I'm having a problem with my blower not working. My car is a 1990 convertible na. The blower has not worked since I purchased the car.

At this time, I am not too concerned with the AC or heat, but eventually would like to get it all fixed. I am only looking to get the blower fan to work now.

The logicon lights up, as do the indicator lights for the different selections I make (such as floor/vent/mix/defrost and re-circulate). The AC indicator light does not come on (at this time there is not a belt on the compressor). The fan speed slider does not work (the fan does not turn on).

When I select re-circulate/fresh air I see the damper open and close (when I have the blower motor removed).

When I select the different 'air zones' (vent/floor/etc) I can see the damper move behind the vents.

I checked the fuses, and they are all ok.

I removed the blower motor and connected it to a 12v power supply and it came on- fast and strong.

I removed the logicon and re-soldered the connections.

I removed the relays by the blower motor and checked them with a 12v power supply and a meter and they are all working.

I have not kicked it yet.

Does anyone know how to test the logicon to see of it is working ok? I'd hate to buy another to find that is not the problem- or am I going in the wrong direction?

Thanks,

Matt

 

You are going in the right direction.

There is a procedure in the FSM to check the blower motor outputs of the logicon. One is a variable voltage that goes to the power transistor; another is an on/off signal that triggers the relay that bypasses the power transistor.

If you are getting good voltages at the back of the logicon, look for the same voltages at the corresponding pins of the blower motor harness connector (right rear of the motor housing).

If the signals are making it to the harness, but not getting to the motor, it is likely in the blower motor harness, the power transistor, blower motor resistor, or their connections.

See pp. U-11 thru U-14 of the FSM. It gives the pinouts to check at each of the locations, including the logicon. Its in Ch 16 of the FSM, which you can find at...
http://www.teamfc3s.org/main/factory...AC_systems.pdf

 

Calpatriot, thanks for the reply.

I got the FSM and went through the troubleshooting and it indicates that the fan amp is bad. I picked up another fan amp (the entire logicon w/amp) from someone this weekend, and I am getting the same result with it. I tried my logicon with the new amp and vice versa with the same result.

One thing I am thinking about is the wire/plug on the back of the logicon. Not the 2 plugs on the back, but the wire harness that goes into the dash. The plug itself is very easy to get to. Other posts I have read indicate the plug is not easily accessible, and you need to work to get to it. However, the plug on mine sticks out so far that I have a hard time folding it back into the dash to replace the logicon. I can remove the upper dash to check it, but I'm hoping to avoid that, wondering if there is a simpler way to test the wire harness from the plug itself- by checking for voltage or with an ohm meter?

Also, I really don't want to buy another logicon if the two I have are good. Does anyone know if I could send them to someone to test them? Of course, I'd pay shipping...

Thanks,
Matt

 

What test did the logicon fail?

you can test the harness with an ohm meter. If you have access to the plug the logicon hooks into, then separate the connector at the blower assembly, and identify the same pin there. Check the circuit for resistance (it should be zero) and resistance to ground (that should be infinity).

You can also hook up the logicon and separate and or backprobe the connector at the blower assembly and see that the appropriate voltages are present at the connector. That would verify both the logicon and the harness.

On pg U-29 of the online FSM there is a diagram and voltage chart for checking the outputs from the fan amp. If you can verify the presence of each of those voltages at teh output of the fan amp, it is ok. Then you need to find those same circuits at the connector at the right rear of the blower assy and verify those same voltages are there.

 

All tests were good till I got to 29- the test results I got were:

Switch on: f=12v and h=12v (should be less than 2)
Switch off: f=12v and h=12v (should be 12)
Blower low to max a=0 (should be about 5 - 12)
Blower on max i=0 (should be less than 2)
Blower on medium i=0 (should be less than 12)

 

I have not had any more luck with this since my last post- I am wanting to know if anyone knows where I might be able to send these two logicons to have them tested? That would at least tell me I have a problem with them or something else...

 

The FSM contains a truth table you can use to verify correct operation of every output on the logicon.

If you pull out the glovebox, you can gain access to the blower assembly and its connectors. You can verify voltage at the connectors: if it is there, the logicon and harness are ok; if not, the problem is in the blower box.

You can also drop the blower out the bottom fairly easily (three nuts, one electrical connector) and test the blower on the bench. There is a spec for its resistance, and if it passes that you can put voltage on it and see it run.

The blower runs on power through a transistor on the front side of the housing, current through which is controlled by the voltage from the logicon slider through the fan amp. At full scale, the system bypasses the power transistor, and the hi blower relay kicks in and puts 12v directly across the blower pins.

Using the specs in the FSM, you should be able to verify each of the required voltages are present at the pins on the blower connector. If one is not there, the problem is upstream (logicon, fan amp, etc)

 

The transistor is blown.

The little (a) gives you that indication. There is no voltge on your car on little (a) a'tall indicating the transistor is kaputski. On my series four cars that transistor is located on the top fwd side of the blower HOUSING.

Not related to the above...........if you push the lever to the right and push the A/C button and the compressor clutch does not go CLACK...........then your mabe low on refrigerant. Theres a low pressure switch involved and it the pressure in the system is too low the switch will not provide a circuit to the compressor/a/c relay/whatever.

So jumper this low pressure switch. Its located on the dryer in front of the radiator. Pull the two wires off and jumper them with a piece of bare wire. Then a/c to ON and key to ON and slider to at least half way or more to the right. Compressor clutch goes CLACK.

There's a bit of jumpering you can do to see that the blower does in fact work. You pull a relay out and jumper two sockets in the elect plug. I'll remember the relay and color of wires later in the day.......maybe.

Personally I'd have used the pages U-12 and done them first, from top to bottom and make sure all three fuses are good before doing so. They are listed on U-12. I believe all the elect plugs MUST be attached when doing this. Use a sewing needle to ***** the wire insulation (damned to eternal damnation if you do this on a airyplane).

As you can readily see in the attachement, if you FIND the EX-HI relay and pull the plug off it........and then jumper the Blue/White to the Yellow/Red in the elect plug..........the motor will go whizzzzzzzz spin.............IF the key is ON and IF the HEATER 30 amp breaker WAAAAY up at the top of the interior fuse panel.................is any good. You make sure that breaker is good by key to ON and with a meter checking Red/Yellow for batt pwr.

This little workaround is also dependent on the HEATER RELAY being pulled in when the slider is put to the right at least a quarter inch or MORE. Key to ON and slider to the right should get you a CLICK sound from the HEATER RELAY.

You can ID the EX-HI relay by the colors in the elect plug. LIke L/W and R/Y and L/O and such. The other relay does not have those color wires.

The LG/B wire on BOTH those relays should show batt voltage with key ON. No slider action required for that . No batt volage???? then the fuse for WIPERS is kaput. Then again, maybe not the wiper fuse but the METER fuse and is suggested on that page U-11.

Lots of different ways to work this little deal, not all by the manual. We worky airyplane problems not using the FI's ......but shhhhh, don't tell anybody. Big trouble if caught varying from the FI....sometimes. FI sucky sometimes. No since being stupid and following sucky instructions.

By the way, I'm and EXPERT! Two out of my three cars have the blower mtr working.

But then once again, neither of those relays will pull in even if they have power.......................IF the gnd for those two relays is not coming from the LOGICON on the L/O or G/R wires. If you hear the HEATER RELAY pull in when you move the slider to the right.......then you KNOW the G/R wire from the logicon is good. So no need to verify that any further.

 

Thanks for your quick replies...

I'm not trying to get my AC to work at this point- just my blower. I'm sure the compressor is locked up- there's not even a belt connected to it. However, I will test to see if I can get the compressor to click later tonight, just to see if it is getting a signal from the logicon.

I did go through the steps in the FSM, and got to page 29 (Checking Fan Amp) before I found a problem.

Turn Blower Switch On: f and h should be less than 2, I got 12.
Turn Blower Switch Off: f and h should be 12, I got 12.
Turn Blower Switch From Low to Max: a should be about 5 - 12, I got 0
Turn Blower Switch to Max: i should be less than 2v, I got 0
Turn Blower Switch to Low: i should be 12v, I got 0

I took the blower out and tested it and all relays. I recall the FSM went through the steps of testing the transistor and it all tested ok. I'm stuck on the fan amp.

As I mentioned before, I don't know if it's the fan amp, or the cable that the fan amp connects to. The cable in my car is easy to pull out and disconnect, as opposed to others who have said they have to disassemble their dash to get to the plug.

 

Jumper the wires I mentioned and the blower will work. The L/W and R/Y wires in the EXHI relays elect plug.

Does the HEATER RELAY work of not. Goes CLICK or not when the slider is move to the right with key ON and ALL elect plugs connected and ALL fuses good?

Does the R/Y wire in the EXHI relays elect plug have batt voltage on it or not with key ON?

 

Strange- your earlier post stopped with all that I quoted- Lots of other useful info in the remaining post. I will try this and see what happens. Thanks again!

 

Earlier I meant the relays get gnd from the Logicon on the L/Y and G/R wires NOT the L/O.