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I have a 1968 Jeepster Commando sitting on a complete, mostly un-altered C5 chassis. Corvette body off, Jeepster body on. For space considerations, I moved my AC condenser to behind the motor requiring the addition of additional fans. Since I'm not using the Secondary Air Injection Pump I chose to use it's relay (#33) to drive the new condenser fans. I did so by tying the PCM ground signal going to Cooling Fan #1 (the wire going to Terminal E2 on Relay #45) to F9 on Relay 33.
As expected, the new condenser fans come on when Relay 45 closes either based on engine temp or AC system pressure. As not expected, the condenser fans and/or main fans turn on when I turn the ignition switch off. If I cycle the ignition switch on and off, the fans turn off.
I'm stumped. Any help would be appreciated.
It appears the coil of relay 45 has constant power and the coil of relay 33 has switched power so when you turn off the key you basically put the relay coils in series across battery power. The power goes through relay 45 to relay 33 and then from relay 33 to the other things powered from the same ignition switched circuit. The relays act odd because they are in series and only getting 1/2 power.
It appears the coil of relay 45 has constant power and the coil of relay 33 has switched power so when you turn off the key you basically put the relay coils in series across battery power. The power goes through relay 45 to relay 33 and then from relay 33 to the other things powered from the same ignition switched circuit. The relays act odd because they are in series and only getting 1/2 power.
I see what you mean. I totally missed that possibility when I decided to wire it this way. I don't know enough about electronics to know if adding a diode or something would fix the problem. What would you think about hooking E3 on Relay 45 to 85 on Relay 33 and grounding 86?
Thanks for your help.
When you spliced into relay 33, did you cut the wire from PCM terminal 36 and tape it aside? If you remove the terminal from relay 33 terminal 85 and splice to terminal 36, that should get things working properly. That removes potential grounds to the 33 coil relay when the ignition relay is open.
I see what you mean. I totally missed that possibility when I decided to wire it this way. I don't know enough about electronics to know if adding a diode or something would fix the problem. What would you think about hooking E3 on Relay 45 to 85 on Relay 33 and grounding 86?
Thanks for your help.
A diode spliced into the wire feeding Relay 33 terminal 85 with the band facing the relay would fix it.
The wiring you asked about will not fix it.
You can wire terminal 85 to 36 on relay 33 so both relay coils have power all the time.
You could also wire relay 33 terminal 85 to relay 45 terminal G3 so the relay coils are just connected in parallel.
I finally got back from a trip and had time today to resolve this issue. The plan was to tie the hot sides of both relays to +12V always hot. However when I took the under hood fuse/relay module apart to trace the circuit from the relay to proper wire I discovered that there are internal connections in the module precluding this option.
So I ended up adding an external relay with the =12 V side of the coil always hot and the problem is solved.
In case you don't know what the underside of the fuse/relay module looks like, here are a couple of images.
Removing one of three plugs from the back of the under hood fuse/relay module.
Underside of the fuse/relay module with all three plugs removed.
C5 fan issue
