98 deville no heater blower operation

[lestro]

I have a 98 deville with hvac problems, no blower operation. I have replaced the blower motor with a new one twice, replaced the acm (with used ones )twice, I have 12v and ground at the blower motor,9v to 4 v on the center wire depending on the fan speed setting and even ran a temporary wire ckt 754 from acm to to motor. No trouble codes showing with onboard diag. I check for blower with engine running at operating temp, temp setting at 90 and fan on hi. I've checked all fuses in trunk and under hood. The only other thing I can think of, is ,I'm not sure I can hear the heater doors operating.... Anybody got any ideas? thanks

[Cadillac Jim]

The first thing you need to do is run the OBD codes. The codes will tell you what is wrong. Never throw parts at a car without diagnosing the problem first.

See the link in my signature block for instructions.

[rockfangd]

thread shows user did check onboard codes. Maybe we can confirm all of the systems were checked.

If the problem was a blend door problem the blower would still work fine. I would check to be sure the fuses have proper voltage and that there is no corrosion in the pins for the fuses. Best of luck to you.

What blower motor did you install? there are a few different types out there. Most common replacement is the plastic one with the shield

[Cadillac Jim]

The blower motor has power and ground to it at all times. It takes its orders from the heater and A/C programmer through the GRY wire. The heater and A/C programmer gets its orders over the car's network, the PPL/WHT wire. Power to the heater and A/C programmer comes through the 10 Amp IGN0-BODY fuse in the trunk compartment fuse block, and his hot only with the key on.

If the blower motor is running but you have no air through the vents, you may have a vacuum line off under the dash. A quick check is to put the emergency brake on in Park, start the engine, and move the shifter out of Park. If the emergency brake releases automatically, you have vacuum through the A/C programmer.

Main blower power is through the 50 Amp INDVET FUSE, which at 50 Amps is a Maxifuse. But you already said that you have 12 Volts at the blower motor.

[KHE]

What does the blower motor connector on the harness look like? Sometimes, they get overheated and melt and do not make contact with the blower. If that is the case, I believe a repair pigtail is available. When the blower system is fixed, make sure the foil/fiberglass heat shield is installed otherwise, the blower won't last. The shield used to be included with the replacement blower but it is now sold separately.

[rockfangd]

both nailed very specific details. Some people dont even know about the trunk fuse panel.

I have had the connector melt before.

[lestro]

thread shows user did check onboard codes. Maybe we can confirm all of the systems were checked.

If the problem was a blend door problem the blower would still work fine. I would check to be sure the fuses have proper voltage and that there is no corrosion in the pins for the fuses. Best of luck to you.

What blower motor did you install? there are a few different types out there. Most common replacement is the plastic one with the shield

thanks, I used the tyc 700108 through amazon, both new ones. Although I did check all the fuses with a vom. I did not read the voltages through them

[lestro]

The blower motor has power and ground to it at all times. It takes its orders from the heater and A/C programmer through the GRY wire. The heater and A/C programmer gets its orders over the car's network, the PPL/WHT wire. Power to the heater and A/C programmer comes through the 10 Amp IGN0-BODY fuse in the trunk compartment fuse block, and his hot only with the key on.

If the blower motor is running but you have no air through the vents, you may have a vacuum line off under the dash. A quick check is to put the emergency brake on in Park, start the engine, and move the shifter out of Park. If the emergency brake releases automatically, you have vacuum through the A/C programmer.

Main blower power is through the 50 Amp INDVET FUSE, which at 50 Amps is a Maxifuse. But you already said that you have 12 Volts at the blower motor.

thanks,I had 12v and ground, but I even ran them from the battery to the motor side of plug, also a temporary wire from center wire to acm, no blower.The puzzling thing to me is that I have 9v to 4v on center wire at blower motor, depending on fan setting. I don't have an oscilloscope to check for modulation

[lestro]

What does the blower motor connector on the harness look like? Sometimes, they get overheated and melt and do not make contact with the blower. If that is the case, I believe a repair pigtail is available. When the blower system is fixed, make sure the foil/fiberglass heat shield is installed otherwise, the blower won't last. The shield used to be included with the replacement blower but it is now sold separately.

Thanks, the plug looked fine, checked it with an ohmmeter, checked fine, even bypassed it just to make sure. These tyc motors had a shield with them.

[KHE]

The blower motor operates on a pulse width modulated signal in order to have infinite speeds. If you have access to an oscilloscope, you could monitor the signal on the grey wire while to adjust the speed. If the signal checks out OK, then the ACM is good and it would point to the blower.

Do you know anyone with a similar car that you could plug your blower motor into to see if it works? That would be a quick way to test the blower motor. From the posts, it sounds like an aftermarket blower is being used.

[lestro]

The blower motor operates on a pulse width modulated signal in order to have infinite speeds. If you have access to an oscilloscope, you could monitor the signal on the grey wire while to adjust the speed. If the signal checks out OK, then the ACM is good and it would point to the blower.

Do you know anyone with a similar car that you could plug your blower motor into to see if it works? That would be a quick way to test the blower motor. From the posts, it sounds like an aftermarket blower is being

Thanks for the input. i don't have access to a scope, and although it could happen, the odds of 2 new motors being badwould be surprising. I don't know of another car around here that I could substitute.

[Cadillac Jim]

The fact that your DVM reads 9 Volts to 4 Volts at the gray wire tells me that the signal from the A/C programmer is good. I checked the listing on Amazon and these do have a "limited lifetime warranty." Since you have two that don't work, I would call the seller and ask them what's up before you return the second one. I suspect that the gray wire terminal is static sensitive and they didn't tell you that.

But first I would check and make sure that the connector is getting all the wires hooked firmly to the motor. That seems likely the problem and it is a lot easier to change a connector on the wiring harness than to R&R the blower motor.

[rockfangd]

Just curious how did you go about replacing the motors? did you move the engine forward? any install issues?

[KHE]

I agree with Jim - you have the correct signals at the blower - either the connector is not making contact or you have a bad blower motor assembly

[lestro]

Just curious how did you go about replacing the motors? did you move the engine forward? any install issues?

The first time I tried, I attempted to pull the engine forward, but that didn't give enough clearance, so I lowered the front of the engine cradle. Plenty of clearance, no problems.

[lestro]

The fact that your DVM reads 9 Volts to 4 Volts at the gray wire tells me that the signal from the A/C programmer is good. I checked the listing on Amazon and these do have a "limited lifetime warranty." Since you have two that don't work, I would call the seller and ask them what's up before you return the second one. I suspect that the gray wire terminal is static sensitive and they didn't tell you that.

But first I would check and make sure that the connector is getting all the wires hooked firmly to the motor. That seems likely the problem and it is a lot easier to change a connector on the wiring harness than to R&R the blower motor.

I bypassed that plug, didn't make any difference. I had come to think the motor was bad also ,butjust figured I was doing something stupid

[Cadillac Jim]

You need to bypass the gray wire to the A/C controller that has the PWM digital signal on it. This is the wire that your DVM reads 9 Volts to 4 Volts on. This is the wire that tells the motor to turn on.

[lestro]

You need to bypass the gray wire to the A/C controller that has the PWM digital signal on it. This is the wire that your DVM reads 9 Volts to 4 Volts on. This is the wire that tells the motor to turn on.

Thanks, I ran a temporary wire directly from the acm. the readings were taken from the wires on the motor side of the plug

[Cadillac Jim]

Well, if it has power, it has ground, and it has signal, it *should* work. Time for another.

You can do yet another check on the gray wire: read the A/C voltage. That, with the DC voltage, will give you a hint of the pulse train.