Using IAC1 for radiator fan control
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Read the manual to see if your question is answered there before posting. Many users will not reply if the answer is already available in the manual.
If your question is about troubleshooting, configuration, or tuning, you MUST include your processor type (MS-I or MS-II) and code version in your post. If your question is about PCB assembly or modifications, you must also include the main board version number (1.01, 2.2 or 3.0).
If you have questions about MS1/Extra or MS2/Extra code configuration or tuning, please post them at www.msextra.com Such questions posted here will be moved to: a temporary MSextra sub-forum, where they will be removed after 7 days
The full forum rules are here: Forum Rules, be sure to read them all regularly.
Using IAC1 for radiator fan control
I am configuring my MS to switch my radiator fan relay (ground switching mode) using IAC1. I am speculating that because the IAC outputs are rated to switch an idle air valve, that I do not need to use an interposing transistor to handle the relay coil current (about 35 mA). I am also speculating that because the IAC a and b outputs are complimentary (switch between ground and + 12 v), that when the fan switches off IAC1 will go to 12 v which should eliminate the need for a recirculation diode across the relay coil terminals, or would the addition of the recirculation diode be a good idea?
Re: Using IAC1 for radiator fan control
Never does any harm to fit a diode across an inductive load to prevent any spikes damaging the driver. Given they cost pennies.
Dave P, London UK.
Rover V-8
MSII V3
EDIS
Tech Edge Wideband
Rover V-8
MSII V3
EDIS
Tech Edge Wideband
Re: Using IAC1 for radiator fan control
I did a little checking after I found the part # for the IAC driver chip. The UDN2916LB full bridge motor driver chip used on MS2 already has internal fly-back / recirculation diodes so no external fly-back diode is required.