Here's what I got;
1997 International 4900, DT466, A/C, 7 speed, (if any of this matters).

I've lost the hi speed setting on my heater and A/C blower motor. Off, low and medium still work fine but nothing on hi speed.

I checked the auto-reset circuit breaker and that's fine, power to the feed side of the circuit breaker.

I have power to the speed setting switch on the dash board.

When the switch is set to low or medium, I have power at the black wire on the blower motor, tested with a test light. (There are only 2 wires going into the blower motor; black and white. I assume white is ground)

When the switch is set to high I have no power in the black wire at the blower motor, but I DO have power at the relay behind the dash on the passenger side.

If I attach a positive powered jumper wire to the black wire at the blower motor with the switch set to high, I get the high speed operation of the blower motor.

If I attach a positive powered jumper wire to the black wire at the blower motor with the switch set to off, I get a high pitched whine from the relay and NO operation of the blower motor.

There are 3 relays behind the dash that are all the same style, one for the heated mirrors and 2 for the A/C. I can switch them all around, (to test if they're ok or not), and they all do the same thing; no high speed.

So my conclusion is that somewhere between the relays and the blower motor I'm losing the power. Where does the power GO after it leaves the relay and before it reaches the blower motor? Is there another relay somewhere? ANY suggestions?

Thanks!

chaikwa.

 

Sounds to me like it is the either the switch or the replay, try swapping them around and see what happens. I would assume that the wires go right from the relay to the motor, but who knows. Also if it is only a 2 wire motor there is probably a resistor type setup on the supply side of the motor to setup the two speeds, which tends to go bad also.

 

not sure on 97, however

from the switch, the wiring goes to a resistor, usually within the blower box, for cooling purposes. you need to find that resistor, and it should be the culprit in this case. On the older ones, the resistor was located near/above the passenger side footwell, facing the seat. Could be behind the glovebox.

Try that and see what you find

 

This is too funny! I jut this week had an International in my shop for this very thing! I am not an International guy by any means but the AC systems and blower motor circuits are about the same all around.

The blower motors usually revcieve a full 12 volts on high so they dont go through the resistor. I did however notice that international uses an odd resistor with three coils and something else attached. It may be your culprit but I doubt it.

Does the blower motor kick on even for just a split second when switched to high?

 

It is your fan speed switch, it is a common failure. If the resistor goes then you only have high fan speed. I have changed numerous switch's on our intertrashionals. Also pull the plastic panel on the passenger side that covers the climate control systems, there is a metal mesh screen on the lower left side of the ducting, (by the coils) pull it out and clean it, you will be amazed at what your gonna find on that screen.

Any questions call me


Tim

 

Thanks EVERYONE for your replies!!!! And especially to Tim. It means a lot to me that you'd go so far to call me to help me resolve this problem!

A switch has been ordered and will be in at the Intertrashional dealership first thing in the AM. I'll let y'all know how I make out tomorrow after I change out the switch. I ordered a relay too, just so I'll have it. The dealership parts department said they don't sell many of them so that might not be the problem. But if it IS, I'll have one anyway!

Thanks again everyone, I appreciate you taking the time to reply!

chaikwa.

 

Well, I pulled the dash apart and replaced the switch today... made no difference, still no high. Started looking for something else that would be causing the problem. Checked the resistor and it tested out ok. Then I noticed that when I placed a test light in the main wire from the switch to the motor and turned the switch to high, I got a momentary spurt of low level power. Started tracing that wire that feeds the switch and ended up at the fuse panel on the drivers side. Same problem there; good power there until I turned the switch on to high, then nothing. Found that the wire was corroded and connected to the fuse terminal by only one or two strands of wire... not enough to support the draw of the motor. Replaced the wire and now the motor works like brand new!

Good thing I replaced the switch anyway tho, it looked like it had gotten wet at some point and the terminals were all rusty and green.

Thanks again to everyone that responded!

chaikwa.

 

My only other suggestion was going to be to look at one of the two plugs behind the plastic cover for the climate control, they like to corrode their also causing the same problem, The switch and the aforementioned plug are the usual suspects for that type of blower failure. Since you found corrosion at the fuse block, this next question comes to mind, does your dome light work?

What do I owe you for the switch?


Tim

 

First of all, you don't owe me anything for the switch. I asked for advise, not a guaranty! And secondly, if I'da known what kinda condition the old switch was in, I'da changed it anyway. I'm of the opinion that corrosion makes resistance, resistance makes heat and heat makes fires. Fire ain't a good thing when it's in MY truck!

As for the dome light; it don't have one! It has door jamb lights that amount to nothing more than step and tow bumper license plate lights; round housings with half-moon shaped lenses. Drivers side works, passenger side don't.

Weird interior on this truck; pleated leather headliner and door coverings, A/C, 4 speaker stereo system, carpeting, heated mirrors, cruise control but no interior lighting, intermittent wipers or power windows.

You were right about that filter/screen thing Tim, what a MESS! It looked like a giant blue Scotch pad. Pulled it out and soaked it in hot water and soap for about an hour before all the gunk would loosen up. Air flow is a LOT better now. Maybe with proper air flow going accross the coil now, the compressor won't cycle as much! Blew out everything in that air box with compressed air and filled the passenger side floor with junk.

Next project; lighter springs on all four corners so it rides more like a truck instead of a buckboard! According to the spring shop I have the heaviest springs available for that series truck. I'd cut all but 3 or 4 leafs with my portable bandsaw but I ain't got that brave yet!

chaikwa.

 

Cool, I am glad it worked out for you. The reason I asked about the dome light is that behind the fuse panel their are multiple plugs that control various functions, if you had a green corroded wire for the fan blower back there then that means water is getting there, (very common), also affecting the other plugs, one of which is the dome light, thats the one that is usually affected first.

JFYI, there is most likely wiring and a cut out already in the cealing for a dome light. I add the large bright round ones in our flatbeds for the drivers so they can see at night.

I know you are gonna be taking some big road trips with that truck, if you have any problems give a call, regardless of the time, I have done MANY a road side repair on them and would be happy to help. You would be surprised what and how easy it is to fix some problems on the road yourself.


Tim