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peterpete190
peterpete190, Auto Technician
Category: RV
Satisfied Customers: 24656
Experience:  Over 17 years diagnosing and repairing various model vehicles.
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1994 Damon motorhome. Wynns Frostemp hvac system. Three

Customer Question

1994 Damon motorhome. Wynns Frostemp hvac system. Three lower fan speeds work, high speed doesn't. Relays are good, replaced blower switch, same result. Bad diode on resister pack board? Can only find one fuse on fuse block for heater, it's good.
Submitted: 12 months ago.
Category: RV
Expert:  peterpete190 replied 12 months ago.

My name is ***** ***** I am a professional here at Just Answer. I noticed that your question had not received a response and thought I would see if you still need help with this.I apologize for the delay and I hope I can still assist you with this here.My info is somewhat limited on your model here but I had seen no one else has responded and would like to see if I can help here.If at any time you feel that I cannot help with this please let me know.

Some models all speeds for the blower run through the resistor.Usually the high speed is just a circuit that runs through the resistor that isnt controlled by the resistor but the circuit can fail on the resistor to where the resistor needs replaced to correct this fault.I dont have the exact diagram info on this model here but this sounds to be the cause here.I have seen the resistor pack fail before needing replaced.This would have to be tested further to be sure.

If more help is needed, use the reply tab to continue our conversation. If no further assistance is needed, kindly rate my service.You can rate at any time and we can continue to work on your question as this will not close out your question.Keep in mind in some cases it can be difficult to fully diagnose or help repair your vehicle without seeing it and I work on delivering the best possible answer from what I see to work with.

Thanks Pete

Customer: replied 12 months ago.
Hi Pete. This is Steve. Not having a circuit diagram I traced the conductors from the switch to the resistor pack. Took out the resistor pack, none of the coils are open ( that's why the three low speeds work apparently) the high speed conductor is orange off the switch and runs into a relay on the firewall, swapped that relay with the one below it and still got no high speed. The conductor to the high speed plug is orange with black stripes, that comes out of the relay to the high speed bayonet on the resistor block. There is a diode on that path that showed higher resistance one way than the other so it seems to be gating. Can't read the value on it but it does seem a bit heat corroded. Thought maybe there was another supply path to the high speed circuit with a blown fuse but there doesn't seem to be. Thought about jumping the diode but am afraid of unintended consequences. Writing focused my mind a bit, maybe I should test to see if there is voltage off that high speed path with the switch on high.
Expert:  peterpete190 replied 12 months ago.

One common component to fail and cause the no high speed on the set up that uses a high speed relay is a faulty blower control switch.I have seen the high output circuit melt at the connection to the switch with the switch and connector both needing replaced.If this has not been checked this needs done.

Thanks Pete

Customer: replied 12 months ago.
The blower control switch has been replaced with a new one and the connector is ok. No change.
Expert:  peterpete190 replied 12 months ago.

Unfortunately with my info being limited on this model here I will have to open your question up for others to see if they can assist further on this.I hope you can get this resolved with ease.

Thanks. Pete