when the key is on, only with the engine running. Went on a short drive (about 5 miles) hoping the fans would return to their normal state-they didn't. Checked for ccm codes (wire between A&g)no codes were displayed in the speedo area. I then checked the ac codes-none there.Checked the ecm codes (wire between A&B)Flashed 12 over and over. Pulled the connector and jumped the connector of the a/c high pressure switch fans still ran.I have disconnected the battery hoping something would reset- no help. Pulled the fuse for the ecm( I think) put it back in fans still run. Took one of the relays apart it was not stuck closed, no corrosion inside. Today I hooked up an Actron CP9145 no codes present. went to the view data section- I noticed a few thing I am not sure about the scanner says open loop,it had a section that said En freon--Yes was displayed to the right of that- not sure what that means. The one that stood out the most was oil temp it displayed 265- would that make the fans come on? (The oil was'nt hot the dash gauge had barely moved, car had been idling about two minutes) If anyone can offer any suggestions on what I should do next, they would be greatly appreciated. The car has about 63000 miles and has run perfectly the past 15 months. Thanks in advance epaul77055
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#2 |
![]() Join Date: Jan 2009
Location: Portland Oregon metro area (Washington side)
Posts: 3,207
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The coolant fans are operated by two separate relays
therefore I'd say they are being told to go on by the ECM. When you pull either relay only one fans runs? Are you absolutely sure BOTH are coming on? And you say as soon as you start the engine? The ECM uses three inputs for control. VSS (speed) Water temp A/C High pressure side.
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Scott ![]() Vett owner since 1979._It's about the car and the people |
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#3 |
![]() Join Date: Jan 2012
Location: Houston, Texas
Posts: 17
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Yeah, I am positive both fans are running, you can unplug the relay on either one and the fan stops. You can switch the relays and they do the same thing.Just looked at it again took it for a drive --Car runs well normal start,good idle,secondaries working- water temp ok, oil temp ok according to dash gauges. Connected scanner to check temps-scanner and gauges were very close.
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#4 |
![]() Join Date: Jan 2009
Location: Portland Oregon metro area (Washington side)
Posts: 3,207
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I think you're going to have to do an investigation of the oil temp sensor and connector. The circuit description does not say the ECM looks at oil. It only says water but maybe that is incorrect
What does you data scanner say the water temp is?.
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Scott ![]() Vett owner since 1979._It's about the car and the people Last edited by scottfab; 11-05-2012 at 09:56 AM. |
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#5 | |
![]() Join Date: Feb 2006
Location: San Antonio area
Posts: 1,179
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Good luck ...
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“Buy the best example of what you want, and pay whatever it takes. That way, you cry only once.” ~ Bruce Meyer |
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#6 |
![]() Join Date: Jan 2009
Location: Portland Oregon metro area (Washington side)
Posts: 3,207
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Easy enough to test the theory of oil temp.
Just pull the connector and see if the fans stop.
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Scott ![]() Vett owner since 1979._It's about the car and the people |
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#7 |
![]() Join Date: Jan 2012
Location: Houston, Texas
Posts: 17
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Update: Finally figured it was the A/C requesting the fans. Replaced the A/C Fan pressure switch(the one on the small line closest to the firewall--Took less than 5 minutes) Fans are working properly. Thanks for everybody's input.
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#8 | |
![]() ![]() Join Date: Nov 2007
Location: Squires (near Ava MO in the Mark Twain N'tl Forest) - Missouri
Posts: 6,493
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P.
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Good carz, good food, good friendz = the best of timez! 90 #1202 "FBI" top end ported & relieved Cam timing by "Pete the Greek" Sans secondaries Chip & dyno tuning by Haibeck Automotive SW headers, X-pipe, MF muffs Former Secretary, ZR-1 Net Registry |
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#9 |
Join Date: Feb 2017
Location: Southbury CT
Posts: 101
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I fogot the GM ac deal. Is there a shrader valve behind the switch?
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#10 |
![]() Join Date: Jan 2012
Location: Houston, Texas
Posts: 17
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yes there is a Schrader valve-very little Freon was lost when putting on the new part. A very short hiss when taking old part off.
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