Hi guys!
i wired 2 manual switches on the 2 relays of my 2 radiator fans and added 2 lights on the dash that tell me when the fan/fans is/are on.

Here's what i found on my 88 IROC-Z 350 TPI:
- if i turn the key without starting the engine i can manually start both (together or one by one) the 2 fans.. so everithing as aspected.
- with the engine running if i start the driverside fan, it starts.. everything ok.
- with the engine running if i start the passengerside fan, it starts.. and automaticaly the other fan starts and stops only if i speed up to 30 mph.. if i pull over it starts again.

This strange thing appens with the engine running only.

Is this normal?

thank you all!

ciao
Manu

[QUOTE=asfalto;4519876]
.. and automaticaly the other fan starts and stops only if i speed up to 30 mph.. if i pull over it starts again./QUOTE]

The primary fan, ECM switched (stock controlled), will turn off around 30-35mph. The airflow through the radiator at that speed, and above. makes the fan running, mostly useless.

Short answer, yes, it is normal.

yeah, that's true.
but the strange thing is that the ECM fan starts when i manually turn the other fan on.. with the engine on.
if the engine is off everything is regular!

thanks for the replay!

ciao

Since you are grounding the passenger (secondary), you may be (inadvertently) sending an 'a/c request' to the ECM which cause both fans to run (the ECM fan will still shut off at speed, though).
I don't have diagrams handy at the moment not in the house) but, 88 or 89 (I think 88) changed how the dual fans operated (with the A/C).

Everything sounds good to me. With just a 200/185 switch in the passenger cylinder head and the A/C off, both my fans will come on at 200. I'm using the stock ECM right now which "should" turn the primary fan on at 223°. But the secondary fan seems to override the primary one, causing both to come on at 200°.

Your car sounds normal.

very good!
now that i now everything is normal i'm very glad to enjoy this new useful feature of my cooling system!

many thanks!!!

ciao
Manuel

also read other important informations from your replies on thread "Secondary Fan doesnt turn on" by TheJoeY88 !

thank you!