my car is a 93 4o th anniversary

I trying to trouble shoot a huge draw abou 4 amps

today I hooked up the battery and the blower motor ran on hi speed.

Here's the problem... I have the C68 HVAC head unit pulled there should be no way that blower comes on unless that module on the side of th blower housing is defective.

This car has and is a real PITA I've spent a month and still can't find the draw. FSM hasn't been helpful in helping me find the draw.

Anyone chime in as to why the blower motor would run with no HVAC head unit connected? Thanks

 

The head unit is just a head unit. It sounds like your HVAC Programmer is bad. It's a tiny computer located on the driver's side of the transmission tunnel, up by the accelerator pedal. You can shut this computer off by removing two fuses from the fuse box on the passenger side of the dash. The A/C Clutch fuse, and the A/C Programmer fuse. This should then cure your fan problem, but will also flash "SYS" on your dash since the CCM can no longer talk to the HVAC Programmer.

Very common issue. Chances are the capacitors in the Programmer have failed. If you're decent with a soldering iron, they're not hard to replace, and equivalent capacitors are available from Digikey and Mouser. If you aren't, BATEE.com can repair the module for you.

 

Nomake Wan would HVAC programmer cause a huge amp draw? This car was sold to me with an understanding that it has a huge parasitic draw that kills the battery. The amp draw is 4.23amps should be .003-.005 max

I've chased this for a month and a half have most of the dash, fender well and fuse blocks out running tests like the FSM says but can't locate it. I thought that little controller mounted to the outside of the blower motor housing could be the culprit. IDK I'm getting to the point where I'm now loosing my train of thought because I've tried just about everything trying to locate his short.

Batee repaired the HVAC control head I hate to think about pulling that programmer

I've been grateful for the help this forum provides

 

The computer itself cannot draw massive amounts of power--if it did, it would likely set fire to the car. However, when it malfunctions, it tends to cause a slew of systems to come on for no reason, such as activating the A/C clutch and cooling fans and possibly blower fans. As stated, the 'control head' is just a head unit--it's not what's actually controlling the HVAC system. It's just buttons. The HVAC Programmer down in the footwell is the actual 'brains' of the operation. For starters, just yank the two fuses I specified above and see how the situation changes.

If you're getting a 4.23 amp draw, you have a much, much different problem going on. If you think the blower motor resistor pack is at fault, you can always just unplug it and see if your draw changes. It shouldn't, though, and I'm betting it won't.

If it were me, I'd start by yanking the two HVAC Programmer fuses (A/C Clutch, A/C Prog). That'll at least prevent the HVAC from doing random stuff while you continue diagnosing. I highly doubt it's the cause of your draw, but it'll at least eliminate annoyances caused by the malfunctioning computer while you continue working. Then I'd start trying to narrow down which circuit contains the draw by removing other fuses one by one until the draw disappears. Then I at least know which circuit is at fault, so I can look at all the devices on that circuit in the FSM and narrow down the actual cause.

 

I've done exactly that and not one fuse changes anything on the meter.

The maxi fuses that are located on the firewall I am looking at because when i moved the 60 amp power accessory fuse back and forth I noticed the draw hanging to zero. I question that because the ecm should draw something??

 

I'm not sure I follow. Are you only looking at the maxi fuses? There are three fuse blocks in our cars; two fuse blocks in the engine bay that use maxi fuses, and the fuse block inside the car that uses mini fuses. If I am reading you correctly, however, then at the very least you have rounded down the culprit to every single circuit connected to the Power Accessory maxifuse. Time to crack open your FSM and get tracing.

 

Have you tried disconnecting your alternator? Sometimes the diodes can go bad and allow current to flow backwards to ground. I'm talking about the red power wire.

 

I've had this problem and for me it turned out to be the blower control module mounted on the blower box. If it goes bad (and they do!) it can either keep you from getting any blower control OR it can run your blower with the key on / head unit off....just as it happening to you.

 

And as luck would have it, I just remembered that there is a member here selling a pair of them (one new module one a good used unit) for C68 1993-96 cars here ----> FS: Blower control module

 

thank u

 

yes checked that. Did find with everything disconnected a 12 volt trouble light lights up when u touch alternator case or the intake on the motor. Appears like power wire is grounding somewhere. It's intermittent which is bad.

Had car on rack looking at wiring under car, wiring that routes over back of transmission and wiring to various relays, solenoids etc.

all fuses at I/P are good none when pulled affected the draw

maxi fuses in engine compartment all checked okay but I did find one thing odd

when I moved the 60 amp power accy fuse with my thumbs back and forth I noticed meeting changing drastically from 4.25 amps to zero amps so I disassembled the fuse box to see where the wires come in and honestly didn't see anything burnt, crossed or abnormal that could cause an amp draw.

I did see additional grounds when I put the car in the air making me think PO was chasing some of the same things I am looking at.

CCM sent out and verified ok
Batee repaired hVAC head
pulled antenna relay no change
disconnected alternator no change

I thought this was going to be easy. Pull a fuse if it makes a change in the meter locate the circuit in the FSM but that hasn't happened

 

I sent him a PM thanks for the help

 

pulled all I/P fuses one at a time no change but I will pull those to aid in troubleshooting. Thanks

 

I have pulled and checked the fuses in the I/P and both engine compartment fuses nothing bad

 

Except of course the 60A Power Accessory fuse which you've just stated causes the draw to vanish.

 

I am pursuing that circuit. Because this is intermittent its been a royal PITA

I am going to remove he wires from the block, clean and inspect see what happens. Thanks for your help. Wardie

 

Had a chance to get back on the car today following the 60 amp accy circuit. I pulled the power seat circuit breaker and the draw went from 4.23 amps to .001 amps yahoo thought I got it.

Pulled the plug apart on drivers seat and on passenger seat put circuit breaker back in now amp draw reads 7.22 amps? Oh my how could that be? power seats disconnected yet I'm almost double amp draw from original 4.23 draw which BTW the draw should only be around .004-.005 max amps.

I'm crushed. Could really use some help here guys.

 

Don't be crushed, just think about it logically.

You unplugged the seats, but the draw remains. This means the problem wasn't in the seats themselves, but could be in the wiring on the car side. If there's a chafed wire that's shorting battery to ground, that would most certainly do it. Please inspect the vehicle side of all the power seat harnesses thoroughly, including running continuity checks. It may be worth it to unplug the battery for those checks just to be safe.

 

will do just didn't understand why the draw increased with seats unplugged unlees we pulled the harness when disconnecting the plug?

 

The seat's internals may have affected the circuit's behavior. Let's worry less about that for now and instead focus on what's in front of our eyes, which is that you've whittled it down to the power seat circuit, and by disconnecting the seats, have whittled it down to the vehicle side of the wiring that goes to those seats. That's great detective work! The end is near!