Car cutting out when thermo kicks in

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I seem to have a strange problem, and need some opinions on the issue.

I have my microtech (LT8S) re-wired when i had to re-wire the rest of my car. All is well and good until i struck a problem in traffic, when my water temp creeps upto 94degrees, and my thermo kicks in. The car stumbles and stalls.

After a quick look around, the autoelec has taken the power all from my ignition switch, so i have the ecu, pumps, and fans all on the same line. From looking at the microtech when this stalling happens, the voltage drops hardcore to around 5V until the engine/alternator can catch up. (some revs are required to stop it falling over completely)

Would it be to my advantage to take all these accesories off the same line, and route them to different points? Like have my ECU take the power straight from the starter, and leave the pumps and fan on the ignition switch? Or should i go further, and take all the power from the starter?

Other information, with the engine off, and the ignition on, the voltage read by the microtech is 12.36 with the pumps disconnected, and drops to 11.9 when the pumps are activated. I assume that it would drop further if the fan was on at the same time as well.

When the engine is switch on, and only the pumps and the ecu running, i show 13.6 volts on the microtech. And when the fan kicks in, and after i restart it (after the stumble) it reads around 12.6V.

I assume the large current inrush into the fan when it is strating is sapping all the current out of the line, and temporailly takes power away from my pumps and ecu.

so... hrrrm?

Any insight would be great, as it is very furstrating having the car stall intraffic.

[takai]

The thermofan should be run through a relay straight off the battery, that way the current draw on the line to the ECU is minimal

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The thermofan should be run through a relay straight off the battery, that way the current draw on the line to the ECU is minimal

Ah ok, well thats a job to be done on the weekend.
Would it be worthwhile moving all of them directly to the battery/starter though?

[Granto]

Yeah, hookup a relay for the fan, then think about giving your autoelec a swift kick to the head! wtf.

Grant.

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Yeah, hookup a relay for the fan, then think about giving your autoelec a swift kick to the head! wtf.

Grant.

The fan is already on a relay. Just taking the battery source from the white wire at the ignition.... Along with everything else lol

[takai]

Pumps i would run off the battery via a relay too, ECU would be fine off the IGN.

[Granto]

Oh okay, that's easy then, just a matter of running some line from the battery to the relay.

Sorry was imagining he had it powered off the ECU! That'd be terrible for the life of the ECU.

Grant.

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Ok, so just to check

ECU off the ignition
Pumps+Fan off the battery.

Done and done, a simple wuick re-wire job. Many thanks +rep to both.

[jonra23]

All relays should run power direct from battery/starter/ Altenator, otherwise kind of defeats the purpose of having relays.

regards
jon

[takai]

All relays should run power direct from battery/starter/ Altenator, otherwise kind of defeats the purpose of having relays.

regards
jon

QFT, thats why relays were invented.

[thechuckster]

and those power supply lines should all be fused ahead of the relay.

[jonra23]

An autoelec wired it this way?
You take it to a tradesman to get it done right, then you fix it.

regards
jon

[thechuckster]

An autoelec wired it this way?
You take it to a tradesman to get it completely arsed up, then you fix it.

fixhored...

[-==L=a=N=c=E==-]

An autoelec wired it this way?
You take it to a tradesman to get it done right, then you fix it.

regards
jon

I asked him that when i was looking at the wiring, and assured me it wouldn't be an issue. And it didn't have any issues while the car was sitting still idling with the fan on. It was only when i started driving that the issues started coming up.

I'll be damned if im chasing him up to fix it. Took them 5 months to get my car runnin...

So yeah..

[takai]

The IGN feed wire wouldnt be much more than 30A, so he wouldnt have needed to fuse it there due to little change in max current draw. However, definately fuse them off the battery.
Infact, buy one of these: http://www.narva.com.au/Fuses_Boxes.html and use that. I have a little 4 block in my car. easy as to fab up a little plate to mount it off. I just mount my plate off the battery hold down strap using a piece of 2mm alloy.

Ill post a pic tomorrow so people understand what im talking about. This is the one in my race car though: