A/c issue
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Junior Member
Joined: Sep 2009
Posts: 2
From: Caguas, PR
A/c issue
Though I would not consider my A/C an award winner, it had been working ever since I purchased the vehicle back in '96. Recently, it developed a weird problem where placing the Fan Selector in 1 or 2 works good. If I turn the vehicle on with the Fan Selector in 4 it also does work great. Now, if I move the selector to 3 at any time, the 10amp fuse blows. The issue is that sometimes it burns right away and sometimes it burns a few minutes later... All the issue is at 3. I am not sure if it is the selector or the Blower Motor Resistor.
I need some help from more experienced troubleshooters... TIA
I need some help from more experienced troubleshooters... TIA
Senior Member
Joined: Jan 2005
Posts: 397
solrac3:
Disclaimer - I'm looking at a circuit diagram for the '99 - I assume there were no major changes in the heater set-up but can't guarantee.
Your symptom is confusing. Does this happen only when the A/C is selected or all the time? This could be important.
Most often the resistor pack is the culprit for blower related issues - but in this case I'm not so sure. The current that flows through the resistor pack and blower motor is protected by a different fuse - 25 AMP
The 10AMP fuse your're blowing is just for the blower relay (plus rear window defogger and headlamp washers) and the A/C control module (thus the question above) This fuse is not connected with the resistor pack or motor. Relay coils just don't short out inside metal relay cans, and in any case, the relay has no idea which setting your fan switch is on. So why does it only happen on 3?
Well, the hot wire for the A/C control module goes from this fuse through a separate contact set that is located inside the fan speed switch. This is the only area where current flowing through the 10AMP fuse comes even close to something that is speed dependent.
So there seem to be two possibilities - both pretty rare I'd guess
1) Something has gone wrong with the speed switch and in position 3 there is eventual contact between the blower motor section of the switch and the hot wire going to the module, thus blowing the fuse., or.
2) Something is happening in the resistor pack that causes too much current to flow through the switch (only on #3), which eventually gets hot and casues condition 1 above.
So I suspect the fan speed switch, but it's easy and cheap to try another resistor pack if you don't want dig into the control panel first. If that doesn't make any difference I'd replace the switch.
If I think of any good ways to isolate one part or the other I'll let you know.
Ron
Hope this helps.
Disclaimer - I'm looking at a circuit diagram for the '99 - I assume there were no major changes in the heater set-up but can't guarantee.
Your symptom is confusing. Does this happen only when the A/C is selected or all the time? This could be important.
Most often the resistor pack is the culprit for blower related issues - but in this case I'm not so sure. The current that flows through the resistor pack and blower motor is protected by a different fuse - 25 AMP
The 10AMP fuse your're blowing is just for the blower relay (plus rear window defogger and headlamp washers) and the A/C control module (thus the question above) This fuse is not connected with the resistor pack or motor. Relay coils just don't short out inside metal relay cans, and in any case, the relay has no idea which setting your fan switch is on. So why does it only happen on 3?
Well, the hot wire for the A/C control module goes from this fuse through a separate contact set that is located inside the fan speed switch. This is the only area where current flowing through the 10AMP fuse comes even close to something that is speed dependent.
So there seem to be two possibilities - both pretty rare I'd guess
1) Something has gone wrong with the speed switch and in position 3 there is eventual contact between the blower motor section of the switch and the hot wire going to the module, thus blowing the fuse., or.
2) Something is happening in the resistor pack that causes too much current to flow through the switch (only on #3), which eventually gets hot and casues condition 1 above.
So I suspect the fan speed switch, but it's easy and cheap to try another resistor pack if you don't want dig into the control panel first. If that doesn't make any difference I'd replace the switch.
If I think of any good ways to isolate one part or the other I'll let you know.
Ron
Hope this helps.
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