On my 2000, I have come to realize when I run the cooling fan the battery begins to lose voltage (gradually loses it). With the cooling fans not running voltage is maintained properly by the alternator.

Any ideas on where I should be looking? I am thinking cooling fan relay 1 may be suspect.

Here is a little history:
Car started to run hot last summer. Found burnt wire leading to one of the cooling fans (passenger side...I think this might be #2). I replaced the entire fan assembly (both fans included). I found one of the large fuses for the fans was blown in the engine bay. This was the fuse in the engine bay near the battery. I replaced that. Car will run fine but will not maintain proper voltage on the battery. Car has been sitting since last summer. Now here I am.

While testing to ensure everything was working as expected, I found the battery was losing voltage. By chance, I came to realize that if the fan was not running voltage was maintained just fine. I ran a series of tests such as running the car with all accessories on and voltage was maintained properly (between 13~14 V). When I would engage the AC from the controls on the interior, the voltage would trickle down and never recover unless I turned the climate control OFF. I did notice running in ECON mode had no effect. I point this out because this IS part of the climate control system, it was turned on, and had no ill effect on the voltage. I was thinking this had something to do with the AC. Here is what changed my mind: the secondary fan kicked in once the engine temp warmed up enough and the ac was completely off. The voltage began to drop then, too. So, it appears running of the fan period is what is pulling down the voltage and not necessarily running the AC compressor.

I've tested every fuse under the dash and in the engine bay and all are fine. I'm about to start testing relays (cooling fan #1, #2, and #3).

The question I have is does anybody know what could be causing this? If a relay were defect, would I see this behavior or would the fan just not work? I do have the ESM that outlines the testing procedure for relays and I am going to start there unless anybody has any suggestions.

Thanks for any help or tips.

 

My first guess would be the alternator. It isn't able to supply enough power to run the fans, hence the voltage drop. Now it could be the alternator itself or the belt that drives it.

 

I took the alternator off and had it bench tested at Advance Auto Parts. The same guy ran the same test on a new off the shelf unit. Same results for the one off the car and an off the shelf one. I, too, immediately thought alternator.

I replaced the belts a couple weeks ago.

 

perhaps you know the storry better but i have reason to suspect you have some problem that overheated your wire and took out the rad fans since you replaced it. I would start doing voltage drops from relay to fan and on ground side. You have the manual so look at wiring diagrams.
It cannot be the relay or i doubt since a relay is a switch that is controlled by low voltage ECM to turn higher voltage i.e fan. If you wanna be sure just swap with another one of the same colour and Part # in relay box. Usually there are 2-3 of same colour.
I suspect you may even have not repaired that harness properly and you might have excess resistance at repair causing more current to be drawn from the charging system.

 

Check your fan connectors and be sure the terminals are clean (free of any corrosion) and that the connector itself is good and tight with the chassic connector! Sounds like you have a loose connection or stuck relay! Unplug your relays and check for continuity between the contacts not the coil. there should be a little schematic on your relay with the pin #'s.... Also check all your grounds on the engine! maybe one is loose or, corroded, or broken...There are several at the altenator and passenger side frame rail check them all! If any corrosion is evident clean and reinstall ! Once installed brush them with some paint or spray them with some LPS 2 or 3 (forms a wax coating)...Good luck!

 

When the fan assembly burnt out it may have semi-melted a wire so it can go to ground a bit therefore causing the voltage drop but it isn't bad enough to blow a fuse. Check the resistance of the fan plug, unplug the fan and check(put a probe in one terminal and put the other probe to a ground and then repeat with the other terminal) one terminal should have infinite resistance(power wire) while the other terminal should have a low resistance(ground wire). If that checks out OK then check the wires at the relay in the same manner. You can also check the resistance of the fan motor to see if that is within spec.

 

Thanks for the feedback. I should clarify the "burnt wire" I referred to that I found orginally was the wire on the fan motor. When I replaced the fan assembly (it came with the motors) the wires were good. This is why I was looking outside the fan assembly (it seems to operate fine).

The first thing I will do is swap some relays around to see if that has any effect (this is the easiest thing to do).

I do plan on checking relays and circuits at this point. I'm not that good on the electrical side of things so I seem to struggle in this regard even though I do have the diagrams. I'll give it a whirl to see what I can turn up.

 

I was desperate and ordered a fan relay. I put the new relay in position Fan Relay 1 (out of 3). There was no change...voltage slowly dropped. I proceeded to remove Fan Relay 3 (this was the one almost always working), and I was thrashing around trying to remove it I noticed the voltage starting to climb on the battery (I had the meter attached the whole time). So, it appears this relay may have been loose (I never did take it out). After wiggling it around the ship seemed to right itself. Fan on and the voltage maintains proper levels. Lesson learned.

The voltage still drops I notice when the headlights (only) are turned on. This is another battle.

 

than take it out and clean terminals with contact cleaner. You can even apply some dielectric grease after before you put it back

 

sounds like you mave have melted your relay box! remove it and turn it over to see if it has heat damage!