Rear auxiliary heater switch turns choke light on?

BrandonMc · July 20, 2019, 12:31 PM

What's odd is that when the wires are connected to the rear auxiliary heater, when i turn the aux heater switch to any position, the choke light immediately comes on. The brand new aux heater motor does not run, but will flick a little with movement - I do have voltage back there. There's a resistor wire set that could possibly not be working? But they're quite robust wires so ?

Do you think the aux heater switch could be bad? Almost finished fixing these electrical issues.

Rickf1985 · July 20, 2019, 02:21 PM

Something is backfeeding the choke circuit from that heater blower switch. The choke light is also on the ignition circuit if I remember correctly so you really need to track that down or you could end up with a no shut down situation. Disconnect the power out wire from the back of the switch and then turn it on and see if the light still comes on. How many wires off the switch? Not including the main power in wire. I am asking these questions instead of looking at the diagram just in case someone has modified something.

BrandonMc · July 20, 2019, 05:08 PM

Do you think this resistor component at the aux heater is possibly blown? I don't see how but possible. The choke light does not come on when the 4-wire electrical connection is removed from the aux blower motor.

You know, it's funny you mention a no shut off situation. Before all these electrical mishaps occurred, there was indeed a no shut-off situation when the key was removed until turning the headlamp switch off.

For anyone needing an aux blower switch, this one seems like a direct replacement: Four Seasons 35702 Switch

Rickf1985 · July 21, 2019, 09:31 AM

The resistor is very simple, if it is burned out you will only have high blower and that is it. It is exactly the same as a light bulb. Those coils you see are the resistors for each speed and they are in series so if one burns out you lose both medium and low speed. And think of the resistors just like the filament of a light bulb. It sounds to me like you have a ground issue up at the dash area in relation to that switch harness. You say you have a 4 wire harness, again I am going without the diagram since I am on my way out the door but I am thinking you need three wires for the blower so the last is the ground returning back up front. I have to run some errands before it gets too hot, (it is already 92 and 105 heat index at 09:30!). As soon as I get back I will dig into the diagrams and get back to you.

Rickf1985 · July 21, 2019, 12:38 PM

Brandon, I got into the diagrams but it is going to be really tough to do this bit by bit on a forum. Can you PM me a phone number so we can talk in real time?

DVan · July 21, 2019, 11:22 PM

Also, a common reason these resistors "blow" or burn out, is rodents or other critters building nests in or near them. The resistors get VERY hot and without good airflow they burn up. Not that RVs ever sit long enough to attract unwanted guests. W%

Make sure any nests are cleared out.

BrandonMc · July 22, 2019, 08:21 PM

okay, so today I got a 12v 1000mA plug in wall transformer and put the bare wires together, and the fan runs just fine. The wires from the dash switch to the back of the coach indicate 12v, but I'd imagine just like other parts of the wiring, there's a bad connection or because the wire got toasted enough that its resistance is way up.

need to trace down the wiring from the front to the back. It'll be a

to rewire the blower motor from front to back underneath the coach. But I've been through worse it seems. I'll let ya'll know what I find.

Rickf1985 · July 23, 2019, 10:05 AM

That plug in transformer is only 1 amp and the fan needs at least 5-6 amps so that alone will raise the resistance on the wires. How are you reading the resistance? You need to unplug the fan and unplug the switch and then read the resistance between those points. Since the distance would make that pretty hard what you need to do is make a jumper to go between two of the wires on one end or the other and then measure the resistance between the ends at the plug with the open ends. This will give you total resistance between the two wires. Do this for all combinations of wires and if the readings are all the same then the wires are probably good. If you are trying to read resistance with the fan plugged in then you are also reading the resistance of the fan motor plus the resistance of the resistor for the two lower speeds.

Rickf1985 · July 23, 2019, 10:08 AM

By the way, In your signature you list you set up as a 87 coach and a 88 chassis. You have to have that backwards since they could not have built the couch on a chassis that was not built yet. The chassis is almost always a year earlier than the coach.

BrandonMc · July 24, 2019, 12:06 AM

Quote from: Rickf1985 on July 23, 2019, 10:08 AM
By the way, In your signature you list you set up as a 87 coach and a 88 chassis. You have to have that backwards since they could not have built the couch on a chassis that was not built yet. The chassis is almost always a year earlier than the coach.

well, that's as I've known it for many years and how it was sold as. As in, a new year vehicle is sold as 2020 in 2019. I dunno, maybe you could be right but I believe the body is an 87 on an 88? i?? build date is in september 87. vin check shows 88 chassis.

BrandonMc · July 29, 2019, 09:43 AM

Okay, So I moved the rear wipers and aux heater to the ACC slot instead of IGN. The wiring diagram shows IGN as a source in the fuse block, but ACC seems to work just great. I'm also moving the mains power "KE" to the ACC side. Now everything works as it aught to, and the check engine light now works as well. Choke light also works fine now.

Thought I'd update this so anyone having similar issues can see how the problem was solved.

Rickf1985 · August 11, 2019, 08:41 PM

"Technically" that would mean that those items would ONLY work when the switch was in accessory. But if it is all working then leave it alone but be sure to make note of it in your manual what you did so if this pops up later you have a record of it. I am curious, did you ever change the ignition switch? Or does it look like anyone may have modified the wiring for the switch?

BrandonMc · August 12, 2019, 03:15 PM

Quote from: Rickf1985 on August 11, 2019, 08:41 PM
"Technically" that would mean that those items would ONLY work when the switch was in accessory. But if it is all working then leave it alone but be sure to make note of it in your manual what you did so if this pops up later you have a record of it. I am curious, did you ever change the ignition switch? Or does it look like anyone may have modified the wiring for the switch?

The wiring on that one remains stock, unless someone else modified it. I did in-fact replace the ignition switch at one point sorting through some issues I was having previously.

So far so good! One trip taken last week, and all was well.