HELP ME FIGURE OUT INTERMITTENT FAN ISSUE

[grumpyvette]

HELP ME FIGURE OUT INTERMITTENT FAN ISSUE
LOOKING FOR IDEAS ON WHY MY 1996 CORVETTES FANS HAVE AN INTERMITTENT NO WORK PROBLEM, BECAUSE ITS INTERMITTENT ITS A p.i.t.a. TO ISOLATE, i,M OBVIOUSLY OVER LOOKING SOMETHING SIMPLE HERE!
yes IVE READ THRU THE SHOP MANUAL TEST FLOW SEVERAL TIMES, AND ITS LOOKING LIKE THE PCM
a logical step by step approach will lead you to the problem, youll be amazed at what youll learn reading links. use of a shop manual and multi meter can be very helpful

THE ONLY TROUBLE CODE IS p1641 (FAN RELAY DEFECTIVE)

COOLANT SENSORS HAVE BEEN REPLACED

HERES THE BASIC ISSUE

RELAYS r1,r2,AND r3 ARE new, AND HAVE BEEN REPLACED TWICE, THE RELAYS TEST GOOD AND THE SOCKETS THEY PLUG INTO TEST GOOD WITH A MULTI METER

THERES 14 VOLTS OF POWER ON LEADS A1,A2,A3,A4

THE FANS (F1 AND F2) ARE, AND HAVE BEEN REPEATEDLY TESTED AND WORK FLAWLESSLY IF CONNECTED DIRECTLY TO THE POWER
ground G117 TESTS GOOD

WHILE A GROUNDS ARE CONSISTENTLY MEASURING A BIT HIGHER OHMS THAN I CONSIDER IDEAL, WITH MY MULTI METER THEY MEASURE EXACTLY THE SAME AS SEVERAL OTHER C4 CORVETTE I,VE TESTED THAT HAVE ZERO ISSUES SO I DON,T THINK THATS THE ISSUE

http://garage.grumpysperformance.co...-air-conditioner-on-cooling.12232/#post-59597

viewtopic.php?f=32&t=3954&p=32913#p32913

 

[grumpyvette]

87vette81big posted this info

"Grumpy,

This the same 1996 Corvette LT-1 You have been working on with cooling fan issues?
Getting a haircut so my post will be short.
I assume the New correct 4 & 5 pin relays did not correct.
Single pole &double pole relays.

The electromagnetic coil windings in each relay is turned on by the ECM.
ECM provides a ground circuit path.
Coil winding on pulls the relay armature down , contacts close.
Cooling fans supplied +12 vdc.

Need to check ECM Connector C1. Terminals #10 & 11.
Do a continuity resistance check back to pins # 86 of relays #1, 2 &3 respective following schematic provided.

Any more than .2 ohms or 2 tenths of an Ohm resistance is Unacceptable.
Also check ECM grounds.
At least 2 grounds on any ECM.
REDUNDANT GROUNDS. BACKUP.
GM TYPICAL USES 4 GROUNDS TO ECM DIRECT.
FULL ECM TERMINAL SHEMATIC NOT SHOWN.
BE TRANSLUCENT BLUE, RED, GRAY & BLACK ECM CONNECTORD ON 1996 VETTE.

You can remove ECM, SET ASIDE.
RECONNECT BATTERY.
MAKE A DEDICATED JUMPER LEAD.
PROVIDE RELAY GROUND FROM NEGATIVE BATTERY POST TERMINAL.
IF ALL WELL FANS WILL STAY POWERED UP NEXT HALF HOUR & NEVER STOP.
JUMPER TO ECM CONNECTOR C1 , # 10 & 11 TERMINALS.

DYNAMIC LOAD TESTING I CALL IT."