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1997 Cadillac SLS engine overheating

Tiny
TINMAN268
  • MEMBER
  • 1997 CADILLAC SLS
  • V8
  • FWD
  • AUTOMATIC
  • 83,000 MILES
My 1997 cadillac sls 4.6L northstar has been overheating. I've replaced the t-stat, fan relays, flushed the system and refilled with the sealant pellets as required, and changed the ECT. Also as an HVAC service tech I've tested every circuit of the cooling system. Both fans are not coming on all the time when the a/c is running. Which leads me to believe a possible PCM problem. Such as not completing the circuit to make both fans run. They do run if the a/c is set to come on when the engine is first started, but when you turn the a/c off then back on only the driver's side fan runs. HELP! This is driving me crazy.
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Saturday, July 23rd, 2011 AT 11:21 PM

4 Replies

Tiny
RASMATAZ
  • MECHANIC
  • 75,992 POSTS
Reading it sounds like the PCM
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Saturday, July 23rd, 2011 AT 11:24 PM
Tiny
CADIEMAN
  • MECHANIC
  • 3,544 POSTS
Ck. The codes and troubleshoot by codes set.
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Sunday, July 24th, 2011 AT 1:06 AM
Tiny
TINMAN268
  • MEMBER
  • 3 POSTS
It's not throwing any codes codes other than an overtemp code. I am going to bypass the PCM with a switch circuit to allow the relay to switch the fan current.
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Sunday, July 24th, 2011 AT 2:31 PM
Tiny
CADIEMAN
  • MECHANIC
  • 3,544 POSTS
Are u receving power to the inop. Fan relay?
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Wednesday, August 8th, 2012 AT 1:55 AM

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