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fan may or maynot run

871 views 13 replies 6 participants last post by  S10xGN 
#1 ·
My fan has a problem. Sometimes it may run or stop running. If I cycle the switch it may run or not. When it stops running there is no power to pin number 87 which is the fan wire. There is still power to 30 and 85 and ground to 86 (may have that backwards). The voltage at 85 will be around 2.67 volts.
 

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#3 ·
Was it working OK but now it's not?
The normal setup is like this:
Power to relay #85 must be hot when the ignition is on. This is first place to check.
Connect a test light to #85 and ground to test this idea.

vicrod
It was working ok. The voltage at #85 will be around 2.67 volts when the fan quits and there is no power at 87 which is the fan wire.
 
#4 ·
That low voltage on #85 is the problem but why?
The reason I like using a test light is that puts a load on the circuit under test.
This is good example of a feedback problem that is giving you the odd voltage.
The wiring that feeds the relay #85 must be checked for good connections.
I'm assuming the control is on the ground side of the relay #86.

vicrod
 
#9 ·
use a test light

It seems that the 12 volt source for the relay coil is the problem.

An easy test would be to connect a temporary jumper from the battery to the relay coil. This will rule out the relay and the relay coil ground.
Then you need to find the issue with the ignition sourced feed to the relay.
Check the relay socket.

FWIW- Whenever I do troubles like this I use a test light. The actual voltage is not the issue. Poor connections will show up when a load is present. Meters do not load the circuit.

vicrod
 
#11 ·
It seems that the 12 volt source for the relay coil is the problem.

An easy test would be to connect a temporary jumper from the battery to the relay coil. This will rule out the relay and the relay coil ground.
Then you need to find the issue with the ignition sourced feed to the relay.
Check the relay socket.

FWIW- Whenever I do troubles like this I use a test light. The actual voltage is not the issue. Poor connections will show up when a load is present. Meters do not load the circuit.

vicrod
I disconnected the power lead to pin 85 (the rocker switch) and jumped it from pin 30 to 85. Ran the fan for 25 minutes without failure. Started and ran car for 30 minutes wired this way with no failure. Thinking it's in the dash wiring. Oh Joy!
 
#13 ·
Check the output at the ign. switch ....if it's an aftermarket switch , my 1st one only lasted a couple mo. , next 1 has been working fine for the last 14 years....same switch, same company..
dave[/QUOTE

Same wire that runs the fuel pump switch also runs the fan switch. Voltage at both switches is battery voltage. fuel pump works fine. Rocker switch relay wire is at 2.57 for the fuel pump relay pin 86 and the fan relay voltage is at 2.68 but the fan won't run but only a few minutes until it may or may not stop running. and all voltages remain the same except for no voltage at pin 87.
 
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