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Common AC/fan problem, uncommon solution?

 
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  #1 (permalink)  
Old 02 Jul 2010, 09:24 pm
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Location: Cincinnati, OH
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Default Common AC/fan problem, uncommon solution?

I began having the common high-speed fan not coming on with AC problem about a month ago. I have an '04 base model, so one fan, two speeds. As many others have experienced, with AC on but not moving, the compressor would kick in and cause the engine to stumble, idle would get rough, air would blow warm, and if the AC was left on it would release refrigerant due to high pressure. Took it to my mechanic, who spent the last 2 1/2 weeks trying to fix it. Ended up replacing the whole fan assembly -- didn't work. He tried another new fan in case the first one was bad -- didn't work. Thought there might be a restriction in the high-side line, so replaced that -- didn't work. I asked if he checked the two relays for the fan and the high- and low-side switches, he said all were okay. He said PCM controls the fan, but thought it is unlikely that's causing the problem. Fan comes on high when the engine gets warm, but not with the AC (comes on low with the AC, though). Mechanic says relays, switches, lines, compressor, fan are all okay according to him.

Mechanic made some calls and said there was a bulletin out on this -- today said he had it fixed and to come pick it up. When I picked it up, the "solution" they found was to install an auxiliary fan on the front of the radiator that is on whenever the key is on! Which did solve the problem, except that it is really, really loud. So loud you can't have a conversation outside the car if the engine is running (actually, if the key is on -- can't hear the engine anymore). Sounds like the PT is a Boeing getting ready for takeoff. I think this "solution" is BS. No way I can live with this. Anybody heard of this as a solution?
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  #2 (permalink)  
Old 02 Jul 2010, 10:03 pm
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Default Re: Common AC/fan problem, uncommon solution?

Nope, never heard of that fix but there has been owners that came here and told how their fix was that their mechanic hard wired the high speed part of the fan directly to the battery and like yours, would come on with the ignition and stay on all the time. Not quite as loud as yours though.

Sounds like yours is about the same except your mechanic is using a cheap, loud auxiliary fan.

You could find the wire and add an on/off switch so you can control the operation of the fan yourself.
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  #3 (permalink)  
Old 02 Jul 2010, 10:28 pm
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Location: Cincinnati, OH
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Default Re: Common AC/fan problem, uncommon solution?

Thanks Crewzin. Good idea to add a switch to that aux fan and just kick it on when I need it -- don't know why I didn't think of that (probably cause I couldn't hear myself think with that fan running). Also not a bad idea to hard wire the rad fan to be on high when ignition is on -- if that burns it out faster I can replace that myself pretty easily. And I can leave the aux fan in place so I can kick it on if the rad fan burns out.

I was a little frustrated that my mechanic was not to be able to really fix the problem, but then again I couldn't think of any other way to fix it they didn't try, and see that lots of other people have had trouble with the fans. I'll give them some points for originality. At least they didn't charge me a ton or try to sell me a whole new AC system or PCM.
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Old 03 Jul 2010, 09:01 pm
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Default Re: Common AC/fan problem, uncommon solution?

I decided to try Crewzin's suggestion of installing a switch to control the aux fan myself, so traced the wire the shop used to install the fan. What I found was a mess -- what they did was pop the fuse panel in the cabin, pull out the fuse for the wipers/flashers, and jam one end of a wire into the fuse block using one pin of the wiper/flasher mini fuse. Then they used a screwdriver to pop out a grommet in the firewall, passed the wire through the hole *next to* (not through) the grommet, and ran the wire around the side of the engine bay, directly over the battery, through the grill and connected it to the aux fan. No fuse. Over about four sharp metal edges. And the best part -- instead of replacing the grommet (not that they could have done that with the new wire there) -- they left the screwdriver in the firewall like a plug!! When I pulled that out, I could see daylight through the engine bay from the cabin. I drove back to the shop, showed them the bogus installation, and made put it back the way it was then give me my money back.

So now I'm back where I started. I did the following to check the fan: I inspected the connector and it looks fine -- clean, no melting or corrosion. I started the engine and let it warm up. When it reached operating temp, the fan kicked on to cool the radiator. If I pull the low speed relay, it goes on high, if I pull the high relay, it goes on low. I also tried swapping out the relays for new ones -- no difference. I shut the engine off and let it cool, then started it so that it is running, but not warm enough for the fan to come on to cool the radiator. I turn on the AC. Nothing -- no fan operation. The fan should kick on when the AC is on, right? I am pretty sure this is the cause of the excess pressure in the AC when it is on but the car isn't moving.

I figure this has to be an electrical/signal problem -- can't see any other cause, but the signal comes from the PCM for the fan, and the fan turns on fine if engine temps come up, so why not the AC? Could it be the PCM? How does the PCM know the AC is on? Is there an issue with the AC control unit? Any thoughts? Only thing I can think to do to solve the problem is hard-wire the fan on high.
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Old 03 Jul 2010, 09:18 pm
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Default Re: Common AC/fan problem, uncommon solution?

Yes, the fan turns on when the A/C is turned on and it's controlled by the PCM. Your best/easiest/cheapest way is with the switch.

Wow, what a bum operation that mechanic did. Good thing you checked it. That grommet will leave room enough through the center for at least 3 to 4 small wires, I have 3 (under car lights, Ahooga horn, amp wire) going through there myself.
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Old 04 Jul 2010, 09:18 am
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Default Re: Common AC/fan problem, uncommon solution?

Wow what a hack of a mechanic! If you have a good dealer near you it may be worth paying for at least having them diagnose the problem. Not that the dealer can't be a hack also.
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Old 04 Jul 2010, 10:39 pm
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Default Re: Common AC/fan problem, uncommon solution?

Thanks Dino. I agree -- may be worth a trip to the dealer. Bought my PT used and have never been to a dealer with it, so not sure if there's a good dealer near me. I'd actually never taken it to a shop before -- did everything else myself (with a lot of help from searches of these forums!). I may ask around and see if there's a good dealer in my area (Cincinnati).

I think I've eliminated everything but the PCM in this case. Fan works fine -- high and low -- if you just apply a 12V to the fan. Fan also works -- high and low -- when the engine needs cooling. I've never had any overheating problems. It just doesn't come on for the AC.

I think I may just mount an auxiliary cooling fan in front of the condenser, except that I'll get a better fan, use a fuse and relay to wire it safely, and switch it with the AC compressor so it only runs when the AC is on. That would cost me less than $100 to do. I hate not solving the underlying problem, but honestly prefer just to deal with it myself at this point. I could hard-wire the existing fan on high, but I think that may trigger a CEL, and it would be on all the time whether needed or not.
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Old 06 Jul 2010, 10:39 am
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Default Re: Common AC/fan problem, uncommon solution?

Good idea. You can get a relay to be triggered by power to the A/C compressor to power aux fan.
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Old 24 Nov 2010, 12:27 am
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Default Re: Common AC/fan problem, uncommon solution?

Quote:
Originally Posted by p_ridge_pt View Post
Mechanic made some calls and said there was a bulletin out on this -- today said he had it fixed and to come pick it up. When I picked it up, the "solution" they found was to install an auxiliary fan on the front of the radiator that is on whenever the key is on! Which did solve the problem, except that it is really, really loud. So loud you can't have a conversation outside the car if the engine is running (actually, if the key is on -- can't hear the engine anymore). Sounds like the PT is a Boeing getting ready for takeoff. I think this "solution" is BS. No way I can live with this. Anybody heard of this as a solution?
Hi there, Have you already did the installation? I am helping my friend to install his auxiliary fan. I guess you both have the same problem.The mechanic told us to install this fan.

Last edited by clarkadnrew45; 29 Nov 2010 at 08:41 pm.
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Old 03 Aug 2017, 08:10 pm
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Wink Re: Common AC/fan problem, uncommon solution?

I know this thread is old, however, I thought I might help someone with an easy fix. We have several PT's for our IT business. Two of them have the same issues as everyone else: the low speed on the fan motor burned out. We of course tested the fans by directly connecting to the battery and sure enough the high speed worked but the low speed doesn't. We ordered fans but until they get here, the techs wanted AC. I stumbled upon this article and had a thought. Not sure if this is a recommended fix, but here is what I did to get things cool and working again.

I jacked up the PT, crawled under the front, and disconnected the fan plug closest to the fan (the three wire plug where the wires go directly into the fan motor). Once disconnected, I used wire splicers to connect both the low power and high power positive wires together ((dark green and yellow I think....but in my case they were both blue). Since the low power resister is in the fan motor itself, we essentially bypass the low side all together. When the ac is cut on, the PCM signal is sent to the lower speed relay but the power actually gets sent to the high speed side of the fan motor due to the splice over. The fan in return powers on at the high speed setting. Since the splice is done at the fan end after the relays, it doesn't cause engine codes and sure enough ..the low side signal spins the fan on high and the high side signal, still spins the fan on high as well.

The only down side is that your fan will operate at full speed anytime the AC is on..however, since I use AC in the summer the windows are up and i really don't even hear the difference. Worst case, the car stays cooler in the summer.

Anyway, thats a 5 dollar fix (maybe temporary) instead of an 80 dollar fan and some labor.
Just thought I'd share.
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