iceberg

Currently having a problem with the electrical system (battery charging issue) that appears to be related to my PDAS/ABS control system. When I went to start my car recently the battery was drained and if the car sat for more 5 hours the car would not start.

First I hooked up a multimeter to determine if there was any excessive battery drain (no problem there). Next, I tested the alternator (no problems there).

I had recently worked on my PDAS/ABS system which had not been functioning for some time and finally got it working (replaced wheel speed sensor and cleaned the connectors to the PDAS control unit). So I thought that might be part of my problem. I disconnected the PDAS control unit and sure enough my battery drain issue was gone. For some reason when my PDAS control unit is hooked up, the battery does not charge. I have a spare PDAS control unit and tested the system with it. Same battery drain problem. Also, my air conditioning stopped functioning at the same time as the battery drain issue. The defroster and interior fans blow, the condensor turns on, condensor fan works, but no cold air at all. Any ideas.

garrett376

Couple of questions for ya':
What kind of car do you have? C4 is obvious, but what year, location are you in, etc? (save Adrian that question!)

Does the air conditioner work if the PDAS control unit is unplugged? When you say the condensor (compressor?) turns on, you mean the clutch engages it so it turns (not just the pulley, but the entire assembly?)? If that's the case, it sounds like you've leaked out all your refrigerant.

When you say you got the PDAS to work - do all the warning lights appear when you turn on the ignition before starting the engine, and none remain on or come on during driving?

Just trying to help clarify this.

DaveK

I assume when you say condensor turns, you mean compressor?

If the compressor turns - you have refrigerant, because the compressor won't engage if you run out.

iceberg

The car is a 1990c4 and I am located in Washington D.C. The air conditioning does not work when the PDAS unit is unplugged. When I push the AC button I hear the compressor turn on. Not sure on how to check if the condensor is functioning. The AC problem began the day after my PDAS repairs. Before that it worked well (blew cold air).

When I repaired the PDAS the warining light and ABS light on the insturment cluster showed on the dash for approximately 10 seconds and then turned off. Also, when driving the ABS worked and the PDAS light on the console flickered when driving the car agressively and flashed when the differential locks were engaged via the central console switch (next to spoiler switch).

garrett376

Good call Dave, that's right! But, iceberg may think it has engaged, because doesn't the clutch click, then because there's no refrigerant, quickly disengage? That might be confusing thinking it is actually on based on clicking noises alone. You'd have to stand back there and have someone turn on and off the A/C to watch to see if the entire compressor and clutch assembly is rotating, not just the pulley.

If it does, then it sounds like something is up with the air mixing handled by the Climate Control Unit. I'd do a search for CCU - I've come across lots of garble about that stuff.

garrett376

Regarding the PDAS, if you cleaned the pins, and still have the problem following your fixes, then I'd check to be sure there are no smashed pins on the PDAS plug - you could have a short. Additionally, make sure the harness is not mashed up anywhere - again a possible short (or ground). Also check your wheel speed sensor plugs to be sure they're plugged in well and not shorting - following the wiring around.

If you unplug your "repaired" wheel speed sensor, but leave the PDAS plugged in, despite the warning lights - do you still have a current drain? That might be one way to isolate the problem...?

DaveK

I think when mine ran out of refrigerant, the compressor didn't even click in. But I don't think you need someone else to check it - if you switch it on, you will see whether it engages properly because the "face" of the compressor wheel won't turn if it's not engaging (only the belt pulley will). My compressor cycles on and off - and I remember a thread a year or so ago where Adrian said it shouldn't - but everyone elses did (to stop icing up).

You can also check the condensor. Switch the A/C on with the engine running - go around to the front left of the car and listen just in front of the front left wheel. You should hear a fan running. If you don't, then your condensor fan isn't working. If it's working but cycles on / off every 5s or so then your ballast resistor is dead (common problem).

iceberg

I unplugged the "repaired" wheel speed sensor and plugged the PDAS unit in. Still have current drain. Checked the PDAS plug and harness no smashed pins or other noticable issues. Question, if there was a short somewhere in the system wouldn't this likely cause the PDAS/ABS system to fail (not function, with warning lights on)? Any other suggestions on where/how to look for the currency drain?

Also, the condensor fan is operational. Will need to do a little more investigation on the compressor and also determine if my system is properly charged with freon. Just seems odd that both of these issues occured at the same time. One of these day I will get everything function correctly at the same time!!!

garrett376

If your PDAS is fine, why don't you pull the fuse or relay involved with the A/C (climate control) and see if you have a current drain that continues. Maybe the PDAS is fine, yet the climate control system is the reason for your current drain. You can at least rule out the climate control system as a source for the current drain.

By the way, how are you measuring the current drain?

iceberg

Will try to pull the fuses/relays. I will pull #1 blower inside compartment, #17 heater control, #39 condensor blower. Do you know what relay(s) relate to the climate control unit? Still think the problem has to be with the PDAS system since when it is not hooked up I do not have the battery drain issue. I was testing current drain by hooking up a multimeter to the negative battery lead to measure drain when car was not running. Thanks.

garrett376

You're probably right, but at least we can rule out the current drain from the climate control system. No relays I know of for the CCU - I just checked the wiring diagrams (sorry).

Does your ABS work correctly (on the road)? There are separate relays for the ABS unit - is it possible one of those is malfunctioning and causing a drain? In the central electric R34 is the ABS relay - if you remove this, you would disable the ABS, right? That might be a place to check if your drain disappears with the removal of this.

iceberg

Disconnected the climate control system and the battery still does not charge. From my understanding, R34 provides over-voltage protection to the PDAS unit. Would be hesitent to remove it (don't want to fry the control unit). Any other suggestions on measuring current drain? Back to the drawing board.

garrett376

I don't want you to fry it either - but if you have a fully charged battery, at 12.6 volts (whatever it might be), it won't produce more voltage to the PDAS as long as the engine is not running. I would think you would be able to pull the relay with the car not running, and see if your continue to lose a charge on the battery - with no worries that an overvoltage would be produced.

DaveK

I'm a bit confused by what the actual problem with your battery / charging is. In the original post, you say that you checked for excessive drain and there was no problem - so I originally assumed you had some kind of charging problem. But some of the recent posts suggest it is actually a battery drain problem.

So - just to clarify :
Are we talking about the battery going flat if the car is left unused?

Or do you think something is stopping the battery being properly charged by the alternator?

What is the current drain on the battery with the ignition switched off?

How old is the battery?

iceberg

Problem is the battery does not properly charge when the car is running and the PDAS system is functioning (battery not being properly charged by the alternator). If I disconnect the PDAS system while driving no problem with battery charging, if the PDAS system is hooked up when the car is not running then no excessive drain noted (via multimeter). Current drain with the ignition switched off is around 40ma. Not sure how old the battery is (probably around 3 years old).