Diagnostic Tech: Finding the battery drain.

Sometimes things don't work out, sometimes they do. A little over a week ago I had a good customer bring his '09 Mercury Grand Marquis with two complaints. Occasionally the battery would go down overnight. The same problem was there after he had the battery replaced. The second complaint was that the radiator cooling fan had stopped working and caused the a/c to release refrigerant. The radiator cooling fan not running with the air conditioning on would allow the system pressure to get too high. There is a pressure relief valve at the bottom of the compressor.
Whenever I am going to be testing for a battery drain I want to know the condition of the battery. This battery had been on the car less than a month but tested bad. I needed a good battery on the car while testing so installed one from my own stock. I forgot something very important. New does not mean good. We'll come back to that.
With a new battery on the car I did charging system tests and battery draw tests. The battery draw would be where any excessive battery drain would show up. Battery draw was fine at this time so I was probably looking at an intermittent problem. There was the possibility as well that the original battery was bad but so was the replacement. Not likely, but possible. I told the customer I should keep the car overnight and see if anything showed up as a drain. That being settled I moved to checking the cooling fan. The fan was working at this time. So far, I was getting zero co-operation from this car! I have seen a lot of problems with intermittent cooling fan operation on these though. The system is usually fine after replacing the fan module assembly. Rather than wait for the fan problem to appear at a bad time it was decided to replace the fan module and recharge the a/c.
No battery drain happened overnight, the car cranked fine, the a/c worked great and the cooling fan was fine. We put the bad battery in the trunk and left my new battery in place on the car. I parked the car outside and about an hour later the customer comes to pick it up. It wouldn't crank. The battery was completely dead. I was completely at a loss for words! After stuttering and sputtering and head scratching a bit I just started testing from the beginning. Remember "new does not mean good"? When I tested my new battery it was bad. I don't mean discharged, I mean bad as in not good. I pulled another new battery but tested this time. Testing good, I installed yet another new battery. I told the customer to let me know of any problems. I was still pretty sure the car had an intermittent drain but after this unforeseen battery fail fiasco I was off my game just a bit. He had no other ride and no time to wait for another battery draw test.
Let us now move forward. The car was fine for several days before once again draining the battery overnight. It was arranged to leave the car for at least a couple days if needed. Once the car was dropped off I parked it inside the shop to get it prepped for tests. First, test the battery. My preferred tester works best if I connect it directly to the posts with the car's wiring completely out of the picture. Especially when I could have a problem with excessive draw. I have a "memory saver" unit that connects to the car diagnostic connector and provides power to the car electrical system while I have the battery disconnected. This preserves memory and prevents a sudden power loss that could affect any cause of excessive drain that might be present.

Battery was good, slightly under a full charge but good. I reconnected the battery, put the memory saver away and tested the charging system. 

Good battery and good charging. I shut everything off and figured I would put the charger on to top off that battery while I was waiting for the cars computers to go to sleep. After that I could test draw. Now I had noticed the 96% capacity on the battery test results but the charger showed 90%. 

This bothered me a bit. It made me keep a closer watch on the charging progression. After about a half hour the 90% was still 90% and that was odd. I decided to test the battery draw. Depending on the system if you check draw while a computer is still active you expect 100 to 400 mA. If the system is asleep you are looking for about 50 mA, again depending on the system. 

Wow! Something was on and it was more than a computer not sleeping. It was by now shop closing time but if I didn't find this now it might not be there in the morning or the battery would be down and I'd have to start all over. Or both. I decided to find this problem while it had decided to give me a chance. The next step was to find which circuit had the draw. For that you begin pulling fuses and watching the meter. I started with the underhood fuse block and the smaller mini fuses. These fuses will usually have fewer things on the circuit that they power. Once you find which fused circuit the problem is on you have to trace further to isolate the component of that circuit causing the drain. 

Decide where to start when pulling the fuses and follow a pattern. It also helps to take a "before" picture as a guide later just in case you get confused as to where the fuses go back. Have a place to lay each fuse as it comes out. I try to re-create the same pattern as was in the box. As you pull each fuse you'll want to watch for the meter reading to drop. If you pull a fuse and there is no drop don't put the fuse back. Putting the fuse back could trigger another system to kick on and now you aren't looking at the same draw. I started with that green fuse at the top right and went down that row. 

Not much was happening until I pulled that last blue 15 amp fuse next to the bottom of the row. Then the meter showed I had found the circuit with a problem. Something that fuse powers was causing the battery drain. 

Before going further on though it is best to close up the other circuits. To me, it makes things less likely to lead to false conclusions if I keep the system as intact as possible. I put back all the fuses except for the one with the problem. If you put a fuse back at this point and it does wake up a system, you wait for the timeout and go on with your diagnostics of the problem. In this case though no other draw appeared and I was only with one fuse out of the block. 

Now it was time to find out more about this fuse and what was on it. I just stuck the fuse into the block once again and noticed that besides the draw jumping back up on the meter that I heard the a/c clutch on the compressor kick on. I distinctly heard the click. While that did seem like a big clue it could also be a false lead. There might be a software program in place that has the computer cycle the clutch once anytime that circuit powers up. You have to find out just what fuse this is. The fuses are numbered and the schematic is on the fuse block cover. According to the cover I was looking at fuse 11. 

A quick check of the wiring schematic for fuse 11 shows it to power (surprise!) the a/c clutch relay. 

I put the fuse 11 back into the box and pulled the a/c clutch relay out instead. The draw was gone. The relay was powering the a/c clutch even after the car was off and sitting parked. That was the battery drain. The relay was stuck or something in the wiring was closing the relay. It seemed like it would be a simple check to take one of the other relays (same part #) and place it in where the a/c relay was before. I did that and there was no draw. I put the original a/c relay back in and the draw came back, clutch kicked on. The a/c relay was stuck on. 

I replaced the a/c clutch relay this morning and patted myself on the back a few times. I have to say the car was much more co-operative the second time 'round. Just a few more pictures, bear with me. I wanted you to see what is a typical key off battery draw on this car with the computers still awake. (after the fix)

After the computers go to sleep.

If you know me, you won't be surprised that I just had to take that relay apart. I was amazed at the picture I could get with the iPAD. You can see the contacts that were burned and sticking. 

As always, hope this helps you. 

Kenneth Hayes

G&G Auto Repair

Under the Hood series: Basic Recovery Cooling System Inspection (or How do I check my coolant?)

Most people know that the car has something in the radiator to keep it from overheating. In the summer it's usually called coolant, in the winter it's usually called antifreeze. The radiator and the coolant/antifreeze are part of the engine cooling system. As the coolant heats in the cooling system it expands and because the system has a pressure cap the system creates pressure. Each system has a recommended pressure. The examples I have here today are a '83 S10 truck, 01 Nissan Frontier and 06 Toyota Avalon. The S10 uses a 15 psi pressure cap, the Frontier a 13, the Avalon a 16. You can usually read the cap psi on the cap.

Make sure your cap matches the OEM specs for your car cooling system. 

As the coolant heats, expands and pressurizes it will sometimes reach more pressure than the system wants. The cap has a spring loaded seal that will open and allow some of the pressure to be released as overflow. Once the pressure is lowered, the spring will reseat the seal and stop the flow. This is how the pressure cap regulates the system pressure. There was a time when the overflow tube was connected to a hose that just directed the overflow coolant under the vehicle and onto the ground. Not only was it not evironmentally friendly but checking radiator coolant level and topping it off was something you couldn't neglect without causing overheating and possibly expensive complications. Also, "topping off" did not mean fill to the top. You had to allow room for the coolant to expand. A radiator has a core and two tanks. If the tanks were across the top and bottom, allow 2" of space for expansion. If the tanks were along each side, 4". 

Overflow systems no longer go directly to the ground. Newer systems direct the overflow to a coolant recovery tank. Overflow collects in the recovery reservoir as the cap releases pressure hot and as the system cools the coolant is drawn back into the radiator. The recovery tank on these systems is not under pressure and has either a screw-on type cap or just a snap-in-place type. It is simply a bottle to hold coolant for the radiator until needed. 

There are usually marks on the outside of the recovery reservoir that you can use to determine if there is a need to add coolant. There are two level marks, one for minimum and one for maximum. If yours says hot and cold instead of min and max, just think of it as the latter. As long as the coolant level is between the two marks you are fine. Don't obsess over keeping the level at one mark or the other. It varies.

Now just because the level is in range at the overflow reservoir doesn't mean your radiator coolant level is good. The recovery bottle reflects only what has gone through the overflow hose. It is possible to have a low radiator level and a full recovery bottle. If your cooling system has a leak it may not create the vacuum needed to draw coolant back from the reservoir as it cools. To check your radiator coolant level you'll need to remove the pressure cap. Do that only after the engine has cooled completely and has no pressure on the system. You can feel the top hose and give it a squeeze to determine if it has cooled and has no pressure. Once it is safe to open the cap you'll need to press down firmly on the cap to overcome the spring. Press down firmly and turn the cap counterclockwise to a full stop. Once the ears on the cap are aligned with the open spaces on the radiator you can pull the cap straight off. 

While you have the cap off is a good time to inspect the condition of the cap seals. If one or both is cracked, swollen, missing or damaged you should get a new cap. Look down inside the radiator for the coolant. Some designs are better for that than others for determining coolant level with a quick look. The S10 truck lets you see down into the radiator very well. The level is slightly lower than it should be but not terribly so. You can see the mineral deposits on the tubes but they are still open and no overheating. The system was topped off to bring the level more into the expansion range. 

This Grand Caravan has a design that offsets the neck and doesn't allow such a good view. In this case the coolant level could be fine but just out of sight. If your car is like that just add a slight amount of coolant to see if the level will come into view. 

Some manufacturers make it difficult to even find the radiator cap. 

What to add? As usually is said, check your owners manual. You may be more confused after though. When you check the owners manual it usually looks like the safe bet is go to the dealership and get your coolant. Technical information

Basically, if your radiator is old school and made of real metals you use the old standard green antifreeze/IAT. If your radiator is an aluminum core with plastic tanks you use one of the universal extended life antifreezes. 

The next thing to bear in mind is that your coolant is a blend of 50% water and 50% antifreeze. That mix is recommended for best protection with no problems. If your chosen antifreeze says it is a concentrate then you'll have to make the coolant mix by adding equal parts antifreeze and water, preferably distilled water. This is why you can also find pre-mixed coolant 50/50. It's ready to pour into the system as is. If your cooling system has always been properly maintained and you know the coolant in they system is a 50/50 mix then all you have to do when you see it needs a topoff is to add a mix you've made or a pre-mix. If you've no history available the car could possibly have coolant that is mostly water, or even mostly antifreeze. You can determine what sort of mix is in the car though. If you look at the chart on the back of most antifreeze bottles you can see that a 50/50 mix provides -34F freeze protection and 266F boilover protection. 

You can use one of the hand-held bulb type antifreeze testers to determine the mix. This particular tester shows that if you see 5 balls float in the sample then it is good to -34F. Since you need a 50/50 mix to get -34F that will that let us know if the mix is correct. 

Those testers work very well with the standard green IAT coolant and may work just fine with later coolants as well. I wasn't sure though so usually on later systems I use a refractometer for testing the mix. 

So we've covered some basic cooling system maintenance. How to check the coolant levels, what sort of coolant and what sort of mix. I've mentioned checking the radiator cap seals. It is also possible to pressure test the cap. A cap that doesn't hold enough pressure will release to much coolant to the overflow. 

When you are finished and ready to install the cap be careful that the cap is fully fastened. Some caps have arrows that will be aligned with the overflow tube when fully closed. 

I want to mention something before I wrap this up. The cooling systems we've been looking at are recovery type. The coolant that is released from the system goes to a coolant recovery bottle and is stored for recovery once the system cools. There is another type that may appear similar but is not the same system. The tank on this system is the actual cooling system reservoir and under system pressure. You would take the same precautions before opening this cap as you would a radiator cap. Let the engine cool completely before opening. The radiator on this system has no cap and isn't readily accessible. The coolant is added to the reservoir if needed and there is no overflow bottle. 

As always, thanks for reading and I hope this helps you in some way. 

Kenneth Hayes

G&G Auto Repair