Testing blower resistor block

[dpuckett]

I THOUGHT I had found this section in my 93 FSM, but after buying a multimeter, it has suddenly disappeared from the pages of the book. Is there a way to test the resistor block, and what values do I need to find on what tests? Or is it just in a section I didnt think to read through? There are all kinds of "Check the Obvious" flow charts for noise and vibration, but nothing for low speed, other than check resistor block. Then nothing on how to go about checking it.



Daniel

 

[TWorline]

Daniel:

It looks like all you have to do is check the continuity of the resistors, if you find one that is open it is bad. Check all of your wires going into your plug to see if any of connectors have backed out of the housing.

 

[bmoeller]

I assume you checked the fan switch? That has been the culprit for me before.

 

[MMiller]

Using your OHM setting, test the resistors for the fan speed. Low will offer the most resistance, and less resistance each speed until high. High speed should net almost no resistance, and the fan should get 12 volts. You probably already knew that though.



Are you fighting the fan that doesn't put out much air flow? We discussed it a little at SOP.



Michael

 

[dpuckett]

Yup, same fan in the same truck. Other truck flows even less, i. e. I dont think it would pass inspection. Fortunately it has been warm and dry enough lately to not need the defrost on high, or truly high.



bmoeller- havent tried the switch just yet. I am lining up ideas of what is likely. I think the switch may be getting bad in the 90, as it wont hardly come on.



Daniel

 

[TWorline]

Daniel:



Try connecting 12volts directly to the fan from your battery bypassing the block and see if if churns any better. The resistor block is only for the lower settings, maybe your fan is not getting a true 12 volts to it or not enough amperage due to corroded wires/connectors.

 

[PToombs]

Could the heater core be plugged? I had an '89 that had a mouse nest in the air way to the core. The airbox was plugged solid. I pulled it out and vacuumed all I could out. I even pulled the fan and blew back with a compressor. Might be leaves or something. Use a mirror and look.

 

[dpuckett]

Whole thing is clean- checked that when troubleshooting the AC. The temp coming out is plenty warm, just cant feel it from more than a foot away from the vent.



DP

 

[dpuckett]

Update

Tested the voltage at the plug in with my meter (that thing is so neat), and the 92 has 7. 5 volts on high. 90 has 2. 5. So, which do I need, resistor or switch? I'm thinking resistor block.



DP

 

[PToombs]

Did you try 12 vts direct like Tim said? I would make sure you have 12v going in, you should have 12v going out. The switch should put out 12v on all terminals, going to the resister block. My switch was getting hot and smelled. I took it out and disassembled it and cleaned the contacts. Then I put dislexic grease on it and put it back together, greased the terminals too. Oh, I had to use a hammer and punch to tighten the rivets a little. It works good now.

 

[dpuckett]

DIrect 12V sped the blower up a bit. ALL the lines should have 12V coming out of them? interesting... ...



DP

 

[MMiller]

DIrect 12V sped the blower up a bit. ALL the lines should have 12V coming out of them? interesting... ...



DP

I don't exactly know how the switch is wired, but the wire that powers the fan up, will NOT have 12 volts on low, and med speeds, it will only have 12 volts on high. Voltage to the fan, controls the speed.



Michael

 

[B.G. Smith]

If you are not completely confused by now this should do it. The switch is just a moulti- position switch as stated above, all positions should produce 12 volts to the resistor. The resistor block has several resistors and a direct position for high speed. The various resistors provide various voltage values for different fan speeds. And yes, you are welcome. bg

 

[dpuckett]

B. G. Smith- not confused yet. I had come to that conclusion, though hadnt seen it phrased that succinctly.



MMiller- re-read post #9- 7. 5 volts was on HIGH. :-laf Didnt test any others, as they are plenty slow as it is.



DP

 

[PToombs]

BG,thanks, thats what I was trying to say.

DP, did you check volts going in?

And if you check post#10, I said I had my switch all apart, simple switch.

Run a piece of baler WIRE from the battery to the fan, hayseed! :-laf :-laf

 

[dpuckett]

I cant run baling wire to the fan from the battery- it'll short out the battery. Besides, my exhaust system would fall off.



It's been 65-70 deg lately, so I have been running the 2-70 A/C.



DP

 

[PToombs]

I cant run baling wire to the fan from the battery- it'll short out the battery. Besides, my exhaust system would fall off.



DP

:-laf :-laf