Radiator fan - PT cruiser - not the typical burned brushes

[bobdole369]

OK so have a 2004 PT cruiser (with the lite turbo) - the radiator fan is relay actuated with 2 speeds. The fan itself has a resistor on it for low - and you provide ground to either low or high to get that speed.

So knowing what i happen to know about these cars - when my car started bogging with the air on at lights and I felt the compressor short cycling - I realized my fan wasn't spinning.

Also knowing what I know about these cars (that they have shitty fan brushes in the radiator fan) I dutifully pulled a junkyard fan and my own out and set out to rebuild. I found instead of burned brushes, a blown fusible link in the wiring. I mean it was gone... I took apart the motor and found perfectly servicable brushes. They were barely worn. I hit them with cleaner and lube and a brush and they are like new now.

SO I repair the link replace the wires with 12ga and test. Both high and low speed work perfectly. Reinstalled in the car - no low speed. Its now sunday late and I gotta work. High works perfectly and cycles at 208 down to 200, so I won't blow my headgasket or turbo anymore from overheating.

Fast forward a bit and now I'm pissed - still no low speed fan, which means no air. 2 relays in the relay box run this - a high and low speed. I pull the high speed relay when its running and the fan turns off dutifully. Great! It works. So I replace the low speed relay (of course its different) still no go.

So now I think I need to jump the relay and just put a wire in the low speed (across the relay N/O contacts) to test?

Anybody out there ever see a PCM have an output go bad?

Of course it still could be wiring from fan to relay box too.

any advice if anyones worked on SRT's or PT cruisers?

 

[Raduque]

Fan controller on my 88 Accord died, but that was cause it got soaked ( long story).

I got nothing otherwise. Maybe go digging on a PT forum?

Edit: Yeah, jumper the low-side relay or replace it outright.

 

[NutBucket]

I know a guy here at work had to get a new ECU for his turbo cruiser. Don't know why; we just enjoyed laughing at him and the $1k price tag.

EDIT: I know my post was of zero use. Real advice; go redneck, bypass the ecu and use a simple thermal switch on the hot-side radiator hose to trigger the fan

 

[SuperSix]

Do you only see this when the AC is on?

 

[LTC8K6]

Why would the compressor short cycle in this scenario?

 

[SuperSix]

Why would the compressor short cycle in this scenario?

I'm wondering if his AC system is low on Freon, which is causing the shirt cycle, and the fan issues

 

[JCH13]

Check to make sure the wiring for the low-speed fan setup isn't shorted to the frame or other wiring. If a serious fusable link in the motor blew instead of the fuse for the low-speed power something is really wrong with the wiring.

Speaking of which, check the fuse for the low-speed operation if it is different from the high-speed fuse.

 

[bobdole369]

Compressor short cycles because high side pressure builds. It has a high side compressor cutoff switch. Engine bogs due to the high pressure before cutoff.

Main issue here is no low speed fan. It normally comes on (lo) with a/c constantly or cycles with no a/c at 200 and off at 190 on the cts.

Probably gonna ghettorig it as described if i cant eadily see the burned wire.

 

[NutBucket]

If you ghetto rig, don't forget an override to keep the fans on when the AC is running.

 

[LTC8K6]

I'm wondering if his AC system is low on Freon, which is causing the shirt cycle, and the fan issues

Me too...

However, he did find the fuse link problem, so I'll wait and see.

 

[Raduque]

Wait... this is one fan that spins at two speeds, not one high-speed fan (radiator) and one low-speed fan (AC)?

If this is the case, why wouldn't the one higher speed be suitable to run the AC?

 

[bobdole369]

I'm wondering if his AC system is low on Freon, which is causing the shirt cycle, and the fan issues

Me too...

However, he did find the fuse link problem, so I'll wait and see.

I'm really curious as to why you would think that? How would low freon cause the low speed on the fan to stop working???

My freon level is fine btw, checked with a hi/lo gauge set - the first thing I did when I heard the compressor short cycle.

If you look above you'll see an explanation for the short cycling. This car (and just about every other one) has a hi-pressure (safety) switch on the hi side (its on the compressor), and the more "known-about" low side pressure switch (the cycle switch) on the accumulator.

Since my fan stopped spinning, heat builds up in the condensor on the front of the car and is not shed at a light. This of course causes the pressure on that side to build >linearly (probably not exponentially but thats moot). Eventually - at 400 psi I believe, the hi pressure switch cuts off the compressor. BUT in the meantime during the buildup to 400psi the compressor is getting harder and harder and harder to turn. The motor bogs. Once it drops below about 200psi from advection, the compressor kicks back on and the cycle repeats. If I'm at a long light the effect is essentially the same as the typical low-freon short cycling. Most people new to the pt cruiser and its peculiarities immediately go buy a can of freon and overfill the system thinking they are low.

For the other question - yup - this fan has 2 speeds. Its actually just a one speed fan, with a resistor mounted on the shroud for low. The resistor works, and the fan work - off the car. The PCM has 2 outputs. Radiator Lo speed and Radiator Hi speed. The lo speed is active at 196 and off at like 185, and the hi speed at like 220 down to 200. Why isn't Hi good enough for the AC? Next paragraph.

When AC is on, it toggles the LO speed fan only, unless the CTS hits like 220f. I'd like to run my vehicle within design limits. The hi speed used to almost never come on except in terrible traffic. It would be perfectly fine to rig so only high is on all the time, but that would be loud. Also its not how the car is designed.

Noting that the fusible link I found that was bad was on the ground side of the fan - when that link went it took out both speeds. It's fixed now, but I still have the low speed no-go while on the car.

Another thing, this morning I jumped the relay for low speed and nada. So either no ground at that terminal on the relay, or no continuity to the fan from that terminal.

 

[LTC8K6]

I would add that fuse links don't just decide to blow. Have you discovered why the link blew?

I think your definition of "short cycle" may be different than mine. In my old Taurus, the A/C compressor runs for a very brief period, and shuts off, and repeats. It runs for maybe 6 or 8 seconds at most.

 

[nedfunnell]

You need to figure our why the fusible link blew. That's a safety feature, and if you don't solve the root cause of the link blowing, you haven't solved the problem- that could cause a fire, and we don't want that. If I were you, I'd bust out the multimeter and start checking the wires starting from the fan and working your way back. You might also check that your relay is getting voltage at all.

 

[SuperSix]

Maybe I missed it.. but did you jumper the low pressure switch and see if the fan comes on as it should?

 

[bobdole369]

Maybe I missed it.. but did you jumper the low pressure switch and see if the fan comes on as it should?

Ah yes. It does NOT come on as it should when I jump the NO contact on the low speed relay. I do the same for hi speed and high speed kicks on.

Therefore some issue exists either before or after that low speed leg. Either I don't have ground for that connector into the relay box (realllly hard to believe), or the wire betwixt low speed relay and fan is bad. I'm suspecting I'm going to find a wire melted (and then broken) to the motor when I get to it. It would explain the fusible link - esp if high came on while it was short to the motor.