Drivers Side Radiator Cooling Fan

[Mark]

When I switch the fans on, or the fans kick in with the thermo switch, only the passenger side fan turns on. Drivers side stays off. Early on they both came on together. I checked the fan connection to the drivers side fan with a meter, and sure enough, when the switch is on, there isn't power going to the dirvers side fan. Looked in the owners manual and best I could tell, it might be a relay. Any ideas?

Thanx
Mark

 

[Mark]

Ok, a little more sleuthing tracked it to "RELAYD" on page 38. Drivers fan worked when connected to passenger harness. Playing musical relays, nothing worked with RELAYD in the loop. Both fans worked (albeit seperately) when RELAYC was substituted for RELAYD.

Not being an electrical wiz, can a relay just go bad, or is this indicative of some other problem. Everything else seemded to work ok, and car stayed at 95 degrees for 30 min with one fan circualting on and off?

Mark

 

[Seymour Snerd]

...., can a relay just go bad,

Definitely.

You should be able to get another one at Pep Boys or NAPA expecially if you take the bad one with you. Just test the new one before you put it in to make sure it's pinout is the same as the one you're replacing. You can put a 9V battery across the coil terminals and should hear it click. The other way to check the pinout is to look for the European terminal numbers 85, 86, 87, 87a and 30 as illustrated below. The relay coil is between 85 and 86; the fan current flows from 30 to either 87 or 87a:



BTW, just to make sure you don't get sidetracked by something: when the A/C is on it can force one of the cooling fan relays on to guarantee air motion through the condensor even when the coolant is not hotter than the radiator fan trip temperature. I believe it is relay D that gets this treatment.

But in the scenario you describe, if the A/C is off the two fans should definitely go on and off together, either via the dash switch or the thermo switch in the radiator.

 

[Dwight]

yes, relays can fail and do fail. You need a couple of spares in your car at all times. Never know when you may need one. You can pull a relay from the horn circuit and use it, say in the fuel pump circuit, till you can buy a new one.
You can use wire jumpers from the relay to your battery to check the relay, pin 86 and 85, control circuit. You can hear a relay click when you power it up. Then you can do a continuity check on pin 30 and 87.
This link tell you all about relays and how to check them. Warning; May be to much information on relays.
http://www.autoshop101.com/forms/hweb2.pdf
If you swapped the relay and the new one works then most likely the old one is bad. All parts stores sell the 5 pin mini relay that is used in most of our cars.
Dwight

 

[Mark]

In case anyone runs into this...

Got new relay and checked every combination of relay with both fans, and then conencted drivers fan to passenger side electrics to see if it would work, and it did. However, with both fans connected drivers side would still would not run.

Thru process of elimination using wiring diagram on page 40, needed to determine which relay 'port' might on the two drivers side relays might be cauing problems. After continuity to fan check on red/black fan wire to 30 on relay D, and to red/white fan wire to 87 on relay A, it narrowed down to 86 on relay A (which happens to be where A/C system interfaces with radiator cooling fans).

So to the A/C system. Although I'm not sure just what happened, I then turned the cockpit blower on and pushed the A/C button (it turned green and I heard click from behind instrument panel). Turned them all off and then checked the radiator fans. Both worked fine for the first time since I discovered problem. Once I crank it up, I'll know if that click meant anything bad for the A/C system.