Contour Enthusiasts Group Archives Forums General Troubleshooting Mystique Not Charging

I am having a charging problem with my 1995 Mercury Mystique. The car was running fine with no problems at all and then after a thunder and lightning storm the battery light came on when I started the car. By the time I got the car home (Appx. 35 mi) everything went dead even the tach. It started up the next morning and drove it to the shop (barely made it) to get the alternator replaced. The tech also said that the battery was junk. I got a new Alt and Bat installed and the tech said that the alternator wasn�t putting anything out so he had to replace it. After the replace it still wasn�t charging. They looked at it all the next day and still nothing. They told me I had a drain and that they were not the right people to take that task on. I followed the procedure in the Haynes Repair Guide to check for the drain. I disconnected the alternator and the test light lit up between the neg battery post and the cable. I then pulled every fuse (Including the main and all of the relays) one by one checking the circuit but the test light still lit up every time. There are no modifications to the car and it does have the factory alarm. I call an auto electrical shop and they said it would cost me $30 just to hook it up to the machine. Any suggestions???

I�m not sure if the Haynes procedure is correct. What you want to do is disconnect the neg battery terminal and connect an amp meter between the disconnected terminal and the neg bat term. You should only read .05amp (don�t quote me on this). If you read higher then you have a drain. If you see a large drain with the fuses and relays out then it is possible that the replacement Alt has a shorted diode. You can pull the mega fuse and see if the drain clears (that will confirm a shorted diode). I think the mega fuse is located on the firewall behind the coil. However, I�m not sure on a 95.

jeff

What do you mean by the mega fuse...are you refering to the Main fuse?

After searching the forum for "Mega fuse" I know exactly where it is! I was wondering what that was and could not open the little black plastic box. I will try it again over the weekend. THANKS!!!!

P.S.There are quite a few posts with this problem but could not find them when performing a search with out "mega fuse".

I checked and replaced the mega-fuse (THANKS FOR THAT INFO!!!!). It was bad! I started it up and tested for charging but still nothing...the battery read 12v and dropped a little with everything running. The idle was high and kept it going for a few minutes and still no charge. As i was checking continuity between the megfuse and the pos side of the battery I also checked it to ground and the meter moved to show no/little resistance. I disconected the main fuse box from the battery and the short/drain from the megafuse to ground went away. I hooked up the main and disconnected the interior fuse box and the short/drain went away. I then started checking the current drain with every thing hooked back up.
I pulled the two long output connectors on the interior fuse box. Found that the bottom clip of wires in the left connector and the third clip down on the right connector, when pulled, stopped the drain. Couldn't figure out what circuit these two clips are used in. So I re-connected everything and then started pulling fuses. When I pull fuse 35 (a 7.5 amp fuse that is listed as the Right Side Parking lights) the drain went away. I tried starting the car with that fuse pulled but it would not start and then when the battery was connected the alarm went off after a few seconds. This fuse must be part of the alarm circuit as well. I put the fuse in and started the car, pulled out fuse 35 but still no charge! ANY IDEAS?????

Hmmm.. you know it's possible that the new alt is dead.
You should just take it to another shop that works on
eletric systems and such. Odds are you have a Ground Short
some place and without the right tools those are very hard
to find. Also when they put in the new Alt and Bat did they
try and replace the wires as well? Sometimes it helps...

I think you need the ford manuals and not that crappy haynes book. It gives you just enough to blow yourself up.

You need to charge the batt (with the - side disconnected). Reconnect all of the wires, fuse boxes and install all the fuses. Then with the battery charged, ign off and all doors closed, connect a DC amp meter (10A scale) from the _ batt term to the ââ?¬â?? batt cable. If you read more the 1 amp, disconnect the Alt by first pulling the mega fuse and recheck. If still high, pull the plug regulator plug out of the back of the Alt and recheck. If the drops to below 1amp with the fuse or plug pulled, the alt is bad.

The regulator plug has two 12 volt feeds, one drives the ALT lamp and the other is the reg reference Check for 12v with the ign on. On some models the reg ref line is protected by a fusible link. The Alt light ckt is protected by a 7.5A fuse. Chances are if you mega fuse was blown they are too. Lastly, pull the batt and try and check for corrosion on the wiring harness.

jeff

I agree, I've also had a problem with corrosion on the wiring in a 98 Mystique.

Mercman/Jeff,

I finally got some time over the weekend to look into this problem again. I checked/did everything you mentioned in your previous posts. I will recap what I did over the weekend.

1. Checked all fuses and all are good
2. Checked mega-fuse, still good after replacing.
3. Charged batt and Checked for drain with all doors closed. Checked out to be ok apprx 30 mA, when release hood switch, the current shot up. So I take it that there is no drain.
4. Checked for corrosion - None.
5. Checked wires on alt. 12v on Grn/Blk when in run position, 12v on red always, 12v on mega-fuse, continuity btween the gray wire in the plug and the gray wire that connects directly to alt.
6. When I pulled the 7.5 amp fuse for the engine management system, the 12v on the grn/blk wire going to alt went to zero.

The one thing I did notice is that the batt light in the dash does NOT come on when I turn the key to the on position. This was working (when the key was in the on position and also when stepping on the accelerator) when I took it back to the shop the second time. When I picked the car up from the shop the second time after they couldn't find the problem, I did notice that the batt light wasn't coming on!

Can you think of anything else????

Thanks in advance!
Paul

Over the weekend my alternator light came on, and I figured it was a cut-and-dry bad alt, even though this was already a replacement. I've never heard of a mega-fuse... and I went through the literal agony of changing the alternator on a V6, with nothing to show for it. But I got more heartaches: the insulation from the wiring branch that bolts to the positive cable and goes to the underhood fusebox is shattered and the wires exposed. How much a problem does this actually cause?