Originally Posted By: SteveSRT8
yes, modern vehicles run the fans for a variety of reasons.
I was quite surprised that the same parameters trigger the PT fans as trigger my LX. On mine, the fans run at low all the time if climate control is on. I get a high speed burst when first started after a heat soak. Then I can get high speed for trans temp, AC high side pressure, or coolant temp.
I'm amazed at the variety of different fan operation schemes there are out there, even just within Chrysler. The first electric-fan vehicle I owned that did anything more complicated than turning the fan on (one speed) when the AC was on or the engine got hot was my wife's 93 LH. It had 2 speeds, and the fans were operated very indirectly by the AC system. Running down the road, the fans might never run at all because they were strictly triggered by condenser pressure or engine temp. If there was enough air without the fans, they just wouldn't run. Higher water temp or higher condenser pressure would kick the fans to high speed, and boy would that fan set move some air. They also had a unique 2-note tone- I used to always be able to identify LH cars by sound of the twin fans before I'd even see them.
The PT and the Ram on the other hand obviously run the fan for no apparent reason at all on startup- I suppose blowing fuel vapors and hydrogen fumes from the battery out of the engine compartment might be a valid reason. The fans then shut off until needed. The Ram is even odder (to me) in that its electric fan ONLY moves air over the AC condenser- the radiator has an engine-driven fan so what good does it do to run the electric fan for ~30 seconds on engine start in addition to the engine-driven fan?
Even my 2 Jeeps use different schemes. Both turn the electric fan on if the engine gets above normal operating temp. But the '99 has the electric fan slaved to the compressor clutch when the AC is on. The 01 doesn't- if the engine-driven fan is sufficient to keep the condenser pressure down, it doesn't bother with the electric fan.
yes, modern vehicles run the fans for a variety of reasons.
I was quite surprised that the same parameters trigger the PT fans as trigger my LX. On mine, the fans run at low all the time if climate control is on. I get a high speed burst when first started after a heat soak. Then I can get high speed for trans temp, AC high side pressure, or coolant temp.
I'm amazed at the variety of different fan operation schemes there are out there, even just within Chrysler. The first electric-fan vehicle I owned that did anything more complicated than turning the fan on (one speed) when the AC was on or the engine got hot was my wife's 93 LH. It had 2 speeds, and the fans were operated very indirectly by the AC system. Running down the road, the fans might never run at all because they were strictly triggered by condenser pressure or engine temp. If there was enough air without the fans, they just wouldn't run. Higher water temp or higher condenser pressure would kick the fans to high speed, and boy would that fan set move some air. They also had a unique 2-note tone- I used to always be able to identify LH cars by sound of the twin fans before I'd even see them.
The PT and the Ram on the other hand obviously run the fan for no apparent reason at all on startup- I suppose blowing fuel vapors and hydrogen fumes from the battery out of the engine compartment might be a valid reason. The fans then shut off until needed. The Ram is even odder (to me) in that its electric fan ONLY moves air over the AC condenser- the radiator has an engine-driven fan so what good does it do to run the electric fan for ~30 seconds on engine start in addition to the engine-driven fan?
Even my 2 Jeeps use different schemes. Both turn the electric fan on if the engine gets above normal operating temp. But the '99 has the electric fan slaved to the compressor clutch when the AC is on. The 01 doesn't- if the engine-driven fan is sufficient to keep the condenser pressure down, it doesn't bother with the electric fan.
