Fixed climate control blower speed control

[Forest Grump]

No high speed for blower motor, 3 lower speeds worked. Ruminated for months, googled circuit diagrams etc. replaced blower relay, no good. From my reading I learned it was not uncommon for the high speed to bypass the blower resister. So after replacing the relay, I decided it was probably for the high speed and had a 12 g wire with a black stripe. Started checking fuses, big ones. Those in the chassis were fine. Started checking on the firewall and low and behold there was a single large fuse holder which was damaged with 12 g red wires and a black stripe and a damaged 30 A blade fuse. Cut it out, went to napa, got a new fuse holder for $2 and installed it with a new fuse.

It worked. We now have all 4 blower speeds including high speed. It is located to the right of the battery kill switch coming out of a wiring harness with a bracket to secure it to the firewall with a single screw.

[RexAir_3650]

I noticed your post on fixing the blower motor high speed issue. I have the reverse problem with the 3 lower speeds not working. I replaced the blower motor and the blower resister so far. (About every post pointed to the blower resister pack so I thought I had it nailed. NOPE) It did work for a while intermittantly but never solid now it doesn't work at all. I am scratching my head a little and must be missing something on the lower speeds as far as understanding a possible diagram. Anyway I do not have a wiring schematic so any help would be appreciated in understanding what parts do what. The way I understand this is that there is a fuse, power relay, the fan switch, the blower resister, and the motor.

I am wondering if possibly the blower motor relay could be my problem or is this just for the high speed? It works like a charm on high at all times. I have a 1999 Rexhall Rexair on a Ford chasis with the v10 triton. (Trying to give you as much information as I can.)

[ottffss]

Evans-Tempcon?

Evans Tempcon, Inc

The blower relay "block" can be quite complex. For example, mine has 7 relays and a handful of fuses just to control fan speed - in addition to the blower resistor packs.

[Forest Grump]

High speed only definitely suggests it is the resistor that has burned out. The relay I think is just for high speed as is the 30 amp fuse. The fact that high speed works suggests that the two are working properly. It sounds like once you changed out the resistor the fan did work for a short time, this suggests that it was the relay. Some of the relays available are pretty cheap. See if you can find a motor craft part or a high end replacement. The other thing it might be is the switch itself. If you know how to use a multimeter you can check your switch and resistor.

If it was mine I would replace the resistor again with a high quality part and then check out the switch. If the switch did burn out it should have an odor or other physical evidence. Check the resistor for evidence of failure. There is a a heat resistor on the back which blows after a specific high temperature is reached. You can test this too with a multimeter. Good luck!

[subford]

As far as I know if you have a EVENS system you only have one relay and if it works on high the relay is OK. The relay is in the relay/fuse panel in front of the radiator.

Here is a diagram of an Evens system and how it hook up to the F53:


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[Forest Grump]

From the above circuit the blower relay provides power for all speeds of the fan just not high speed.

[Hikerdogs]

Quote:

Originally Posted by Forest Grump No high speed for blower motor, 3 lower speeds worked. Ruminated for months, googled circuit diagrams etc. replaced blower relay, no good. From my reading I learned it was not uncommon for the high speed to bypass the blower resister. So after replacing the relay, I decided it was probably for the high speed and had a 12 g wire with a black stripe. Started checking fuses, big ones. Those in the chassis were fine. Started checking on the firewall and low and behold there was a single large fuse holder which was damaged with 12 g red wires and a black stripe and a damaged 30 A blade fuse. Cut it out, went to napa, got a new fuse holder for $2 and installed it with a new fuse. It worked. We now have all 4 blower speeds including high speed. It is located to the right of the battery kill switch coming out of a wiring harness with a bracket to secure it to the firewall with a single screw.

This was a common problem for many GM vehicles of past years. The new fuse and holder may be only a temporary cure. In most cases the real culprit is a bad ground from the motor casing to the frame or grounding lug. As the ground deteriorates it creates high resistance. The fan motor draws higher and higher amperage as the ground gets worse.

In most cases the fuse and wiring will handle only 80% of the rated load for extended periods without overheating. As you near the load rating the plastic fuse holder and wiring insulation start to melt. Over time they deteriorate to the point connnectivity is lost. I'll bet if you look closely at the old fuse and holder you'll find the fuse is still good but the housing is so deteriorated the wire has lost contact with the end of the fuse.

[RexAir_3650]

Thanks for posting the schematic this really helped me out. After looking this over the only two things that control the blower speed would be the blower resister or the fan speed switch. The blower resister seems to be fine after testing it. I did wiggle the wiring harness where it attaches to the switch by reaching up under the dash and it worked for a minute on medium speed but only once. I believe I may have a defective switch. I will let you know once I pull it from the dash and test it. I probably won't have a chance this week since I am driving the RV across AZ to CA. But I will reply once I get the testing done with the results. But looking at the diagram it seems to be the culprit. If it is the culprit the other problem will be trying to figure out a work around for replacing the switch since the switch seems to be built into a three switch block. (One switch for the fan speeds, One switch for AC/VENT etc.., one for cold/hot air mix) Possibly might find one at a wrecking yard but going to be fun if it is the fan speed switch. Anyway I will post with the results in a week or so.

[Forest Grump]

BTW my fix was for the Ford F53 chassis which uses Chrysler parts. The switch when pulled out should be separate from the other switches.

[subford]

What year F53 used Chrysler parts?

[Forest Grump]

Mine is a 1991.

[RexAir_3650]

Quote:

Originally Posted by RexAir_3650 Thanks for posting the schematic this really helped me out. After looking this over the only two things that control the blower speed would be the blower resister or the fan speed switch. The blower resister seems to be fine after testing it. I did wiggle the wiring harness where it attaches to the switch by reaching up under the dash and it worked for a minute on medium speed but only once. I believe I may have a defective switch. I will let you know once I pull it from the dash and test it. I probably won't have a chance this week since I am driving the RV across AZ to CA. But I will reply once I get the testing done with the results. But looking at the diagram it seems to be the culprit. If it is the culprit the other problem will be trying to figure out a work around for replacing the switch since the switch seems to be built into a three switch block. (One switch for the fan speeds, One switch for AC/VENT etc.., one for cold/hot air mix) Possibly might find one at a wrecking yard but going to be fun if it is the fan speed switch. Anyway I will post with the results in a week or so.

I disassembled the dash/removed the control panel and found out the switch is discrete so I was able to remove it from the panel. I tested the switch and it seems to be bad. I searched online and found an exact replacement. It is an Indak S9103L. A long shaft 5 blade A/C Fan switch is the description. Hopefully this will fix the problem. I will update again when I get the new switch installed and test the fan speeds.

[RexAir_3650]

I received the new switch, tested it and my old switch did have a problem. I thought great. But I just installed it with no luck. At this point after replacing the switch, resister block, and the fan motor I guess I will go back and test the resister block to see if the new one somehow went bad. Maybe the bad switch caused it to go bad? It did run for a little while and somebody suggested that the resister block could have went bad again even though it was brand new. Does anyone know how many ohms the resisters should read with a meter? I tested the resister block and I see what looks like an open on the silver resister. But nothing looks burnt visually. I see a little discoloration on some of the coiled resisters but that would seem normal. Anyway does somebody know what the value of the silver resister should be or is this something else besides a resister? The new part I am testing is marked a Motorcraft and is listed as a Muenster 2G927 or a 035-00006 by SCS Frigette. Below is the link to it and it has a picture of the resister block. http://scsfrigette.com/pdfs/rv/Relay...20Breakers.pdf Also does anyone know if this part is available at an auto parts store? My new one is marked Motorcraft which the old was not. So if it is a Ford part like an F53 chasis part it seems like it should be available at a normal parts store.

[Bbspinstl]

I had a similar situation on my 2007 F53 chassis fan blower where the 3 lower speeds did not work but the highest speed worked fine. My system only had three main parts The speed switch the resistor network and a fan speed relay. The relay turned out to be at fault and replacing it fixed the fan speed problem.