QuestionQUESTION: This car has had A/C issues the past year or so, I added a bit of freon (134a) to it late last year, but it still isn't working properly. When the A/C is engaged and the car is cool, the cooling fan only cycles on for a second - which causes the high side pressure to drop to a temperature adjusted pressure which seemed fine (69 deg - 175psi), but when the fan is off it moves up to about 250psi. The low side pegs the gauge. Seems like it has multiple issues, but I'm not sure where to start.
Thanks for the help.
Mike
ANSWER: Hi Mike,
It appears first to be related to the loss of the fan(s). I assume this is a Sebring convertible; if not, let me know. If the compressor continues to run, but the fan doesn't then I would suspect either the fuses that run the fan relay (#9) or the fan motor (#17) in the power distribution center. If those are not cracked (which could cause an intermittent function) then the fan motor might be going out. There are two motors in the convertible so two relays. You could jump the two side pins that are parallel in those relay sockets to turn on the fans to see if that keeps the fans running or not as a test of the motor(s) and if that works, then it has to be either the relay(s) is bad, or the control function from the pcm is not activating the relay. The compressor and the relay are simultaneously activated by the pcm so if the compressor clutch closes so should the fan relays.
Those are the variables that I see in this situation.
Roland
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QUESTION: Roland,
There seems to be only one fan (it is a Conv) all the relays in the relay/fuse box are the same, so i swapped them around a bit - used the top relay for the A/C (there is none marked for the fan) same for the fuses. I jumped the fan directly at the connector and it works fine, but even after letting the car run for 30 minutes, it only cycles on for about 3 seconds every 50 seconds when plugged in with a/c running. This car was built 9/1999 in case they made changes later model year. If you think this is the PCM - which one is that it looks like 2 computers sandwich the fuse/relay box - I'm sure I will need the numbers on it to order a new one.
Thanks again for the help
Mike
ANSWER: Hi Mike,
The circuit diagram shows two separate motor windings, which I thought meant two separate motors...so that is clarified. To begin, did you notice that there are four relays in a lower/to the rear section of the power distribution center? You may have to remove the air intake at the throttle body to get to that part. The two fan relays at the very rear of the box are the low and high speed relays (high is inboard, low is outboard). The other two are the starter and automatic shutdown relays. Try swapping those out if they have the same part number. The specific fuses should be identified on the underside of the lid, or by numbering in the box: #17 might also be numbered 49/50, and #9 is 58/68. Look to be sure neither has a crack in its wire that can cause intermittency. You could also pull one of the relays when the fan dies and check that you have 12V on the inboard most pin of either relay's socket which is the volage supply to the relay point just to verify that the voltage is getting to the relay to power the fan. Then you could measure the voltage on the rearmost pin while the a/c is on but the fan is not and see if either socket's rear pin show 0 volts (that is the command from the pcm that causes one or the other motor speed to be activated). The wires from those pins go to pin 55 (low relay) and 69(high relay) of the PCM so you can check those for continuity and shake the PCM harness while doing so. If you find neither is at 0V while the AC compressor is running and the two wires are patent to the PCM I would believe that the PCM is bad.
Let me know whether all that checks out or not and then we can conclude what to do.
Before concluding it is PCM it would be wise to check the fuses, relays, wiring and the current supply just in case there is an intermittent "open".
Roland
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QUESTION: Thank you again!
I found the other relay box - didn't see it the first time - I thought it was just a wire junction. All the relays are the same, so I swapped them all around - no change. Did the same for the fuses - still nothing. I checked the voltage on the innermost pin and it is getting 12v - the back pins are getting a small amount of voltage ~.5v I can feel the high relay close when the fan comes on for its 3 second run - don't feel anything from the low fan relay. I did try jiggling the PCM harness to see if that made the relay kick on, but nothing there either. The compressor clutch is definitely engaging though.
I guess this means the PCM is bad - any chance it also controls the tach? It has been reading 700 to 1200 rpm high for a long time now - hasn't been anything that required attention - more of nuisance.
Also, is the box on the right with 2 connections, or the one on the left of the power distribution center?
Thanks again
Mike
AnswerHi Mike,
The pcm is the one with two plugs, outboard of the PDC. The PCM definitely converts the pulses from the sensors into the signal to run the tach, but it would be uncertain if the PCM or the tach itself were the issue. You can do a self-diagnostic on the cluster. With the ignition key in the 'on' position depress and hold the trip reset button, turn the key to 'off' and back to 'run'. Then watch the fireworks! The gauges go through a set of 4 presets; the tach should read 6,000, 3,000, 3,000 and then 1,00 rpm. If not then the circuit board has a fault.
Thanks for kind remarks and nomination.
Roland
PS:Before you buy a new PCM I would recommend that you try monitoring the voltages on the high speed relay when it is operating with the ac compressor in action. If you could slip a wire into each of the 4 active pin sockets (90,94,96,98,) with the opposite end of each wire accessible to your meter probe, and then insert the relay in the socket with the goal of having those wires serve as pin probes, then you could watch what happens when the fan starts and when it stops. 98 should have 12V always, 94 should have 12V when you have the engine running, 90 should have 12V when the relay closes because that is the voltage to the fan motor, and nothing otherwise, and 96 should show 12V when the AC is off, then when you turn on the AC the voltage on it should show close to 0 volts (which closes the relay) simultaneously with the fan coming on, and it should stay there, not return to 12V after 3 seconds. If instead it reverts to 12v then clearly the pcm is not doing its job of grounding pin 96 and holding it there. That would be the "acid test" for the pcm. It seems strange that it is not doing its job if that is the case.
