87 300 td - blower motor, regulator, or control panel
 

I am trying to diagnose a blower fan not working. I have taken everything out to get to the blower motor and I think got some confusing diagnostics in checking voltages.

I checked the three pin connector at the firewall and had only 5v on red and anywhere from 1.5v to 5v on yellow. I read on another post I should have 12v on red. I checked and double checked this one.

I checked the voltages at the motor leads and they were way low - less than an amp.

I am not sure if this indicates the control panel is bad, or if the regulator is bad?

I had previously taken the blower motor out, and verified it was running by connecting it directly to the battery. I also oiled the bearings because it squeaked some. I also replaced the flat metal 30a fuse and box on the driver side hub because it had melted through the bottom and the plate fuse was cracked nearly through.

The motor squeaked when it last ran - so it likely had a lot of resistance - and could have fried the controls or the regulator. Like I mentioned I have since oiled it and verified that it runs - an am hoping I don't have to purchase mulitple items to get my ac blower going again.

most cars have a resistor box for adjusting the speeds of the motors, since you obviously have drawn excessive current through the wiring, I'd find that box and remove and clean the connections, and reconnect, then start looking for burned wires.

You should have 12v/battery voltage at the 3-pin connector, chase that first.

Okay - I found the wiring diagram with the additional blower motor fuse (which I have) and it looks as though the the 12v feed at the 3 pin connector (power/ground/climate control panel) comes from the ignition to the blower fuse and back to the 3 pin connector/harness for the regulator - so my drop to 5v is somewhere along that length. I figure the harness must be bad from when the fuse melted the first time.

Now the motor had started to squeak and must have had excessive current draw that fried through this circuit - so what I don't know is if it messed up the regulator or possibly sent current back from the regulator to mess up the climate control panel.

I am considering ordering a replacement wiring harness, regulator, and new motor, and to start by replacing the harness and then take some current measurements at the motor - but most likely the motor although it spins and I oiled the bearings will cause this problem again because it is a 23 year old motor. I want to have the regulator on hand just in case it is fried too. I will hold off on worrying about the climate control panel.

I can send the parts back I don't end up needing.

Start at the beginning of the current path, ignition switch, fuse (both sides), etc. You will find where the voltage drops (measured to ground) and therefore the weak link.

Where can you measure the voltage on the ignition switch and how do you get to it?

I got it figured out - regulator - and replaced.

I was able to get voltages measured correctly - had to go to the battery negative - but it worked - and then I jumped the blue wire to battery negative to confirm that the mootr was fine, but regulator wsan't. I got it replaced yesterday - and now on to a new issue I will post seperately: tach and compressor connections - as even though I got the blower working - my AC compresor is not coming on.

Thanks for all the help!

check your kilma connections.

yep - checked both the ovp relay and the klima - the fuse seemed okay on the ovp, and didn't notice anything unusual (melting, burnt etc.) on either. I ordered both for replacement and will see if I can get by with first the ovp and then the kilima if needed. I hunted around to see if there was any good test but didn't find much that helped. I tried bridging the 5 to 7 pin on the klima and that didn't work to start the compressor which makes me suspect it is the ovp - or worse my compressor is bad. parts should be in by wednesday - and boy do we need the a/c!

The Klima relay has several inputs, all of which must vote "YES" for the compressor's clutch to engage. A simple test is (with the engine NOT running) to disconnect the connector at the clutch and momentarily connect the clutch directly to +12V and ground (polarity doesn't matter). You should hear a "clack" noise as the clutch engages. No noise, bad clutch. Separably replaceable, I believe (ask Sixto for details).

The compressor has an RPM sensor that can tell if the compressor has frozen due to (for example) a bad bearing. If so, Klima turns off the clutch. This protects the serpentine belt.

Klima looks at engine RPM via the tachometer line. The purpose is to keep the compressor load off of the engine when the engine is first started. Engine RPM must be up to at least 600 or Klima won't allow the clutch to engage. No tach function, no a/c.

Klima looks at a full-throttle switch located in the linkage near the cruise control actuator. (This is NOT the kickdown switch under the pedal.) When you floor the accelerator, Klima assumes you need maximum power and turns off the compressor. If this switch or its wiring have failed, you get no a/c.

The a/c refrigerant line has a dual-pressure switch near the dryer (driver side, front of engine compartment). Too little pressure or too much shuts off the compressor.

Jeremy


The CCU must "tell" Klima to turn on the a/c compressor. CCU looks at various temperature sensors and the thermostat dial to make this decision. An electronic failure could result in this "request" not getting to Klima.

Tested Clutch
 

Well - I am looking for input. I could not get to the power input to the compressor clutch, and there are multiple connections down there. I assume one is the speed sensor and the other the clutch. The wiring harness that serves part of it does not appear to match up perfectly with the colors I should be seeing, and part of the power is coming from a harness I can't get to as the wiring must come through the engine.

So I couldn't get to it to bring power directly to the clutch. I did remove the Klima and jumped the 5 (power) to 7 (clutch) and I did get a click - not really a clack - and I felt on the compressor and there is a vibration when that occurs - but it sounds more like a solenoid. It is difficult to determine because checking it that way there is a lot of clicking from vacuum check valves and such.

Okay - but here's the question - with the klima in - I do not get that click or vibration at the compressor - so it might signal that there is something else that is keeping it from engaging - but it also wasn't like the engine was on - so the lack of rpm should have kept anything from happening.

Any thoughts on this - or is there any way to test the dual pressure switch or the full-throttle switch?

Jimmy

Sounds like when jumping klima you managed to get the magnetic coil that draws the clutch in to function likely if the engine was running the compressor plate(shaft) would have been now turning. You could at least verify function with engine running and blower running, diagnosing the sound or condition of the compressor and possible cooling before spending alot on the electrical components when expensive refrigerant components may need replaced also or first.

Unfortunately The functions of the safetys of the compressor electrically on theses cars through HIGH/LOW switch, Coolant Temp switch, CCU, Klima and Speed Sensor to name a few (possibly also evap coil low temp safety) is a foreign languauge to me and I could even try to explain it to you. Id assume someone who has troubleshot that portion before will chime in.

Good luck

Arlo