I upgraded this question, because I have the exact same problem on my car. I lost AC last year, and this week had to replace the water pump, after I noticed that the fans aren't turning on at all when you put on the AC and it eventually led to a broken water pump impeller. My car is a 1998 Mercury Sable LS DOHC. I tested the plug going to one of the fans, and with the AC on, I couldn't get any voltage or amperage to the fan itself. I believe both fans work, though they are a pain to even attempt removal, let alone test.
What is the relays for this car, as lat's car has a different box diagram than mine. Oh and the radio loses sound when I put it in reverse. That might also be an issue.
July, 4, 2012 AT 9:06 PM
1998 has a different fuse box design and the schematics are slightly different as well.
Radio losing its sound could be due to a bad ground circuit somewhere and it most probably should be around the radio.
July, 4, 2012 AT 9:20 PM
Thanks for being online today, thought I'd have to wait til tomorrow to find out which relay to test. On that note, how do I test relays for cars. Last time I did it, I blew one up, and had to replace it anyhow. The fuses are good, I should probably test the fans themselves, but since they're not getting power, I'm assuming 1 or both relays is shot.
Would there be anything else to test if the relays are good?
July, 4, 2012 AT 9:25 PM
I added an image to clarify the 2 relays.
July, 4, 2012 AT 9:38 PM
Actually I was about to log off for the day.
If you refer to the wiring diagram, yyou would notice that the relays are labelled 30, 85, 86 and 87 for the terminals.
You relay is labelled differently and has 5 terminals. The center row is actually terminal # 30 (single pin) while the other 2 pins are terminal # 87. One of your relay has the wordings 2, 4, 3, 5.
@ and 4 are the coil circuit whereby if battery voltage is applied to one and and the other is grounded, the relay would click.
One simple way is to sway the relay with another that fits, eg the headlight relays. You can use the headlight to test the realy too. Just remove the headlight relay and plug the fan relay in and turn on the headlights. If the headlight fails to work, then you would know the relay is bad.
July, 5, 2012 AT 12:01 AM
I did the simple way, and both of those worked. I swapped the relay for the fuel pump and I still had fuel pressure, and checked just in case, and pulling it caused the car to stall.
Likewise I swapped the relay for the starter relay and pulling that wouldn't start the car, but both relays allowed the car to start, so that relay is good.
Now what should I do?
July, 5, 2012 AT 12:58 PM
Sorry I made an error with the relay teminals. Terminals 1 and 2 are the coil whereas 4 is the power supply and 5 and 3 are the output.
Unplug the relay and check terminals 3, 4 and 5 of fuse block for battery voltage. Depending on which relay, low or high speed fan, there must be one terminal that is hot at all times. If terminal 4 has battery voltage, use a fused wire to connect it with either terminal 3 or 5 and see if fan comes on.
July, 5, 2012 AT 1:58 PM
If I'm doing this correctly, according the the numbers on the relay itself, corresponding to the holes on the fuse block, starting with the red wire plugging in from position 3.
3 to 5 gives me 12 volts.
3 to 1 gives me 12 volts.
3 to 2 yields 0.25volts.
There is no metal prongs in position 4 on the smaller relay for the center #4 position.
If I'm not connected to position 3 (the farthest lead not in line with 3 prongs, I yield no voltage for say 2-1 or 5-2 or 5-1.
July, 5, 2012 AT 2:04 PM
Likewise on the fatter Relay, holding on position 30, I get 12 volts on position 86 & 87, 0.5 volts on position 85, and center 87A is unused. No voltages present if one lead is not on position 30.