SpartanSV

That's bananas.

Got a link to the relays you're using? Did you use your clamp meter to take a current measurement before the relay?

sixshooter

iTrader: (12)

Yes, and it was very similar to the reading closer to the fan, to my recollection. There was some slight fluctuation while running so it would be tough to be exact, but I can try it out tomorrow.

Here's the relays:

SpartanSV

If the current measurement before and after the relay is similar then you can't have 151 ohms across the contacts.

I just measured a very similar relay at 0.2 Ohms across the contacts.

sixshooter

iTrader: (12)

I'll try a different multimeter tomorrow.

DNMakinson

iTrader: (3)

You my just not be using the meter properly. It sounds as if you are trying to read ohms across the contacts while the fan is on. That won't work. It is confusing the Multimeter.

The correct thing is to measure the amps, and then also measure the voltage drop across the contacts. Then you use Ohm's law to the resistance: Ohms = Voltage / Amperes

DNM

sixshooter

iTrader: (12)

You're right, I was touching 30 + 87 while the fan was engaged. I didn't realize that would make the difference to anything. For some reason I didn't think the meter was supposed to be bothered by things like that.

I just realized it was DNM and I put DKM earlier. My apologies. I certainly knew there was a K in it but it was in the middle of your last name.

Ted75zcar

iTrader: (2)

DMMs use a very small current source to create a voltage across the resisance being measured. If there is already a voltage there, it will muck the reading. I am glad to hear this is the reason for the reading you reported.

DNMakinson

iTrader: (3)

No worries. We’re just trying to get you to the Gap.

sixshooter

iTrader: (12)

Aha! I'll measure it with the contacts closed and the high current leads removed.

This is how the new wiring was done without a fuse holder. Thankfully it runs much cooler than the store bought holder.

sixshooter

iTrader: (12)

Why are you the only one who knew this, lol?

Bench testing the relay in the closed position with no high current leads attached yields an ohm reading of 0.1 to 0.0 on the same meter.

I'll try doing the voltage drop and amperage measurement method you described in a bit.

sixshooter

iTrader: (12)

25.1 amps inline

High current poles on relay during operation:
14.00v
14.02v

What does it all mean?

Ted75zcar

iTrader: (2)

Relay is fine

Edit: now measure voltage from relay output to fan input.

3 measurements
Relay out to chassis
Fan in the chassis
Relay out to fan in (mV scale)

All with fan running and associated current measurements

sixshooter

iTrader: (12)

Relay out to chassis 13.95
Fan in the chassis 13.85
Relay out to fan in (mV scale) 115.0mV
At 25.8 amps measured at fan input.

Ted75zcar

iTrader: (2)

Length of wire between relay and fan?

sixshooter

iTrader: (12)

18-24 inches I'm guessing. I'm on a run for parts right now.

Ted75zcar

iTrader: (2)

Pick up a 40A fuse while you are at it. The relay/wire situatuon sounds fine.

Do you have a thermocouple or an IR temp gauge?

sixshooter

iTrader: (12)

I have both. Thermocouple with multimeter was how I measured temperature earlier in thread.

Ted75zcar

iTrader: (2)

Great. Take temperatures of the components in question after heat soak, as well as other (preferably like materials/colors) surfaces in close proximity to the areas of interest.