So here is what I have. I noticed yesterday after sitting for a bit my A/C was coming out warm.(A/C is cool while driving.) So my fans aren't coming on with the A/C like they should be. While poking around under the hood my coolant overflow started boiling/bubbling from the engine getting to hot. So I shut it down and let it cool. Checking things as I waited. After about 5 min. I started it up and the fans worked.

Anyway they stopped working again with the A/C on not sure how they fixed themselves the first time. When I unplug the sensor at the bottom of the radiator my fans don't come on like they should. When I turn on the A/C the fans don't come on but the A/C unit does start to cycle the clutch engages and there is bubbles in the site glass where the pressure switch is.

I replaced a sticking pressure switch last year because the fans were staying on. Could a bad pressure switch be causing the fans not to work at all? I checked all my relays and fuses and they seem fine.

It actually sounds like two different problems: first, the cooling fans should come on once the temp reaches spec (approx 200°F). Secondly, when the HVAC is switched on, the condenser fan should cycle on but you say neither is coming on at times.
That sounds to me like a failing/sticking relay but the key to this will be testing while in failure mode so you can check power feeds to the fans and see what is missing.
A non-powered test light will work but a logic probe used properly will show if you have power and ground.

It's weird. Everything test good. I.E. relays and switches but the fans aren't getting power. Would a bad A/C pressure sensor cause this problem? As the sticking caused it to be on all the time can it short and do the opposite?

I swapped relays and bench tested them with a 12v source and meter. They worked normal. Is there a hidden fuse? Check the ones under the hood and behind the door in the drivers side.

I actually had it working last night. But not knowing how I fixed it and wanting to know why. I re broke it. If it ain't broke don' fix it right?

So this morning I started the car and turned on the A/C and the fans came on. So thinking it was the A/C pressure switch I unplugged it and the fans stayed on. Plug it back in and it quit working a gain. That's what makes me wonder if it's the pressure switch.

I have a meter. Where should I start?

Thanks for the quick reply.

Can you use this:

Attachment 41332

Follow this schematic to trace the fault (when the fault is present)

Also the A/C switch specs:

Open above approx. 15.58 kg/cm2 (221.2 psi, 1527 kPa )
Close below approx. 15.56 kg/cm2 (178.4 psi, 1231 kPa )


Test the engine coolant temp switch for sticking.

Quote:

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Originally Posted by CaptainRich

Can you use this:

Attachment 41332

Follow this schematic to trace the fault (when the fault is present)

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Yah that make sense. It must be a relay. Can a relay bench test OK but still be bad? I tested the Fan to the one with the 5 blades. Had continuity between 30 and the middle blade I think I would have to check. But I had continuity when static than when I charge the outside blades it clicked then I had continuity to the other blade. But could it be that I am putting more power the relay than the car does. I used a battery tender/charger to switch the relay.

It's obvious I'm not getting power could a fuse able link fuse go bad after time? I will check those with a meter. I suspect it's the fan 2 relay the one between the ac and fan 3. Looks like it labeled radiator fan relay in this diagram.

When standing at the drivers side looking down mine are labeled Fan3 Fan2 and A/C mgn.

I will check some things tonight. Just to rule out my thought. Even it the A/C pressure switch is bad I should still see the fans come on when unplugged at the temp switch below the radiator.

Thanks,
CaptainRich

Quote:

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Originally Posted by CaptainRich

Also the A/C switch specs:

Open above approx. 15.58 kg/cm2 (221.2 psi, 1527 kPa )
Close below approx. 15.56 kg/cm2 (178.4 psi, 1231 kPa )


Test the engine coolant temp switch for sticking.

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I have a 4 prong switch which ones do I check?

Can I do these test with the engine off and just the key on or does the engine need to be running?

So today I started with the ECU-IG fuse. The fuse is good. I got 4.5v across the terminals. Checked CDS, RDI Fuses good voltage 12v across terminals. Not sure how to check terminals where the relays go in.

Check the temp switch and I have continuity. Check A/C pressure switch continuity across both sets of pins. Checked the female side of the pressure switch and had 12v. I checked the opposite side of the temp switch and had no voltage. Just not sure what to do.

Quote:

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Originally Posted by ricobot360

So today I started with the ECU-IG fuse. The fuse is good. I got 4.5v across the terminals. Checked CDS, RDI Fuses good voltage 12v across terminals. Not sure how to check terminals where the relays go in.

Check the temp switch and I have continuity. Check A/C pressure switch continuity across both sets of pins. Checked the female side of the pressure switch and had 12v. I checked the opposite side of the temp switch and had no voltage. Just not sure what to do.

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Based on the specs for that switch, if it's not under pressure (system operating on a hot day) that switch should be closed and the system would funciton. Do a close visual inpection of the terminals inside the A/C switch connector. If the switch tests good but the 'system' sees an open, you'll get the symptoms you're getting.
Good luck!

Quote:

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Originally Posted by CaptainRich

Based on the specs for that switch, if it's not under pressure (system operating on a hot day) that switch should be closed and the system would funciton. Do a close visual inpection of the terminals inside the A/C switch connector. If the switch tests good but the 'system' sees an open, you'll get the symptoms you're getting.
Good luck!

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I will check it. Getting a new Fan 1 relay tomorrow. It bench tested good but when I swapped it with the EFI the car wouldn't start. But when I put the EFI one in the fan spot still no fans. I don't know good thing cooler weather is on the way.

Ok so I put in a new NO. 2 and NO. 3 relay and nothing. So poking around inside I pulled the ENG MAIN /FR-DEF/FR-FOG relay and the RDI and CDS fuses just to make sure everything is pushed in tight.

Pushed the fuses in first and then the ENG MAIN relay and the fans came on! Sweet it's fixed. But now the fans don't go off:( Any suggestions now.

Thanks.

So I know my thoughts and trouble shooting are probably out of order but if it helps someone else this is what I found.

The ENG MAIN /FR-DEF/FR-FOG was stuck or not pushed down all the way. I'm not sure how this ties into the FAN wiring diagram as I couldn't find it in any of my diagrams. Any after I pushed it in the fans came on and wouldn't go off.

I have dealt with that issue before so I pulled off the A/C pressure switch and double checked it and the was no continuity across switch side. So I jumped the female side and the fans went off. Then unplugged the ECT connector and the fans came on yay! I found the problem.

I think what happened the first time my pressure switch went bad I overcharged it with a DIY kit. This one is only a year or tow old and I think I over charged it with a DIY kit. So I'm going to have a trained professional evacuate and recharge this time. And hopefully it will last a little longer.

Thanks for you help CaptainRich I'm sure you're a busy man and I appreciate the few minutes you stopped to help me out.

Eric

Hey CaptainRich how does the ENG MAIN hook up into this system? It may help someone else when they see this.
Thanks Again.

Quote:

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Originally Posted by ricobot360

Hey CaptainRich how does the ENG MAIN hook up into this system? It may help someone else when they see this.
Thanks Again.

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I can furnish just some of the schematic that feeds power to and from the Main Relay and onto parts of the vehicle. The entire vehicle schematic system is too large to try include everything. I'll post what is relevant or as needed.

Here's the Engine Main relay and some of it's legs:

Attachment 41390

Attachment 41391