heater diagnosis

[jerseyben]

I am trying to diagnose why the blower motor won't come on in my 1980 CJ5 .
The PO told me everything was replaced and that it was working fine when he had it.

Turn the key to on, turn the blower knob on any setting and nothing. The volts are noticeably dropping but nothing is blowing. A test light is showing that juice is getting to the back of the blower motor. I cannot hear any noise coming from the heater box area at all.

Here is the weird part: I actually picked up a new blower motor and I decided to test it. But when I hooked up the wire to the back connector and turned the blower knob to any setting the new motor wouldnt turn on either.

Am I doing something wrong here? What else should I check to diagnose this (simple) problem?

 

[54cj3b]

is the fuse good are you getting power, bad ground, busted wire somewhere, bad switch
few things to check

 

[KenB]

Suggestions: First, check the ground connection.
On the old, installed motor: If you're getting a voltage drop when you turn it on, but no rotation, it could be locked. This could be worn bushing (bearing), lack of lube, or debris in the fan. Or a faulty switch.
On the new motor: Try a direct, temporary hook-up i.e. positive to + battery terminal, ground to - battery terminal. If it runs, then the problem could be in the switch.
You could check the installed motor the same way with jumper wires.

 

[Cheepjeep85]

if you are getting power to the blower motor and you have a new motor, i'd say you most likely have a ground problem.

 

[jerseyben]

There is only 1 connector for the motor and only 1 wire running to it... Where is it grounded?

 

[KenB]

Case ground. The body of the motor, through the mounting bolts, supplies the ground connection.
That's one of the quirky things about auto electric circuits. The ground (negative side of the circuit) isn't always a wired connection, but it's gotta be there.
In some applications, such as the blower motor, the ground connection may have several points at which the circuit might be interrupted (motor mount to blower housing, blower housing to firewall, firewall to frame, etc.) An easy way to check is to scrape a bare spot on the problem device, then use a jumper wire with alligator clips to a known, good ground. Well, maybe not always easy, cause some of those components can be hard to get to.

 

[IOPort51]

sounds like your pulling amps, I would check the blower wheel and see if it is jammed in the volute. and if you set the case of the new motor on the negative terminal and jump the positive to the terminal on the motor it may very well run.

I think I would check the fuse size, if you are hung up I would think it should overload the fuse before the motor burst into flames.

 

[SrBeaver]

if you have voltage at the connector on the motor, check ground first. If ground is good you can take a small hammer and lightly tap the motor housing when the switch is in the on position. If motor turns then replace blower and clean ground area before you install new blower. I also like to add an actual ground wire to then to help alleviate issues being mine is under water quite a bit and gets corrosion build up easily.

 

[priceg]

Fan speed resistor?

 

[jerseyben]

I will hot wire the new and old motors and see if I can get either one to spin that way. I will also check the fan on the old motor to see if it will spin freely by hand.

Thanks for all the suggestions!

 

[jerseyben]

Replaced the blower motor with a Blazer motor as specified in several "upgrade write-ups". Re-installed, etc.

The fan spins freely but NO AIR is coming out of any vents.

I ran the engine for 15 minutes. No heat, no hot air, no moving air. Nothing. I tried moving every lever on the box. No difference. The coolant lines going to the box were hot to the touch but the box was not hot or even warm to the touch anywhere.

I give up...

 

[CJKrawler]

Don't let it defeat you. Did you make sure the heater core was moving fluid freely? Do you hear the fan running?

 

[jerseyben]

Both lines to/from the core were hot to the touch. The fan cage is moving and spinning freely on all 3 speeds.

There is literally no air coming out of any opening in the box. I am perplexed...

 

[IOPort51]

is the fan motor on the inside or outside of the fire wall?? if, as I suspect, the motor in in the cab then the blazer motor may be turning the wrong way. also check the ducts to be sure they are not blocked and the dampers are open.

 

[1970 beepbeep]

Does it have/ or need a blower resistor?

 

[jerseyben]

The blower motor is sticking through the firewall. It actually sits in the engine bay with the fan part inside the cab.

Now that I think about it, there is a good possibility that the blower motor is turning the wrong direction. How would I reverse the direction the blower motor turns?

 

[jerseyben]

Update:

The PO had the fan (squirrel cage) turned around facing the wrong direction. So not only was the old blower motor seized but the fan was on backwards.

Additionally... After replacing the blower motor with a better Blazer blower motor and putting the fan (squirrel cage) on facing the correct direction with the open end facing me, I had circulating air. The vents blow air strongly on all speeds now (and even better after sealing the heater box with Permatex #2 and a thorough cleaning). BUT, still no heat - only blowing cool air which eventually turned slightly warm after 15 minutes of the motor running.

The culprit was the PO had removed the Thermostat completely (I dont know why). I went to Advance Auto and picked up some RTV, a 195* Thermostat, a Gasket, and Coolant. A half hour later I was up and running with working heat. I also learned that my temperature gauge does actually work.

 

[dslywalker]

Update:

The PO had the fan (squirrel cage) turned around facing the wrong direction. So not only was the old blower motor seized but the fan was on backwards.

Additionally... After replacing the blower motor with a better Blazer blower motor and putting the fan (squirrel cage) on facing the correct direction with the open end facing me, I had circulating air. The vents blow air strongly on all speeds now (and even better after sealing the heater box with Permatex #2 and a thorough cleaning). BUT, still no heat - only blowing cool air which eventually turned slightly warm after 15 minutes of the motor running.

The culprit was the PO had removed the Thermostat completely (I dont know why). I went to Advance Auto and picked up some RTV, a 195* Thermostat, a Gasket, and Coolant. A half hour later I was up and running with working heat. I also learned that my temperature gauge does actually work.

Cool you can say now you won the battle.Hope there is no more PO episodes