My 90 has the digital controls. The unit seems to work fine, but my blower motor will not turn on every time. To add insult to injury the motor will kick on when I hit a bump. Now it will only turn on and blow softly and not kick in and blow hard. Yeah I know how that sounds!

Suggestions on what to chase here? Blower motor, switch, plug, etc? What normally goes wrong on these?

Thanks!

I should also note that I have a possessed door sensor switch that sets the alarm off at random times and the interior lights go on and off whenever the evil spirit inside tells it to do so. Don't think that this is connected but should be mentioned just in case!

 

That's a $64,000 question trying to figure out the A/C. I have a lot of similarities as yours and can't turn the fan speed above 5 or it stops blowing. After 3 months tinkering around with it, I've giving up and taking it to the shop in the morning to get an answer.

 

Let us know the results!

Anyone else have an idea?

 

The control head needs to be removed and the circuit board examined under magnification and defective solder joints resoldered. This is a common problem with aging C4's.

 

When you say control head.....are you talking about the digital control box and the pieces inside?

Sorry to sound stupid here, but well, I guess that I am!

Thanks for responding! That will save me lots of money in chasing parts!

 

The control head is the unit in the dash that you select heat, a/c, blower speed etc. That unit needs to be removed from the dash and taken apart and the circuit board looked at for poor, cracked solder joints and then replaced back into the car.

 

Thank you very much. I thought that was what was being referred to, but I wanted to make sure before I jumped in and made another problem!

 

Could be - but the '90 uses the Programmer as the Processor, not the Control Panel like the earlier Years. Whatever is selected at the Controls is sent over a serial data link (meaning that checking voltages isn't going to tell you anything) to the Programmer. The Programmer, using signals from the Inside and Outside Temp Sensors (except at Auto 60 or 90 when it defaults to max), then controls Blower Speed by sending low voltage signals to the Blower Module (on the Evaporator Case), and controls the position of the temp door, based on the temp setting selected The blowers signals (which you can check) are about 2.5 volts for the lowest, 6 volts or more for max. The Module amplifies those signals and sends 4 volts to the Blower for low, 12 for high. Easiest to troubleshoot with a bidirectional scanner as the Programmer is linked to the CCM and you can use that link to see if will work. If it does, the control panel is bad or the serial data lines are funky. If not, the Good Book says to replace the Programmer. I'd do a couple of other checks first:

1. Blower signal from the Programmer is the Brown Wire. Check it's voltages at "1" and "10". Should be 2.5 volts - then 6. Output is purple. Should be 4 volts - then 12. If it has the inputs, but no boost, replace the Module (available at NAPA and it's the same part for all GM's with electronic controls so don't let anyone hijack you on the price).

2. Check the Blower connector for discoloration. As the motor ages, it ramps up the draw and these connectors are usually crimped, not soldered which can really heat the wires up (mine melted under warranty - oops!). If the Purple is no longer Purple, take the weatherpak apart and solder the connectors to stop the voltage drop.

3. The Programmer also controls the compressor "on" signal to the PCM. An intermittent at the Low Pressure switch can wreck havoc on the whole system. Wriggle the connector around and see what happens - on the '90, I think it's still on the Evaporator outlet (bigger line at the top).

If the above checks out - I'd place my money on the Programmer, but you might have it checked out by a shop that has a scanner. Pep Boys offers their $29 a/c checkup special but I don't know if they have the right tool. GM flatrate is something like .5 for a quickie, so at normal shop rates, shouldn't cost you more than 50 Bucks (I'd sit and watch them do it and then make up my own mind about what it needs).

 

On my 90, I took the control head apart and cleaned the board where the buttons contact it. Not hard to take it apart.

I actuallly had to scrape it with a screwdriver. Started with alcohol on a q tip then an erasure, looks to me they did not keep all the insulation off the contact points when making the board, at least on mine.