I did something stupid. Wayyyy back when I installed my Spal fan I ran both relays to it. The wires from Main Fan and Ad Fan were spliced together and went to the new fan. I had two relays so plenty of capacity, right? Until something happens. So stupid.

96 Miata, MS3 Basic

Up at Miatas at the Gap I noticed my radiator fan staying on. Here's what I found:
1. Ad Fan fuse blown
2. Main Fan relay melted and stuck in on position
3. Yellow +12v wire beneath the Main Fan relay melted to the blk/grn signal wire (ground from ECU). They were making direct contact.
4. Upon replacing Ad Fan fuse, compressor clutch engages when ignition key is turned to "run" position regardless of A/C switch or blower switch position. Even engaged with car not running. Verified relay (near passenger headlight) is good and is actually receiving ground signal to engage from ECU wire (blu/blk). Compressor clutch doesn't seem to disengage regardless of pressure switches

So I separated the melted yellow and blk/grn wires.
As a remedy I connected blk/grn (ECU ground signal for Main Fan) and blu/wht (ECU ground signal for condenser fan) together for them to signal a new 40amp relay for the Spal. High amp lead for the new relay comes from alternator +12v post with 30amp inline fuse.

I didn't see any other shorted wires yet during my inspection.

But I haven't cranked the car yet. I'm confused why the compressor clutch is engaged.

I disassembled the ECU case and saw no evidence of overheating or discoloration on any of the surfaces or components on the boards.

How do I test the ECU output to the compressor?
How do I test the ECU output to the fans? I guess I could run it awhile.
Did I smoke some components in the A/C part of the climate control unit?

Did I burn up part of the MS3Basic?

What did I do?

Many thanks.

Pics of wiring diagrams attached for reference.





@Joe Perez shuiend
Reverent
Braineak

 

It's pretty late at night over here to process this in a meaningfull way, let me put a notification so that I can check it tomorrow morning. Even better, send me a PM with a link to this thread just before you call it a night so that I can have a look tomorrow morning.

 

Oh, and my tach stopped working at the same time.

 

Damn, I almost wired my 14" Spal to both Fan Relays on my MSM. Figured one is probably good enough and wasn't sure about tieing both relays together. Thanks for clearing that up for me so I wouldn't change my mind later and use both relays. Hope there's no drastic damage!

 

Fan has too much draw for either of the stock relays. Needs an aftermarket relay rated for higher amperage and a dedicated set of wires.

 

I read 17amps on the box I think, sounds right for constant load?. Do you know what amperage you are pulling on start up and constant? Would triggering a dedicated relay from the oem relay be sufficient? I haven't ran mine so I haven't metered amperage. Do you know what the OEM relay is rated? Thanks

 

Short of the output stage to 12V, the output is gone. You will need to cut the black/green wire from the stock connectors going to the ECU, and connect it to one of the spare outputs on the rear DB-37 connector. By default, the fan is setup to use InjE, so connect it to any other free output (the ECU has 5 spare: Fidle, IAC1, Nitrous2, VVT, Boost) and configure the fan output in TS to use that output.

Tacho: The tacho signal runs under the circuit for the cooling fan at some point in the ECU, this means that the line may be either damaged by the heat of the power stage, or the line may be now short to the power stage itself. If the former happens, you may cut the tacho wire from the front of the ECU and just connect it to pin 10 of the DB37 connector (which is Tachout). If the latter happens, then you need to remove Q5 transistor (which is under the white MS3 daughterboard, just behind the yellow connector and about in the center of the ECU) and try again.

 

Where would I find a map of the locations of these outputs? My MS3 Basic was not acquired with a manual.

 

Email me your serial number.

 

I will email the serial in a minute.

I need to track down the cause of the engagement of the compressor clutch as well. Would the ECU be calling for that engagement or should I expect another harness wire short somewhere?

 

Fix the cooling fan output first, then the tacho, and we'll look at the a/c clutch last (in the ECU), just make sure all the wiring is ok before we start popping other outputs as well.

 

Email sent. For the record, serial number is 12513.

I will need to check the wiring going to the A/C headunit for melted wires tonight. So much fun. Everything is more difficult with a roll cage.

I see in the wiring diagram there are two grounds behind the dash for the fan switch. I vaguely recall one of them from when the dash was out. I will need to find them both and make sure they have good connections, among other things. Le sigh...