Electrical Testing Help Please

[Kazoo Tom]

I have had a problem with the dash heater-a/c fan not working at all speeds. I can turn the control all the way to high and only get a very low fan speed. I have listened to the fan and do not hear it changing speeds at all until I can finally hear it on high.

I have learned that the problem might be the fan switch, and/or a diode pack located under the hood on the heater core box.

I have a small multimeter and guess that I can test the switch by seeing if I get different voltages depending on the switch position.

My real question is what is the procedure for testing the diode pack?

Any instruction would be greatly appreciated.

[Kazoo Tom]

I have had a problem with the dash heater-a/c fan not working at all speeds. I can turn the control all the way to high and only get a very low fan speed. I have listened to the fan and do not hear it changing speeds at all until I can finally hear it on high.

I have learned that the problem might be the fan switch, and/or a diode pack located under the hood on the heater core box.

I have a small multimeter and guess that I can test the switch by seeing if I get different voltages depending on the switch position.

My real question is what is the procedure for testing the diode pack?

Any instruction would be greatly appreciated.

[Hitchhiker]

Hey Tom,

In simple terms, a diode will read continuity in one direction only. To test, read one way then reverse the probes and read the other. If it's a diode pack the same theory will apply but you may have to figure out how the diodes are configured in the pack.

[Kazoo Tom]

I mistakenly stated "diode" pack when in actuality it is a "resistor" pack. Can I blame the confusion on age?

I am told that the resistor pack my have a fuse embedded in it that might be blown, but cannot be replaced individually.

[Hitchhiker]

OK, it's a resister pack. That just makes it easier to test.

The lead or lug that went to the highest fan speed should read the lowest resistance. Actually, that one is probably zero resistance (or negligible) to allow the most current to pass.

The low speed should read the highest and so on. If it's fused and the fuse is blown, then it'll read an infinite amount of resistance on the lugs that are fused.

Hope this helps.

[RV Wizard]

I will bet that you will find a bad fan speed resistor that is mounted in the blower housing on the firewall of the coach. It is real easy to change out. Mark you wiring if you need and remove the old. When you do you will probably be able to see that it is burned out in an area or two. Buy a replacement at an auto parts store and reinstall. Your done.

[Kazoo Tom]

Thank you all for your answers. I believe that it is the resistor pack. I have located the pack and will remove it this weekend and see if I can find a replacement at the local auto parts store. Hope it works, but then I am not always lucky when it comes to the simple fixes.

[NeilV]

<BLOCKQUOTE class="ip-ubbcode-quote"><div class="ip-ubbcode-quote-title">quote:</div><div class="ip-ubbcode-quote-content">Originally posted by Kazoo Tom:
Thank you all for your answers. I believe that it is the resistor pack. I have located the pack and will remove it this weekend and see if I can find a replacement at the local auto parts store. Hope it works, but then I am not always lucky when it comes to the simple fixes. </div></BLOCKQUOTE>

Tom,

On your 98 it could be either the switch or the resistor pack. The resistors are usually the open wire type and are in the blower housing to cool them. It would be a good idea to inspect the housing for anything that would impeed airflow and cause them to overheat/fail while you are in there. I have seen them glowing cherry red when installed outside the blower housing by someone who did not get an exact match and did some creative mounting. The dash switch will most often be visibly scorched or chared if it is failing and is pretty easy to troubleshoot visually or with a continuity tester.

Regards,

Neil

[Kazoo Tom]

Neil,

I have checked the back of the switch - easy to get to in a Winnebago. Everything seems tightly connected and no evidence of scorching or any other abnormality. I will be removing the resistor pack this weekend and working from that end. Wish me luck

[spaccman]

I have the exact same problem on a 2000 winnebago Brave. The lower speed settings NEVER worked, just the highest setting. Now even that doesn't work so I am in Phoenix with no dash AC. If you manage to fix the blower successfully please email me the results at paccia@mindspring.com or post it on this page......-THANKS -spaccman

[Robert & Kiki]

I had only High air working and no other speeds. Changing the RELAY fixed it. I now have all speeds. It's a Bosch relay & is next to resistor pack on firewall, picked one up at NAPA. Only $11. One or the other should fix the problem.

[Kazoo Tom]

Spaccman,

I first changed the resistor pack (by the looks of it, it was needed) which resulted in only a high speed. I then changed the relay and now everything is fine. You can change both for under $30. I got the resistor pack through Lichtsinn Motors as I could not find it through any local auto parts store. (Lichtsinn)

You can call or email their parts dept. They have been very helpful for me, and their prices are less than I found elsewhere. The relay is available at any auto parts store. Take the old one in with you to make sure the plug matches up.

Those items have my blower working just like new. Simple repair - I can send you a pick of the parts if you need them. Pictures are at the beginning of the thread (here)