Next Project: A/C system doesn't work

Assuming that it isn't that the terminal in the horizontal k white connector with the two brown wires is burned up (the usual cause of this problem) -- measure the voltage between the terminal in the k connector with the two brown wires with the key "on" and the negative battery terminal (with the k connector plugged in). Should be +12V:

If not +12V = upstream problem on the fuse-relay panel (e.g., bad AC relay, broken trace, bad fuse, etc.)

If it is +12V (but the blower doesn't work at any speed) = don't want to go there...

Yes.

 

This should be a much easier fix! Don’t know how u could stay with no AC in Florida but I know here on so cal u going to need it!
Looking forward to ur next adventures!


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What turns on the ac anyway?

 

I only had the A/C working on my car once. I don't remember how to turn it on.

 

No wonder most of the "chicks" Shamile showed in his car weren't hardly wearing any clothes! Who would have thought he was THIS devious?

 

I had the same issue and it was the thermal switch next to the blower on one of the lines (its covered with that sticky black stuff to insulate it so look close). There is a vent that is easy to remove (four bolts) in front of the left front tire, You can buy pass the thermal switch with a jumper and see if that is it as fan will run nonstop anytime you tun on the AC. But since you don't get any air with vent on, you can put 12 volts on the fan at the fan to see if it works. Its a wet dirty area were the fan is and it could be a corroded or dirty connection at the fan.

 

The fan in the drivers side front of the wheel is for the condenser. This is not related to the interior blower fan not working.

 

Right, good point, oops.

 

Has the fuse panel been replaced? Can you provide pictures of the connectors described by Mr. Magnusson? This is where I would start, then work your way back. The fan is incorporated into the evaporator unit (which is behind the dash), but that doesn't mean that's the problem. There is a fuse in some speed control switch mechanisms as well, not in my earlier type but I recall reading that it exists in others.

Electrical problems are not hard to diagnose at all and while they may require some head scratching, they don't require any of the effort that you've already been through! The trick will be to really diagnose exactly what's wrong rather than give up and take the approach of replacing this and that until you've solved the problem, because that will get expensive. And frustrating.

 

I have a pretty dismantled Testarossa right now. I just noticed a fuse in the housing for the speed control in the center console. I Didn't remove it, but I could. This may be the fuse xplodee is referring to. The first thing Jamie should do is determine that his blower motor works. I haven't searched the forum for which relay controls this .A jumper wire between a couple of pins and the blower should work. I'll look at my schematic and determine which one of the four relays mounted on the passenger side of the underdash relay cluster controls the blower motor. Awkward to get at, hopefully Jamie isn't 200 pounds. there's a combination of vacuum operated valves and electrically operated doors that are used for air control. With ALL of my interior pretty exposed at this point, it wouldn't take long to figure out the system. I'd bet the small fuse in the speed control, just protects the electronic side of the climate control system, possibly including the small door motors that move the flaps on the side of the blower assembly..

I'm dating myself, but I was working on these cars in the early nineties, and was doing what I called a fuse box bypass. IT was immediately apparent these cars had issues with too many blowers and motors going through the fuse box. It's been twenty five years since I was doing these. Not just a Ferrari problem, but a LOT of cars made in the eighties had similar issues with the high current draw circuits causing problems. Mercedes, BMW's, Honda cars all had issues. Back then- no internet- just had to figure it out with schematics. My Testarossa schematic book has a lot of my writing in it!

 

Going from Steve's post on voltage from the K terminal with the brown wire, it goes to a relay mounted on the bottom of the blower unit. The key on power is applied to the relay and continues to the blower motor. The blower motor has 12 volts applied to it whenever the key is on. The power transistor OR the relay provides the ground for the motor. If the blower motor is bad, there is a way to check it without ripping TOO much apart.

If you can get your car up in the air, and still open the passenger door, you should get the car to a semi comfortable height, as you have to work in the passenger footwell to diagnose the problem. The car raised up a couple of feet should make this semi painless.You will have to remove the front carpet, and with four screws remove the footplate. The power transistor is fortunately wired into the circuit with it's own three wire harness and plug. The power transistor is IN the AC/ Heater box and is accessible by removing the center vent. You DON'T however have to get to it. The transistor is well to the right side of the cavity, Almost directly behind the left side of your glove box, even with the center vent is a cable coming through a hole. A black plastic shielded cable, about the size of your pinkie finger.This cable runs down to the left side of the foot well, where hopefully you will find the WHITE three wire connector. It comes out without any drama, and you now have a pathway to see if your blower motor is good. The wire that attaches to the COLLECTOR of the transistor is used to provide an alternate ground for the blower motor. This wire will show 12 volts if your fan motor isn't broken. BUT grounding this wire should cause your blower to run. I'll get the wire color tomorrow, because frankly I didn't write it down. The simplest way however would be to jumper the relay, but that relay REALLY is hard to get to. In the group of four relays, it's the far left relay. I can get my relay in and out without too much grief, but it IS tight.

I haven't found the twelve wire terminal that applies power to the blower assembly. It appears to exit the blower towards the firewall. This would be the ideal location to troubleshoot from.I always like to divide my circuits in half, instead of starting from one end. Saves a lot of time, IF you can effectively reach the center of a circuit.. IF you find your blower works, then it's simply a matter of figuring out where you've lost power. There is a series of plugs in your passenger footwell, that attach all of the center console wiring to the rest of the car. On my car I have about five GREEN connections. Green as in corrosion has built up. These probably will not pass any current. They unplug pretty easily. Unplug them and take a look for any corrosion. Just the act of disconnecting and connecting the plugs, can wipe them clean enough, if they're not very bad.

I'm using an 86 TR as my sample. It does not have a good battery in it, and I think I'll stick one in, so I can check out MY blower too. I'm hoping your 91 is the same. I have a 1990 that's completely together and functioning, but it's stored too tight to my other cars to get in the passenger side.