It seems my fan only comes on when I have the defrost on. Not the A/C, the defrost. Wtf got wired wrong now?

There is a wire from the AC controls to the fan relay. That doesn't run though the ECM. The ECM could OR the AC controls could turn on the fan. Sounds like the problem is in the AC controls.

We are talking about the radiator fan correct?

[This message has been edited by phonedawgz (edited 02-07-2011).]

yes, the radiator fan... The fan doesn't ever seem to come on otherwise... /fail

[This message has been edited by lou_dias (edited 02-07-2011).]

In a 4.9 the fan is controlled by the PCM. Double check the wiring. If you have a scanner put it on a verify the PCM is getting a temp signal. The AC should overide and power the fan directly but I've seen swaps where it didn't. Point is it should come on without using the AC, or in your case Defrost.

from the CTS I'd imagine...?

The fan request from the computer ties into the HVAC request at the C100, and both control the same circuit for the fan relay. Either the computer will command the relay, or the HVAC, or both (one doesn't cancel the other, they both ground the fan relay). I have the wiring diagram in front of me. The HVAC panel has contacts to ground the relay at "MAX", "NORM", and "B/L". I understand that many other cars also turn on the A/C when selecting defrost (and subsequently the fan when the pressure switch trips) to dry the air on the windshield, but the Fiero diagrams show no provision. Defrost has absolutely no control over the fan, there's no way it can ground the relay feed unless there's a severe short on the HVAC circuit board or the wiring which plugs into it. Each of these seem highly unlikely. You're sure it's the defrost setting on your HVAC panel that's turning on the fan?

[This message has been edited by L67 (edited 02-08-2011).]

If the 4.9 was installed at the Fiero Factory they add a wire so the defrost button will turn on the fan.

Jack

Out of curiosity, what is the point of having the fan run while the defrost is on?

The A/C runs with the defroster on. That is what my diagram of the heater controls says.

[This message has been edited by phonedawgz (edited 02-08-2011).]

quote Originally posted by phonedawgz: The A/C runs with the defroster on.

Ahh ok, I see that now in the compressor diagram. The HVAC has no provision for controlling the fan with the defroster button. The A/C pressure switch would still trip the fan when needed, but I suppose having the fan come on permanently during defrost could increase peace of mind.

quote Originally posted by J Gunsett: If the 4.9 was installed at the Fiero Factory they add a wire so the defrost button will turn on the fan. Jack

Considering the quality of the swap I've discovered so far, they probably killed the A/C and only defrost works right now.
Regardless, my CTS is not triggering the fan to come on.

87s and 88s have that fitting plugged and/or capped off, since the heater hose return is "teed" into the coolant pipe.
I've seen the rubber caps deteriorate and blow off, usually at the most inopportune time.
When I replaced my water pump, I filled that tube with JB weld and then put a cap and clamp over it. It ain't going to leak.

The ECM is supposed to turn on the fan. The ones I've seen are programmed to kick on at 212 degrees.

If you look at the top of the AC control head, and the connector, you can see the wire that turns on the fan. In many cases, there's a circuit trace that will burn through, and stop the fan from coming on with the AC. I've fixed one, but it's been a while.

[This message has been edited by Raydar (edited 02-09-2011).]

quote Originally posted by lou_dias: from the CTS I'd imagine...?

Well, yes and no. The CTS feeds the PCM, but the PCM is what actually activates the fan. It depends on what the fan on/off temps are set at in the PCM (its adjustable in the programming). Stock programming or custom chip?

Custom. Should be at either 185 or 195. If that circuit goes to the A/C controls then that could be why it's not coming on. The defrost does turn on the fan but not the A/C.

So the stock wiring for the radiator fan relay control is that the wire runs to BOTH the AC control panel and the Cooling Fan Temperature Switch (mounted on the engine). Usually that wire is extended to the PCM. That allows the PCM to control the cooling fan instead.

So the problem with the fan only coming on in Defrost is most likely a problem in the AC control panel as stated before.

Since you also say the PCM doesn't turn on the fan, that would be a separate problem. I'm not sure if your PCM custom program is supposed to be programmed to turn on the radiator fan with the AC or not. Either way since the defroster turns on the fan but the AC doesn't the problem has to be at the panel. Does the AC compressor run in both AC mode and DEF mode? If so the problem again would be the fan wiring at the panel. If however the AC compressor only runs on DEF, perhaps the PCM is turning on the fan, but the AC control panel has a break in the compressor control circuit.

So if the compressor works on both DEF and AC, then you know the problem isn't that the panel has a problem in the AC request line, but instead it would have to be in the direct wire to the panel that runs the cooling fan.

And if the PCM isn't turning on the fan at the required temp you would also want to check to see if the rad fan request wire is working. That wire is (or at least was) on D1 of C500. That wire would be a dark green with a white stripe. Most likely that wire was extended from C500 through the harness and to the PCM. You could with the key on, ground the wire and see if the fan turns on. It should.