Strange Happenings with new Dash A/C Blower Motor

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Strange Happenings with new Dash A/C Blower Motor

August 04, 2011, 05:13:21 pm

I just installed a new dash air blower motor because my old one occasionally made a squealing bearing noise. On my trip today from Oklahoma to Texas I noticed that my dash volt meter was showing less than 12 volts. I stopped and check the voltage at the alternator and the starting battery with my digital volt meter. Both were OK, 13.7 V at the battery and 15.3 at the alternator.

I decided it was a gauge issue and drove on. I noticed that at higher rpms the voltage dropped and then the voltage came back to near normal at idling rpms. I thought it was probably a slipping belt but I checked that too. When Peggy revved up the engine there was not sign of slippage or jumpy belts. Belt tension seems OK. So its probably not a belt or an alternator problem.

Then about an hour ago, the "Check Transmission" light and alarm started to occasionally go off. I pulled over immediately and Bill Chaplin helped me find the toggle switches and lights to check for a transmission code. I called my OKC Detroit/Allison shop. We checked for codes but there were none for the trans or the engine so we decided that the problems were more electrical. I checked under the dash for any loose or corroded connections and found none.

As we got settled at the Oasis RV Park in Amarillo I noticed that when I turned off the dash A/C blower in about 10 seconds the dash volt meter went back to normal. I thought that I had a bad "New" blower motor so I pulled it out and went to Orielly to get another one. I installed it and it too causes the dash volt meter to drop to around 12V with the engine running and the A/C blower on high. When I lower the blower speed the voltage starts to increase but not above 13V until I turn the blower off.

I know this is a lot of info but I figure if anyone can help me figure this one out they will need all of the above.

HELP!!!

Re: Strange Happenings with new Dash A/C Blower Motor

Reply #1 – August 04, 2011, 05:34:19 pm

Based on your description, I would conclude that the voltmeter is on a circuit sharing a supply wire with the blower motor. The wiring for the blower is less than adequate. When the blower is operating, there is significant voltage drop from the source (alternator/battery) to the blower and voltmeter. The voltmeter probably has very heavy damping, causing it to react very slowly to changes in voltage.

A remedy is to provide a separate, possibly dedicated, circuit for the blower motor. The size of the wire, and associated fuse or breaker, will be determined primarily by the maximum current drawn by the blower motor. The length of the wire from the voltage source to the blower will also be a factor. The longer is the distance, the larger the wire should be.

Perhaps someone with more specific experience can recommend appropriate wire size, fuse size, and a connection point for a source.

Poor grounding can cause the same problems. All current flowing to the blower must find an adequate path to complete the circuit.

Re: Strange Happenings with new Dash A/C Blower Motor

Reply #2 – August 04, 2011, 05:53:10 pm

JD, your conclusion is basically the same one I came to. But, my question is why didn't the original motor do the same thing. I almost brought it with me and now wish I had. I'm leaning toward going to NAPA and try one of their motors. This one is Chinese and was only $28. I guess I could even try one from a GM dealer.

Re: Strange Happenings with new Dash A/C Blower Motor

Reply #3 – August 04, 2011, 06:21:38 pm

This sounds a lot like my symptoms when my dash solenoid was going bad. With the fan off, everything was fine. With the fan on high, all of my gauges and the fan would shut off. With the fan on medium, everything would work until I make a left turn, and everything would shut off for about ten seconds, and then come back on.

oldMattB

Re: Strange Happenings with new Dash A/C Blower Motor

Reply #4 – August 04, 2011, 06:42:21 pm

OK Matt, I am now intrigued. What is a Dash Solenoid? Where is it and where do I get one if I need it?

Re: Strange Happenings with new Dash A/C Blower Motor

Reply #5 – August 04, 2011, 09:08:53 pm

Kent,
My coach is 2 years older and I have seen the same thing but not so bad that the transmission had problems. I did change my solenoid and it helped significantly but there still seems to be more resistance somewhere else that I haven't traced down yet. The solenoid looks just like the boost solenoid and is bolted to the "floor" of the wiring compartment(under the dash) right in-line with the steering wheel. There will be many wires (big and small) attached to the main terminals. It makes a thunk noise when you turn on the ignition. Most difficult part is getting the nut on each terminal with all the wires. I recommend disconnecting the batteries so you don't accidentally short something. As a check of your existing solenoid you can measure the voltage across the main terminals(with main engine and a/c blower running) - I not sure what the max. drop is you should see but I would think anything over a volt would be cause to change it.
I'm starting think the remainder of my problem is just all the old connections (including the crimp connection on each connector) adding up over many connections. No one thing seems to be the smoking gun.

I suspect the new motor you bought is not the same quality and it pulls more juice due to inferior materials and/or craftsmanship.

Re: Strange Happenings with new Dash A/C Blower Motor

Reply #6 – August 04, 2011, 09:21:26 pm

Quote from: Kent Speers – August 04, 2011, 06:42:21 pm

OK Matt, I am now intrigued. What is a Dash Solenoid? Where is it and where do I get one if I need it?

Also called ignition solenoid (not starter solenoid). Under dash. It feeds all circuits that are hot when the ignition is on. The ignition switch is the "trigger" to close the solenoid.

To test, with that fan on, measure voltage on each of the large lugs of the solenoid. If more than .2 VDC drop across it, it is likely pitted and could be the problem.

Re: Strange Happenings with new Dash A/C Blower Motor

Reply #7 – August 05, 2011, 01:15:45 am

Kent, i had this problem with my 2000. It was in the condensor cooling fan in the back. It wore out and was shorting and amp draw was huge. Only happened when i turned on the ac. In fact it woukd draw so much power it shut down the ecm on the engine and it would just die. You are older and have a mechanical engine so you would not have that symptom but the tranny seems to give the same indication. Mine is the small radiator on the drivers side right behind the wheel. Took forever to figure out till Wally West called me with the idea to check the condenser cooling fan.

Re: Strange Happenings with new Dash A/C Blower Motor

Reply #8 – August 05, 2011, 10:18:03 am

John, excellent idea. I will check it at next stop. My fans are behind the front grill so easily accessible.

Re: Strange Happenings with new Dash A/C Blower Motor

Reply #9 – August 05, 2011, 10:20:13 am

Quote from: wolfe10 – August 04, 2011, 09:21:26 pm

Quote from: Kent Speers – August 04, 2011, 06:42:21 pm
OK Matt, I am now intrigued. What is a Dash Solenoid? Where is it and where do I get one if I need it?

Also called ignition solenoid (not starter solenoid). Under dash. It feeds all circuits that are hot when the ignition is on. The ignition switch is the "trigger" to close the solenoid.

I got mine from Amazon.com. Search the forums for "Cole Hershee" to find out more.

To test, with that fan on, measure voltage on each of the large lugs of the solenoid. If more than .2 VDC drop across it, it is likely pitted and could be the problem.

Re: Strange Happenings with new Dash A/C Blower Motor

Reply #10 – August 08, 2011, 11:58:17 am

Kent,

Sometimes a new problem can be traced to a recent change such as your R&R of the fan motor. Is it possible the squirrel cage is hitting or rubbing on something? You might stick an ammeter in line to check the current draw in each fan control position. Let me know and I can send a photo of the solenoid if needed.

Back from a week working on the rental house in Santa Barbara. Mid 70's with fog in the morning.

Re: Strange Happenings with new Dash A/C Blower Motor

Reply #11 – August 08, 2011, 01:19:03 pm

I found the problem. Although it started right after installing the new fan blower motor, I'm not sure its related. It appears to be the starting solenoid. The voltage coming into the solenoid was 12.76 VDC. The voltage coming out with the key on was 11.56 VDC. I then disconnected all of the red wires from the passenger side post, turned on the key and checked again, still 11.56 VDC so the voltage drop was resistance within the solenoid itself. It is possible that the new blower fan motor pulled enough extra amps that it damaged the old solenoid. The Chinese fan does create a visible voltage drop when turned on high. I order a new solenoid from Mike Graves at FOT this morning for $35. The price was low enough I thought I would avoid any errors in getting the right solenoid. I may still look for an American Made fan blower motor if one does exist.

Thanks to all for their help. I would never have figured this one out on my own.

Re: Strange Happenings with new Dash A/C Blower Motor

Reply #12 – August 08, 2011, 01:42:06 pm

Kent,

Just FYI. That is an ignition solenoid, not start solenoid.

Pretty big difference, as the ignition solenoid must be a constant duty solenoid, the start solenoid does not.

Brett

Re: Strange Happenings with new Dash A/C Blower Motor

Reply #13 – August 08, 2011, 02:02:20 pm

Good point Brett. I knew that starting solenoid was not exactly right but I couldn't think of the right name. Getting old sure is painful in so many ways.

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Strange Happenings with new Dash A/C Blower Motor

August 04, 2011, 05:13:21 pm

Re: Strange Happenings with new Dash A/C Blower Motor

Reply #1 – August 04, 2011, 05:34:19 pm

Re: Strange Happenings with new Dash A/C Blower Motor

Reply #2 – August 04, 2011, 05:53:10 pm

Re: Strange Happenings with new Dash A/C Blower Motor

Reply #3 – August 04, 2011, 06:21:38 pm

Re: Strange Happenings with new Dash A/C Blower Motor

Reply #4 – August 04, 2011, 06:42:21 pm

Re: Strange Happenings with new Dash A/C Blower Motor

Reply #5 – August 04, 2011, 09:08:53 pm

Re: Strange Happenings with new Dash A/C Blower Motor

Reply #6 – August 04, 2011, 09:21:26 pm

Re: Strange Happenings with new Dash A/C Blower Motor

Reply #7 – August 05, 2011, 01:15:45 am

Re: Strange Happenings with new Dash A/C Blower Motor

Reply #8 – August 05, 2011, 10:18:03 am

Re: Strange Happenings with new Dash A/C Blower Motor

Reply #9 – August 05, 2011, 10:20:13 am

Re: Strange Happenings with new Dash A/C Blower Motor

Reply #10 – August 08, 2011, 11:58:17 am

Re: Strange Happenings with new Dash A/C Blower Motor

Reply #11 – August 08, 2011, 01:19:03 pm

Re: Strange Happenings with new Dash A/C Blower Motor

Reply #12 – August 08, 2011, 01:42:06 pm

Re: Strange Happenings with new Dash A/C Blower Motor

Reply #13 – August 08, 2011, 02:02:20 pm

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