Radiator fan will not come on - AC works, ECTS good, Fan motor works

[afskwarek]

Hi all,

Been having an issue with my radiator fan not coming on on my 1999 SL1. Since summer has arrived and the reality of stop and go traffic in 100F weather is coming close, I figured I should fix it. Here's the thing though. I'm pretty stumped on what it is.

So here's what I've done so far, AC works and is at proper pressure, fan will not come on when AC is activated. I tested the fan motor via a direct 12v connection to battery. It comes on and works fine. ECTS was replaced about 30k miles ago with the good model. Did the test anyways of unplugging it, and also used a paper clip on the ECTS connector to check it. Fan did not come on either way. Swapped the fan fuse from a different Saturn with a known working fan, still did not come on. Pretty sure it's not getting power for whatever reason.

Really not sure what to do next at this point. Anyone have any pointers?

Thanks

[Waiex191]

Try swapping the fan relay.

[afskwarek]

Sorry, I was getting fuse/relay mixed up again. But yeah I did that with several different relays as well as the 30a fuse, still no dice.

[fetchitfido]

Next thing to try is jumping pin 87 to pin 30 of the radiator fan relay connector in the fuse box.
Use a 14awg wire and clean off about 1in of the sheathe off each end, then just shove it in the pins (IPA makes a kit for $45ish, seems silly just for testing).
If it turns on the fan (key off) then power is fine to the fan from the battery & fusebox so it has to be an issue with the activation circuit (pins 85 and 86).

[afskwarek]

So I did try to jump pins #30 and #87. Fan still won't turn on. Had a tone circuit tracer lying around figure Id give it a try. Connected it to the fan connector. Got good tone on the fan connector wire up to where it goes into the harness bundle. Also got solid tone on the fan relay, so the wiring from the connector to relay must be good unless I'm doing something wrong which is totally possible. Quite perplexed at this point.

[billr]

Do you have 12V at either #30 or #87 of the relay socket?

[afskwarek]

Yes. I'm getting voltage at one of those pins. I know which two pins are either 30 or 87 (lower left and upper right). However since the relay can go in two different ways, I'm not sure which one is which. Let me guess, due to orientation of the fuses #30 is upper right? I'm probably wrong. Wouldn't be surprised. Anyways, didn't detect any voltage from the lower left pin.

I'm also getting voltage at the lower right pin, and a tiny amount on the upper left pin. Don't know if that's relevant or not.

https://ibb.co/HqY8KNb

https://ibb.co/FVMR368

https://ibb.co/kc48N7X

[billr]

You are using the meter wrong. One probe lead always goes in the "COM" jack.

[afskwarek]

Thanks. When it comes to electrical I don't trust myself at all so I'm glad I took photos. So which probes should I plug into what jack?

[billr]

One lead always goes in the "COM" jack. In most cases the other lead goes in the "V*mA" jack, with * meaning the "omega" symbol for ohms. The only time the upper jack ("10ADC") is used is when the rotary selector is set for "10A" and you are wanting to measure DC currents greater than 200mA. Note that all other ranges are rather forgiving if you reading range is exceeded. That 10A range is not! You may dramatically damage that function, complete with smoke and burning smell, if you connect to a circuit that can supply much more than 10A.

PS: color of which lead goes in which jack is irrelevant, but most of us use the black lead in the COM jack.

[afskwarek]

Got it. Thanks for clearing that up for me. Something didn't seem right. Anyways, sorted that out and I'm getting voltage in the two right side pins.

https://ibb.co/B3nZwtt

https://ibb.co/Fbn24s4

[billr]

Those latest pix won't open for me, but check for 12V at the wire that connects to the compressor, with the wire still connected to the compressor.

"Got good tone on the fan connector wire up to where it goes into the harness bundle."
It isn't clear to me that the whole relay-to-compressor wire was checked by that. Right under the relay socket there is another connection on each wire. All the relay/fuse sockets are "double-ended" females, with the wire harnesses plugging in underneath the UHJB.

[afskwarek]

Alright. So my apologies for being so green. But with the ac compressor connector plugged in, where exactly do I check that wire for voltage? Sorry for my confusion. I checked the hvac wiring schematic and it looks like that wire goes straight to the relay so Im not sure how/where to check it.

[fetchitfido]

Well, you've verified that both sections of the relay are receiving power, now you need to verify both sections are getting ground. The relay should have pin numbers written on it, very tiny & hard to see but they're there. 85 and 30 should have power, when the fan is activated 86 should have ground and 87 goes to the positive terminal on the radiator fan plug.
I might have 85 & 86 mixed up, just verify one has power and one has ground when the radiator fan is expected to be on.

[afskwarek]

Alright. So I turned on the AC and got no voltage on lower left pin 87, and 0.03v on the upper left pin 86. Out of curiosity I jumped 30 and 87 and got good voltage on the jumper wire. Should I be using a different setting on my multimeter?

https://ibb.co/PQp4nmt
https://ibb.co/NWQrWxt

[billr]

The meter set-up is fine, but is that how you are connecting the black lead; just shoving it in between painted fender parts??? Connect that black/COM lead to a good ground, like the battery negative terminal or engine block/head.

[afskwarek]

Okay thanks. Yeah that was so I could snap photos. I did put the com probe to negative battery terminal as well as body beforehand the readings were the same.

[fetchitfido]

Pin 30 has a direct connection to the battery. Pin 87 has a direct connection to the radiator fan. The only time 87 should have power on it is when you jump it from 30 or the relay is installed and turned on. If the fan isn't running with this pin jumped then you need to do a connectivity check between 87 and the power pin on the fan connector. If that is connected, do the same with the ground wire; if that's also good the issue is the fan motor but you can give it power & ground bypassing the car wiring if you want to be sure before replacing it.

Pins 85 and 86 turn the circuit "on" which tells the relay to jump power from 30 to 87. One should have the same battery power reading as the battery and the other is the ground that the PCM turns "on" (floating/unconnected when off, solid ground when on). If the floating ground doesn't turn solid when the fan is expected to be running, you have to test it from the pin to the PCM to find where it's broken. I can track down the pinout & wire color tonight, though I'm sure its been posted before.

[billr]

The OP already applied 12V directly to the fan connector, and the fan worked OK. It is unlikely either the fan motor or the motor ground are bad.

It is time to answer the question about how to back-probe...

Simply slip a skinny "probe extender" alongside the wire entering the back (wire-side) of the harness connector; very similar to using the paper-clip at the fuse/relay panel. Sewing needles or hat-pins work great for this, you can also use them to simply pierce the wire insulation just outside of the connector.

The whole idea is to get a voltage reading at that wire powering the fan, with the wire connected to the fan so there is some appreciable current draw on the circuit. If you check for voltage with no load, a "good" reading is inconclusive. Same for the continuity buzzer. it can tell if the circuit is definitely bad, but not prove that it is good.

[afskwarek]

Alright this is what I got. I used a hairpin, ground off the ends to get exposed metal, bent it, slipped it in the connector and plugged it in a spare fan motor (motor has been tested and works). Got a consistent 12-14 volts at the fan connector. Fan motor didn't turn on.

https://ibb.co/3h926RY

https://ibb.co/JzGXZ8c

https://ibb.co/WBjCJWG